Science.gov

Sample records for switch mode dc-dc

  1. Symmetrical dynamics of peak current-mode and valley current-mode controlled switching dc-dc converters with ramp compensation

    NASA Astrophysics Data System (ADS)

    Zhou, Guo-Hua; Xu, Jian-Ping; Bao, Bo-Cheng; Jin, Yan-Yan

    2010-06-01

    The discrete iterative map models of peak current-mode (PCM) and valley current-mode (VCM) controlled buck converters, boost converters, and buck-boost converters with ramp compensation are established and their dynamical behaviours are investigated by using the operation region, parameter space map, bifurcation diagram, and Lyapunov exponent spectrum. The research results indicate that ramp compensation extends the stable operation range of the PCM controlled switching dc-dc converter to D > 0.5 and that of the VCM controlled switching dc-dc converter to D < 0.5. Compared with PCM controlled switching dc-dc converters with ramp compensation, VCM controlled switching dc-dc converters with ramp compensation exhibit interesting symmetrical dynamics. Experimental results are given to verify the analysis results in this paper.

  2. Soft switching active snubbers for DC/DC converters

    SciTech Connect

    Elasser, A.; Torrey, D.A.

    1996-09-01

    A soft-switching active snubber is proposed to reduce the turn-off losses of the insulated gate bipolar transistor (IGBT) in a buck converter. The soft-switching snubber provides zero-voltage switching for the IGBT, thereby reducing its high turn-off losses due to the current tailing. The proposed snubber uses an auxiliary switch to discharge the snubber capacitor. This auxiliary switch also operates at zero-voltage and zero-current switching. The size of the auxiliary switch compared to the main switch makes this snubber a good alternative to the conventional snubber or even to passive low-loss snubbers. The use of the soft-switching active snubber permits the IGBT to operate at high frequencies with an improved RBSOA. In the experimental results reported for a 1 kW, 40 kHz prototype, combined switching/snubbing losses are reduced by 36% through the use of the active snubber compared to a conventional RCD snubber. The use of an active snubber capacitor during turn-off. The generic snubber cell for the buck converter is generalized to support the common nonisolated dc/dc converters (buck, boost, buck-boost, Cuk, sepic, zeta) as well as isolated dc/dc converters (forward, flyback, Cuk, and sepic).

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  4. Switching coordination of distributed dc-dc converters for highly efficient photovoltaic power plants

    DOEpatents

    Agamy, Mohammed; Elasser, Ahmed; Sabate, Juan Antonio; Galbraith, Anthony William; Harfman Todorovic, Maja

    2014-09-09

    A distributed photovoltaic (PV) power plant includes a plurality of distributed dc-dc converters. The dc-dc converters are configured to switch in coordination with one another such that at least one dc-dc converter transfers power to a common dc-bus based upon the total system power available from one or more corresponding strings of PV modules. Due to the coordinated switching of the dc-dc converters, each dc-dc converter transferring power to the common dc-bus continues to operate within its optimal efficiency range as well as to optimize the maximum power point tracking in order to increase the energy yield of the PV power plant.

  5. State space analysis of boost DC/DC converter with voltage mode control

    NASA Astrophysics Data System (ADS)

    Shenoy, K. Latha; Nayak, C. Gurudas; Mandi, Rajashekar P.

    2017-07-01

    The boost converter belongs to the family of indirect energy transfer converters. The inductor stores energy during switch on and the output capacitor deliver power to the load. During switch off condition, the stored inductive energy appears in series with the input source and supply the output. The paper deals with the small signal analysis of dc-dc boost converter. It is used in modeling the closed loop converter parameters. The boost converter produces an undesirable Right-Half Plane Zero (RHPZ) in the small signal analysis due to which the implementation of voltage mode control needs attention. This requires compensating the regulator such that the crossover frequency occurs well below the frequency of the RHP zero. The paper describes modeling of voltage mode control boost converter operating in continuous conduction mode.

  6. Switched capacitor DC-DC converter ASICs for the upgraded LHC trackers

    NASA Astrophysics Data System (ADS)

    Bochenek, M.; Dabrowski, W.; Faccio, F.; Michelis, S.

    2010-12-01

    The High Luminosity Upgrade of the ATLAS Inner Tracker puts demanding requirements on the powering system of the silicon strip detector modules due to 10-fold increase of the channel count compared to the existing SemiConductor Tracker. Therefore, new solutions for the powering scheme must be elaborated. Currently two possible approaches, the serial powering and the parallel powering scheme using the DC-DC conversion technique, are under development. This paper describes two switched capacitor DC-DC converters designed in a 130 nm technology. For the optimized step-down converter, foreseen for the parallel powering scheme, power efficiency of 97% has been achieved, while for the charge pump, designed for the serial powering scheme, power efficiency of 85% has been achieved.

  7. A three-phase soft-switched high-power-density dc/dc converter for high power applications

    SciTech Connect

    DeDoncker, R.W.A.A. ); Divan, D.M.; Kheraluwala, M.H. )

    1991-01-01

    In this paper three dc/dc converter topologies suitable for high-power-density high-power applications are presented. All three circuits operate in a soft-switched manner, making possible a reduction in device switching losses and an increase in switching frequency. The three-phase dual-bridge converter proposed is seen to have the most favorable characteristics. This converter consists of two three-phase inverter stages operating in a high-frequency six-step mode. In contrast to existing single-phase ac-link dc/dc converters, lower turn-off peak currents in the power devices and lower rms current ratings for both the input and output filter capacitors are obtained. This is in addition to smaller filter element values due to the higher-frequency content of the input and output waveforms. Furthermore, the use of a three phase symmetrical transformer instead of single-phase transformers and a better utilization of the available apparent power of the transformer (as a consequence of the controlled output inverter) significantly increase the power density attainable.

  8. Radiation effects in power converters: Design of a radiation hardened integrated switching DC/DC converter

    NASA Astrophysics Data System (ADS)

    Adell, Philippe

    When electronic devices are used in space and military systems, they may be exposed to various types of radiation, including photons, electrons, protons, neutrons, and heavy ions. The effects of radiation on the semiconductor devices within the systems range from gradual degradation to catastrophic failure. In order to design and produce reliable systems for space or military applications, it is necessary to understand the device-level effects of radiation and develop appropriate strategies for reducing system susceptibility. This research focuses on understanding radiation effects in power converters for space and military applications. We show that power converters are very sensitive to radiation (total-dose, single event effects and displacement damage) and that their radiation response is dependent on input bias conditions and load conditions. We compared the radiation hardness of various power converter topologies using experiments and simulations. Evaluation of these designs under different modes of operation is demonstrated to be critical for determining radiation hardness. We emphasize the correlation between radiation effects and the role of the dynamic response of these topologies. For instance, total dose exposure has been found to degrade loop gain and affect regulation in some converters. We propose several radiation-hardening solutions to improve the radiation response of these designs. For instance, we demonstrate the design of a digitally controlled boost converter suitable for space applications based on an SRAM FPGA. A design hardening solution has been developed and successfully applied through VHDL simulations and experiments to assure the continuous operation of the converter in the presence of SEES (more precisely SEFIs). This research led to the design of a digitally controlled radiation hardened integrated switching buck converter. The proposed design is suitable for micro-satellite applications and is based on a high-voltage/CMOS process

  9. A Compact, Soft-Switching DC-DC Converter for Electric Propulsion

    NASA Technical Reports Server (NTRS)

    Button, Robert; Redilla, Jack; Ayyanar, Raja

    2003-01-01

    A hybrid, soft-switching, DC-DC converter has been developed with superior soft switching characteristics, high efficiency, and low electro-magnetic interference. This hybrid topology is comprised of an uncontrolled bridge operating at full pulse-width, and a controlled section operating as a conventional phase modulated converter. The unique topology is able to maintain zero voltage switching down to no load operating conditions. A breadboard prototype was developed and tested to demonstrate the benefits of the topology. Improvements were then made to reduce the size of passive components and increase efficiency in preparation for packaging. A packaged prototype was then designed and built, and several innovative packaging techniques are presented. Performance test data is presented that reveals deficiencies in the design of the power transformer. A simple redesign of the transformer windings eliminated the deficiency. Future plans to improve the converter and packaging design are presented along with several conclusions.

  10. A Compact, Soft-Switching DC-DC Converter for Electric Propulsion

    NASA Technical Reports Server (NTRS)

    Button, Robert; Redilla, Jack; Ayyanar, Raja

    2003-01-01

    A hybrid, soft-switching, DC-DC converter has been developed with superior soft switching characteristics, high efficiency, and low electro-magnetic interference. This hybrid topology is comprised of an uncontrolled bridge operating at full pulse-width, and a controlled section operating as a conventional phase modulated converter. The unique topology is able to maintain zero voltage switching down to no load operating conditions. A breadboard prototype was developed and tested to demonstrate the benefits of the topology. Improvements were then made to reduce the size of passive components and increase efficiency in preparation for packaging. A packaged prototype was then designed and built, and several innovative packaging techniques are presented. Performance test data is presented that reveals deficiencies in the design of the power transformer. A simple redesign of the transformer windings eliminated the deficiency. Future plans to improve the converter and packaging design are presented along with several conclusions.

  11. An Integrated Programmable Wide-range PLL for Switching Synchronization in Isolated DC-DC Converters

    NASA Astrophysics Data System (ADS)

    Fard, Miad

    In this thesis, two Phase-Locked-Loop (PLL) based synchronization schemes are introduced and applied to a bi-directional Dual-Active-Bridge (DAB) dc-dc converter with an input voltage up to 80 V switching in the range of 250 kHz to 1 MHz. The two schemes synchronize gating signals across an isolated boundary without the need for an isolator per transistor. The Power Transformer Sensing (PTS) method utilizes the DAB power transformer to indirectly sense switching on the secondary side of the boundary, while the Digital Isolator Sensing (DIS) method utilizes a miniature transformer for synchronization and communication at up to 100 MHz. The PLL is implemented on-chip, and is used to control an external DAB power-stage. This work will lead to lower cost, high-frequency isolated dc-dc converters needed for a wide variety of emerging low power applications where isolator cost is relatively high and there is a demand for the reduction of parts.

  12. Finite-time control of DC-DC buck converters via integral terminal sliding modes

    NASA Astrophysics Data System (ADS)

    Chiu, Chian-Song; Shen, Chih-Teng

    2012-05-01

    This article presents novel terminal sliding modes for finite-time output tracking control of DC-DC buck converters. Instead of using traditional singular terminal sliding mode, two integral terminal sliding modes are introduced for robust output voltage tracking of uncertain buck converters. Different from traditional sliding mode control (SMC), the proposed controller assures finite convergence time for the tracking error and integral tracking error. Furthermore, the singular problem in traditional terminal SMC is removed from this article. When considering worse modelling, adaptive integral terminal SMC is derived to guarantee finite-time convergence under more relaxed stability conditions. In addition, several experiments show better start-up performance and robustness.

  13. A dual VCDL DLL based gate driver for zero-voltage-switching DC-DC converter

    NASA Astrophysics Data System (ADS)

    Xin, Tian; Xiangxin, Liu; Wenhong, Li

    2010-07-01

    This paper presents a dual voltage-controlled-delay-line (VCDL) delay-lock-loop (DLL) based gate driver for a zero-voltage-switching (ZVS) DC-DC converter. Using the delay difference of two VCDLs for the dead time control, the dual VCDL DLL is able to implement ZVS control with high accuracy while keeping good linearity performance of the DLL and low power consumption. The design is implemented in the CSM 2P4M 0.35 μm CMOS process. The measurement results indicate that an efficiency improvement of 2%-4% is achieved over the load current range from 100 to 600 mA at 4 MHz switching frequency with 3.3 V input and 1.3 V output voltage.

  14. Sliding-mode control of single input multiple output DC-DC converter

    NASA Astrophysics Data System (ADS)

    Zhang, Libo; Sun, Yihan; Luo, Tiejian; Wan, Qiyang

    2016-10-01

    Various voltage levels are required in the vehicle mounted power system. A conventional solution is to utilize an independent multiple output DC-DC converter whose cost is high and control scheme is complicated. In this paper, we design a novel SIMO DC-DC converter with sliding mode controller. The proposed converter can boost the voltage of a low-voltage input power source to a controllable high-voltage DC bus and middle-voltage output terminals, which endow the converter with characteristics of simple structure, low cost, and convenient control. In addition, the sliding mode control (SMC) technique applied in our converter can enhance the performances of a certain SIMO DC-DC converter topology. The high-voltage DC bus can be regarded as the main power source to the high-voltage facility of the vehicle mounted power system, and the middle-voltage output terminals can supply power to the low-voltage equipment on an automobile. In the respect of control algorithm, it is the first time to propose the SMC-PID (Proportion Integration Differentiation) control algorithm, in which the SMC algorithm is utilized and the PID control is attended to the conventional SMC algorithm. The PID control increases the dynamic ability of the SMC algorithm by establishing the corresponding SMC surface and introducing the attached integral of voltage error, which endow the sliding-control system with excellent dynamic performance. At last, we established the MATLAB/SIMULINK simulation model, tested performance of the system, and built the hardware prototype based on Digital Signal Processor (DSP). Results show that the sliding mode control is able to track a required trajectory, which has robustness against the uncertainties and disturbances.

  15. Sliding-mode control of single input multiple output DC-DC converter.

    PubMed

    Zhang, Libo; Sun, Yihan; Luo, Tiejian; Wan, Qiyang

    2016-10-01

    Various voltage levels are required in the vehicle mounted power system. A conventional solution is to utilize an independent multiple output DC-DC converter whose cost is high and control scheme is complicated. In this paper, we design a novel SIMO DC-DC converter with sliding mode controller. The proposed converter can boost the voltage of a low-voltage input power source to a controllable high-voltage DC bus and middle-voltage output terminals, which endow the converter with characteristics of simple structure, low cost, and convenient control. In addition, the sliding mode control (SMC) technique applied in our converter can enhance the performances of a certain SIMO DC-DC converter topology. The high-voltage DC bus can be regarded as the main power source to the high-voltage facility of the vehicle mounted power system, and the middle-voltage output terminals can supply power to the low-voltage equipment on an automobile. In the respect of control algorithm, it is the first time to propose the SMC-PID (Proportion Integration Differentiation) control algorithm, in which the SMC algorithm is utilized and the PID control is attended to the conventional SMC algorithm. The PID control increases the dynamic ability of the SMC algorithm by establishing the corresponding SMC surface and introducing the attached integral of voltage error, which endow the sliding-control system with excellent dynamic performance. At last, we established the MATLAB/SIMULINK simulation model, tested performance of the system, and built the hardware prototype based on Digital Signal Processor (DSP). Results show that the sliding mode control is able to track a required trajectory, which has robustness against the uncertainties and disturbances.

  16. Sliding mode controller with modified sliding function for DC-DC Buck Converter.

    PubMed

    Naik, B B; Mehta, A J

    2017-09-01

    This article presents design of Sliding Mode Controller with proportional integral type sliding function for DC-DC Buck Converter for the controlled power supply. The converter with conventional sliding mode controller results in a steady state error in load voltage. The proposed modified sliding function improves the steady state and dynamic performance of the Convertor and facilitates better choices of controller tuning parameters. The conditions for existence of sliding modes for proposed control scheme are derived. The stability of the closed loop system with proposed sliding mode control is proved and improvement in steady state performance is exemplified. The idea of adaptive tuning for the proposed controller to compensate load variations is outlined. The comparative study of conventional and proposed control strategy is presented. The efficacy of the proposed strategy is endowed by the simulation and experimental results. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  17. A novel asymmetrical duty-cycle soft-switching DC-DC converter with lower conduction losses than in hard-switched PWM converters

    SciTech Connect

    Imbertson, P.; Mohan, N.

    1995-12-31

    An asymmetrical duty-cycle dc-dc power converter was proposed recently, which allows zero-voltage switching while keeping the switch conduction losses as low as in standard hard switched PWM converters. Further developments now allow the asymmetrical circuit to exhibit lower conduction losses than standard PWM circuits.

  18. A novel PWM control for a bi-directional full-bridge DC-DC converter with smooth conversion mode transitions

    NASA Astrophysics Data System (ADS)

    Lorentz, V. R. H.; Schwarzmann, H.; März, M.; Bauer, A. J.; Ryssel, H.; Frey, L.; Poure, P.; Braun, F.

    2011-08-01

    A novel CMOS integrated pulse-width modulation (PWM) control circuit allowing smooth transitions between conversion modes in full-bridge based bi-directional DC-DC converters operating at high switching frequencies is presented. The novel PWM control circuit is able to drive full-bridge based DC-DC converters performing step-down (i.e. buck) and step-up (i.e. boost) voltage conversion in both directions, thus allowing charging and discharging of the batteries in mobile systems. It provides smooth transitions between buck, buck-boost and boost modes. Additionally, the novel PWM control loop circuit uses a symmetrical triangular carrier, which overcomes the necessity of using an output phasing circuit previously required in PWM controllers based on sawtooth oscillators. The novel PWM control also enables to build bi-directional DC-DC converters operating at high switching frequencies (i.e. up to 10 MHz and above). Finally, the proposed PWM control circuit also allows the use of an average lossless inductor-current sensor for sensing the average load current even at very high switching frequencies. In this article, the proposed PWM control circuit is modelled and the integrated CMOS schematic is given. The corresponding theory is analysed and presented in detail. The circuit simulations realised in the Cadence Spectre software with a commercially available 0.18 µm mixed-signal CMOS technology from UMC are shown. The PWM control circuit was implemented in a monolithic integrated bi-directional CMOS DC-DC converter ASIC prototype. The fabricated prototype was tested experimentally and has shown performances in accordance with the theory.

  19. Adaptive terminal sliding-mode control strategy for DC-DC buck converters.

    PubMed

    Komurcugil, Hasan

    2012-11-01

    This paper presents an adaptive terminal sliding mode control (ATSMC) strategy for DC-DC buck converters. The idea behind this strategy is to use the terminal sliding mode control (TSMC) approach to assure finite time convergence of the output voltage error to the equilibrium point and integrate an adaptive law to the TSMC strategy so as to achieve a dynamic sliding line during the load variations. In addition, the influence of the controller parameters on the performance of closed-loop system is investigated. It is observed that the start up response of the output voltage becomes faster with increasing value of the fractional power used in the sliding function. On the other hand, the transient response of the output voltage, caused by the step change in the load, becomes faster with decreasing the value of the fractional power. Therefore, the value of fractional power is to be chosen to make a compromise between start up and transient responses of the converter. Performance of the proposed ATSMC strategy has been tested through computer simulations and experiments. The simulation results of the proposed ATSMC strategy are compared with the conventional SMC and TSMC strategies. It is shown that the ATSMC exhibits a considerable improvement in terms of a faster output voltage response during load changes.

  20. A Design Methodology for Switched-Capacitor DC-DC Converters

    DTIC Science & Technology

    2009-05-21

    control PCB VIN L VOUT C0 C1 C3 C5 C2 C4 C16 LT1615-1 VIN SW SHDN FB GND R1 R2 CIN Figure 6.5. Hybrid SC boost converter as appearing on the MicroGlider...B. A. Bloechel, P. Hack , G. Dermer, S. G. Narendra, D. S. Gardner, T. Karnik, V. De, and S. Borkar, “A 233-mhz 80%-87% efficient four- phase dc-dc

  1. Analysis and modeling of a two-input DC/DC converter with two controlled variables and four switched networks

    SciTech Connect

    Rodriguez, F.D.; Imes, W.G.

    1996-12-31

    Recently, a two-input tri-state DC/DC converter was presented capable of performing solar array peak-power tracking, battery power conditioning, and output voltage regulation all within the same converter structure. At light loads and during periods of low insolation, converter operation will naturally evolve through four linear switched networks. In this paper, the small-signal stability of the tri-state converter is analyzed and a large-signal averaged model is derived capable of predicting the dynamic behavior during and following transitions to and from this fourth state.

  2. Multiphase soft switched DC/DC converter and active control technique for fuel cell ripple current elimination

    SciTech Connect

    Lai, Jih-Sheng; Liu, Changrong; Ridenour, Amy

    2009-04-14

    DC/DC converter has a transformer having primary coils connected to an input side and secondary coils connected to an output side. Each primary coil connects a full-bridge circuit comprising two switches on two legs, the primary coil being connected between the switches on each leg, each full-bridge circuit being connected in parallel wherein each leg is disposed parallel to one another, and the secondary coils connected to a rectifying circuit. An outer loop control circuit that reduces ripple in a voltage reference has a first resistor connected in series with a second resistor connected in series with a first capacitor which are connected in parallel with a second capacitor. An inner loop control circuit that reduces ripple in a current reference has a third resistor connected in series with a fourth resistor connected in series with a third capacitor which are connected in parallel with a fourth capacitor.

  3. Milliwatt dc/dc Inverter

    NASA Technical Reports Server (NTRS)

    Mclyman, C. W.

    1983-01-01

    Compact dc/dc inverter uses single integrated-circuit package containing six inverter gates that generate and amplify 100-kHz square-wave switching signal. Square-wave switching inverts 10-volt local power to isolated voltage at another desired level. Relatively high operating frequency reduces size of filter capacitors required, resulting in small package unit.

  4. Cascaded transformerless DC-DC voltage amplifier with optically isolated switching devices

    NASA Technical Reports Server (NTRS)

    Sridharan, Govind (Inventor)

    1993-01-01

    A very high voltage amplifier is provided in which plural cascaded banks of capacitors are switched by optically isolated control switches so as to be charged in parallel from the preceding stage or capacitor bank and to discharge in series to the succeeding stage or capacitor bank in alternating control cycles. The optically isolated control switches are controlled by a logic controller whose power supply is virtually immune to interference from the very high voltage output of the amplifier by the optical isolation provided by the switches, so that a very high voltage amplification ratio may be attained using many capacitor banks in cascade.

  5. Analytical and Practical Analysis of Switched-Capacitor DC-DC Converters

    DTIC Science & Technology

    2006-09-01

    switches between these two frequency levels to keep the voltage on the output capacitor between two hysteresis levels vhi and vlo. These voltages are...defined to be slightly higher and slightly lower than the desired output voltage. When the output voltage exceeds vhi , the switching frequency is set

  6. Bidirectional DC/DC Converter

    NASA Astrophysics Data System (ADS)

    Pedersen, F.

    2008-09-01

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

  7. Switching performance and efficiency investigation of GaN based DC-DC Buck converter for low voltage and high current applications

    NASA Astrophysics Data System (ADS)

    Alatawi, Khaled; Almasoudi, Fahad; Matin, Mohammad

    2016-09-01

    The Wide band-gap (WBG) materials "such as Silicon Carbide (SiC) and Gallium nitride (GaN)" based power switching devices provide higher performance capabilities compared to Si-based power switching devices. The wide band-gap materials based power switching devices outperform Si-based devices in many performance characteristics such as: low witching loss, low conduction loss, high switching frequencies, and high operation temperature. GaN based switching devices benefit a lot of applications such as: future electric vehicles and solar power inverters. In this paper, a DC-DC Buck converter based on GaN FET for low voltage and high current applications is designed and investigated. The converter is designed for stepping down a voltage of 48V to 12V with high switching frequency. The capability of the GaN FET based buck converter is studied and compared to equivalent SiC MOSFET and Si-based MOSFET buck converters. The analysis of switching losses and efficiency was performed to compare the performance capabilities of GaN FET, SiC MOSFET and Si-based MOSFET. The results showed that the overall switching losses of GaN FET are lower than that of SiC and Si-based power switching devices. Also, the performance capability of GaN devices with higher frequencies is studied. GaN devices with high frequencies will reduce the total size and the cost of the power converter. In Addition, the overall efficiency of the DC-DC Buck converter is higher with the GaN FET switching devices, which make it more suitable for low voltage and high current applications.

  8. Early Oscillation Detection Technique for Hybrid DC/DC Converters

    NASA Technical Reports Server (NTRS)

    Wang, Bright L.

    2011-01-01

    Oscillation or instability is a situation that must be avoided for reliable hybrid DC/DC converters. A real-time electronics measurement technique was developed to detect catastrophic oscillations at early stages for hybrid DC/DC converters. It is capable of identifying low-level oscillation and determining the degree of the oscillation at a unique frequency for every individual model of the converters without disturbing their normal operations. This technique is specially developed for space-used hybrid DC/DC converters, but it is also suitable for most of commercial and military switching-mode power supplies. This is a weak-electronic-signal detection technique to detect hybrid DC/DC converter oscillation presented as a specific noise signal at power input pins. It is based on principles of feedback control loop oscillation and RF signal modulations, and is realized by using signal power spectral analysis. On the power spectrum, a channel power amplitude at characteristic frequency (CPcf) and a channel power amplitude at switching frequency (CPsw) are chosen as oscillation level indicators. If the converter is stable, the CPcf is a very small pulse and the CPsw is a larger, clear, single pulse. At early stage of oscillation, the CPcf increases to a certain level and the CPsw shows a small pair of sideband pulses around it. If the converter oscillates, the CPcf reaches to a higher level and the CPsw shows more high-level sideband pulses. A comprehensive stability index (CSI) is adopted as a quantitative measure to accurately assign a degree of stability to a specific DC/DC converter. The CSI is a ratio of normal and abnormal power spectral density, and can be calculated using specified and measured CPcf and CPsw data. The novel and unique feature of this technique is the use of power channel amplitudes at characteristic frequency and switching frequency to evaluate stability and identify oscillations at an early stage without interfering with a DC/DC converter s

  9. High power density dc/dc converter: Selection of converter topology

    NASA Technical Reports Server (NTRS)

    Divan, Deepakraj M.

    1990-01-01

    The work involved in the identification and selection of a suitable converter topology is described. Three new dc/dc converter topologies are proposed: Phase-Shifted Single Active Bridge DC/DC Converter; Single Phase Dual Active Bridges DC/DC Converter; and Three Phase Dual Active Bridges DC/DC Converter (Topology C). The salient features of these topologies are: (1) All are minimal in structure, i.e., each consists of an input and output bridge, input and output filter and a transformer, all components essential for a high power dc/dc conversion process; (2) All devices of both the bridges can operate under near zero-voltage conditions, making possible a reduction of device switching losses and hence, an increase in switching frequency; (3) All circuits operate at a constant frequency, thus simplifying the task of the magnetic and filter elements; (4) Since, the leakage inductance of the transformer is used as the main current transfer element, problems associated with the diode reverse recovery are eliminated. Also, this mode of operation allows easy paralleling of multiple modules for extending the power capacity of the system; (5) All circuits are least sensitive to parasitic impedances, infact the parasitics are efficently utilized; and (6) The soft switching transitions, result in low electromagnetic interference. A detailed analysis of each topology was carried out. Based on the analysis, the various device and component ratings for each topology operating at an optimum point, and under the given specifications, are tabulated and discussed.

  10. On-chip frequency compensation with a dual signal path operational transconductance amplifier for a voltage mode control DC/DC converter

    NASA Astrophysics Data System (ADS)

    Qiang, Ye; Jie, Liu; Bing, Yuan; Xinquan, Lai; Ning, Liu

    2012-04-01

    A novel on-chip frequency compensation circuit for a voltage-mode control DC/DC converter is presented. By employing an RC network in the two signal paths of an operational transconductance amplifier (OTA), the proposed circuit generates two zeros to realize high closed-loop stability. Meanwhile, full on-chip integration is also achieved due to its simple structure. Hence, the number of off-chip components and the board space is greatly reduced. The structure of the dual signal path OTA is also optimized to help get a better transition response. Implemented in a 0.5 μm CMOS process, the voltage mode control DC/DC converter with the proposed frequency compensation circuit exhibits good stability. The test results show that both load and line regulations are less than 0.3%, and the output voltage can be recovered within 15 μs for a 400 mA load step. Moreover, the compensation components area is less than 2% of the die's area and the board space is also reduced by 11%. The efficiency of the whole chip can be up to 95%.

  11. Nonlinear Phenomena and Resonant Parametric Perturbation Control in QR-ZCS Buck DC-DC Converters

    NASA Astrophysics Data System (ADS)

    Hsieh, Fei-Hu; Liu, Feng-Shao; Hsieh, Hui-Chang

    The purpose of this study is to investigate the chaotic phenomena and to control in current-mode controlled quasi-resonant zero-current-switching (QR-ZCS) DC-DC buck converters, and to present control of chaos by resonant parametric perturbation control methods. First of all, MATLAB/SIMULINK is used to derive a mathematical model for QR-ZCS DC-DC buck converters, and to simulate the converters to observe the waveform of output voltages, inductance currents and phase-plane portraits from the period-doubling bifurcation to chaos by changing the load resistances. Secondly, using resonant parametric perturbation control in QR-ZCS buck DC-DC converters, the simulation results of the chaotic converter form chaos state turn into stable state period 1, and improve ripple amplitudes of converters under the chaos, to verify the validity of the proposes method.

  12. A unified analysis and design procedure for a standardized control module for dc-dc switching regulators

    NASA Technical Reports Server (NTRS)

    Lee, F. C.; Yu, Y.; Mahmoud, M. F.

    1980-01-01

    Three basic switching regulators: buck, boost, and buck/boost, employing a multi-loop control module (SCM) were characterized by a common small signal block diagram. Employing the unified model, regulator performances such as stability, audiosusceptibility, output impedance and step load transient are analyzed and key performance indexes are expressed in simple analytical forms. More importantly, the performance characteristics of all three regulators are shown to enjoy common properties due to the unique SCM control scheme which nullifies the positive zero and provides adaptive compensation to the moving poles of the boost and buck/boost converters. This allows a simple unified design procedure to be devised for selecting the key SCM control parameters for an arbitrarily given power stage configuration and parameter values, such that all regulator performance specifications can be met and optimized concurrently in a single design attempt.

  13. GaN HFET-Based DC/DC Converters for Low Power RF Satellite Equipment

    NASA Astrophysics Data System (ADS)

    Delamare, Guillaume; Maynadier, Paul; Schneider, Henri

    2014-08-01

    This paper presents the evaluation and prototyping of a low power, multiple outputs, isolated DC/DC converter for 100 V telecom satellite applications, using enhancement-mode GaN heterostructure field effect transistors (HFETs) to enable 1 MHz switching frequencies.Radiation-hardened power MOSFETs are currently the main drivers for both cost and size (because of their limited switching frequency) of existing DC/DC converters. Commercially available normally-off GaN HFETs are very promising replacements, thanks to their high switching speed and intrinsic radiation hardness.In this study different designs, built around various isolated topologies, were compared for a typical low power RF application (10W) with a switching frequency of 1 MHz. Calculations and simulations helped select the most adequate architecture in terms of size and efficiency. A prototype was then built and its performance measured. Electromagnetic compatibility was evaluated by mating the power supply to its RF equipment.

  14. A Switching-Mode Power Supply Design Tool to Improve Learning in a Power Electronics Course

    ERIC Educational Resources Information Center

    Miaja, P. F.; Lamar, D. G.; de Azpeitia, M.; Rodriguez, A.; Rodriguez, M.; Hernando, M. M.

    2011-01-01

    The static design of ac/dc and dc/dc switching-mode power supplies (SMPS) relies on a simple but repetitive process. Although specific spreadsheets, available in various computer-aided design (CAD) programs, are widely used, they are difficult to use in educational applications. In this paper, a graphic tool programmed in MATLAB is presented,…

  15. A Switching-Mode Power Supply Design Tool to Improve Learning in a Power Electronics Course

    ERIC Educational Resources Information Center

    Miaja, P. F.; Lamar, D. G.; de Azpeitia, M.; Rodriguez, A.; Rodriguez, M.; Hernando, M. M.

    2011-01-01

    The static design of ac/dc and dc/dc switching-mode power supplies (SMPS) relies on a simple but repetitive process. Although specific spreadsheets, available in various computer-aided design (CAD) programs, are widely used, they are difficult to use in educational applications. In this paper, a graphic tool programmed in MATLAB is presented,…

  16. Over Current Protection for PFM Control DC-DC Converter

    NASA Astrophysics Data System (ADS)

    Yamada, Kouhei; Sugahara, Satoshi; Fujii, Nobuo

    An over current protection method suitable for Fixed ON-time PFM (Pulse Frequency Modulation) Control DC-DC converters is proposed. It is based on inductor bottom current limiting, realized by monitoring the synchronous rectifier current and extending the OFF-phase of the main switch until it decreases to a predetermined limit, and can properly limit the output current even in case of short circuit. A Fixed ON-time PFM DC-DC converter with the proposed over current protection was designed and fabricated in CMOS IC. Its current limiting operation was verified with simulations and measurements.

  17. Experiences in the Application of Project-Based Learning in a Switching-Mode Power Supplies Course

    ERIC Educational Resources Information Center

    Lamar, D. G.; Miaja, P. F.; Arias, M.; Rodriguez, A.; Rodriguez, M.; Vazquez, A.; Hernando, M. M.; Sebastian, J.

    2012-01-01

    This paper presents the introduction of problem-based learning (PBL) in a power electronics course at the University of Oviedo, Gijon, Spain, by means of two practical projects: the design and construction of a switching-mode power supply (SMPS) prototype and the static study of a dc-dc converter topology. The goal of this innovation was for…

  18. New topology for DC/DC bidirectional converter for hybrid systems in renewable energy

    NASA Astrophysics Data System (ADS)

    Lopez, Juan Carlos; Ortega, Manuel; Jurado, Francisco

    2015-03-01

    This article presents a new isolated DC/DC bidirectional converter with soft switching, using a transformer with two voltage taps and two full bridges with insulated-gate bipolar transistors (IGBTs), one on each side of the transformer to be integrated in hybrid systems of renewable energy. A large voltage conversion ratio can be achieved using this converter, in buck and booster modes. Also medium and high DC power can be converted with a good efficiency. Analysis and switching techniques have been reported. To verify the principle of operation, a laboratory prototype of 10 kW has been performed. Experimental results are presented, operating in boost mode. The switching algorithm used has been modelled in MATLAB-Simulink to generate C code. This code has been implemented in a DSP F2812, which has been used to build the prototype.

  19. Power Network impedance effects on noise emission of DC-DC converters

    NASA Astrophysics Data System (ADS)

    Esteban, M. C.; Arteche, F.; Iglesias, M.; Gimeno, A.; Arcega, F. J.; Johnson, M.; Cooper, W. E.

    2012-01-01

    The characterization of electromagnetic noise emissions of DC-DC converters is a critical issue that has been analyzed during the desing phase of CMS tracker upgrade. Previous simulation studies showed important variations in the level of conducted emissions when DC-DC converters are loaded/driven by different impedances and power network topologies. Several tests have been performed on real DC-DC converters to validate the Pspice model and simulation results. This paper presents these test results. Conducted noise emissions at the input and at the output terminals of DC-DC converters has been measured for different types of power and FEE impedances. Special attention has been paid to influence on the common-mode emissions by the carbon fiber material used to build the mechanical structure of the central detector. These study results show important recommendations and criteria to be applied in order to decrease the system noise level when integrating the DC-DC.

  20. GaN Microwave DC-DC Converters

    NASA Astrophysics Data System (ADS)

    Ramos Franco, Ignacio

    Increasing the operating frequency of switching converters can have a direct impact in the miniaturization and integration of power converters. The size of energy-storage passive components and the difficulty to integrate them with the rest of the circuitry is a major challenge in the development of a fully integrated power supply on a chip. The work presented in this thesis attempts to address some of the difficulties encountered in the design of high-frequency converters by applying concepts and techniques usually used in the design of high-efficiency power amplifiers and high-efficiency rectifiers at microwave frequencies. The main focus is in the analysis, design, and characterization of dc-dc converters operating at microwave frequencies in the low gigahertz range. The concept of PA-rectifier duality, where a high-efficiency power amplifier operates as a high-efficiency rectifier is investigated through non-linear simulations and experimentally validated. Additionally, the concept of a self-synchronous rectifier, where a transistor rectifier operates synchronously without the need of a RF source or driver is demonstrated. A theoretical analysis of a class-E self-synchronous rectifier is presented and validated through non-linear simulations and experiments. Two GaN class-E2 dc-dc converters operating at a switching frequency of 1 and 1.2 GHz are demonstrated. The converters achieve 80 % and 75 % dc-dc efficiency respectively and are among the highest-frequency and highest-efficiency reported in the literature. The application of the concepts established in the analysis of a self-synchronous rectifier to a power amplifier culminated in the development of an oscillating, self-synchronous class-E 2 dc-dc converter. Finally, a proof-of-concept fully integrated GaN MMIC class-E 2 dc-dc converter switching at 4.6 GHz is demonstrated for the first time to the best of our knowledge. The 3.8 mm x 2.6 mm chip contains distributed inductors and does not require any

  1. Optimum Design of CMOS DC-DC Converter for Mobile Applications

    NASA Astrophysics Data System (ADS)

    Katayama, Yasushi; Edo, Masaharu; Denta, Toshio; Kawashima, Tetsuya; Ninomiya, Tamotsu

    In recent years, low output power CMOS DC-DC converters which integrate power stage MOSFETs and a PWM controller using CMOS process have been used in many mobile applications. In this paper, we propose the calculation method of CMOS DC-DC converter efficiency and report optimum design of CMOS DC-DC converter based on this method. By this method, converter efficiencies are directly calculated from converter specifications, dimensions of power stage MOSFET and device parameters. Therefore, this method can be used for optimization of CMOS DC-DC converter design, such as dimensions of power stage MOSFET and switching frequency. The efficiency calculated by the proposed method agrees well with the experimental results.

  2. DC/DC Converter Stability Testing Study

    NASA Technical Reports Server (NTRS)

    Wang, Bright L.

    2008-01-01

    This report presents study results on hybrid DC/DC converter stability testing methods. An input impedance measurement method and a gain/phase margin measurement method were evaluated to be effective to determine front-end oscillation and feedback loop oscillation. In particular, certain channel power levels of converter input noises have been found to have high degree correlation with the gain/phase margins. It becomes a potential new method to evaluate stability levels of all type of DC/DC converters by utilizing the spectral analysis on converter input noises.

  3. High gain high efficiency resonant DC-DC converter

    NASA Astrophysics Data System (ADS)

    Shang, Fei

    Low voltage power sources have played an important role in applications such as automotive system, renewable energy power generation and so on, where require a high gain DC-DC step-up converter. The converter is going to sustain a very high input current which can bring many design challenges in the existing topologies, such as high component current stress and power loss, complex and costly design for magnetic components, high input current ripple, etc. A new topology of high gain DCDC step-up converter proposed in this dissertation. The topology has many merits such as high gain capability, high efficiency, low components stress and requirement of the transformer, simple topology with less number of active switching devices, and easy to control. The dissertation carries out theoretical analysis of the proposed topology under different operating modes and the voltage gain has been deduced for each mode. The design of circuit components has been well studied, including the power devices current stress and power, the selection of transformer turns-ratio, the design method of the resonant tank and input current ripple. System dynamic state-space models are acquired by using generalized averaging method. Small signal model of the converter is achieved by linearization of the dynamic model around the operating points. The stability study indicates that the open loop system is stable at all operating points, except some operating points containing RHP zeros which can cause closed loop system unstable. The parameter sensitivity study shows that the system transfer function is not greatly affected by the variation of the leakage inductance and load resistance. A design of PI controller is implemented to achieve the output voltage regulation. Simulations have been carried out to validate the circuit operation and support the design analysis. A 2kW prototype has been built for experimental testing. The experimental results are in a good agreement with the theoretical

  4. Step-by-Step Design of an FPGA-Based Digital Compensator for DC/DC Converters Oriented to an Introductory Course

    ERIC Educational Resources Information Center

    Zumel, P.; Fernandez, C.; Sanz, M.; Lazaro, A.; Barrado, A.

    2011-01-01

    In this paper, a short introductory course to introduce field-programmable gate array (FPGA)-based digital control of dc/dc switching power converters is presented. Digital control based on specific hardware has been at the leading edge of low-medium power dc/dc switching converters in recent years. Besides industry's interest in this topic, from…

  5. Step-by-Step Design of an FPGA-Based Digital Compensator for DC/DC Converters Oriented to an Introductory Course

    ERIC Educational Resources Information Center

    Zumel, P.; Fernandez, C.; Sanz, M.; Lazaro, A.; Barrado, A.

    2011-01-01

    In this paper, a short introductory course to introduce field-programmable gate array (FPGA)-based digital control of dc/dc switching power converters is presented. Digital control based on specific hardware has been at the leading edge of low-medium power dc/dc switching converters in recent years. Besides industry's interest in this topic, from…

  6. Bi-Directional DC-DC Converter for PHEV Applications

    SciTech Connect

    Abas Goodarzi

    2011-01-31

    Plug-In Hybrid Electric Vehicles (PHEV) require high power density energy storage system (ESS) for hybrid operation and high energy density ESS for Electric Vehicle (EV) mode range. However, ESS technologies to maximize power density and energy density simultaneously are not commercially feasible. The use of bi-directional DC-DC converter allows use of multiple energy storage, and the flexible DC-link voltages can enhance the system efficiency and reduce component sizing. This will improve fuel consumption, increase the EV mode range, reduce the total weight, reduce battery initial and life cycle cost, and provide flexibility in system design.

  7. Performance evaluation of a high power DC-DC boost converter for PV applications using SiC power devices

    NASA Astrophysics Data System (ADS)

    Almasoudi, Fahad M.; Alatawi, Khaled S.; Matin, Mohammad

    2016-09-01

    The development of Wide band gap (WBG) power devices has been attracted by many commercial companies to be available in the market because of their enormous advantages over the traditional Si power devices. An example of WBG material is SiC, which offers a number of advantages over Si material. For example, SiC has the ability of blocking higher voltages, reducing switching and conduction losses and supports high switching frequency. Consequently, SiC power devices have become the affordable choice for high frequency and power application. The goal of this paper is to study the performance of 4.5 kW, 200 kHz, 600V DC-DC boost converter operating in continuous conduction mode (CCM) for PV applications. The switching behavior and turn on and turn off losses of different switching power devices such as SiC MOSFET, SiC normally ON JFET and Si MOSFET are investigated and analyzed. Moreover, a detailed comparison is provided to show the overall efficiency of the DC-DC boost converter with different switching power devices. It is found that the efficiency of SiC power switching devices are higher than the efficiency of Si-based switching devices due to low switching and conduction losses when operating at high frequencies. According to the result, the performance of SiC switching power devices dominate the conventional Si power devices in terms of low losses, high efficiency and high power density. Accordingly, SiC power switching devices are more appropriate for PV applications where a converter of smaller size with high efficiency, and cost effective is required.

  8. Two new families of high-gain dc-dc power electronic converters for dc-microgrids

    NASA Astrophysics Data System (ADS)

    Prabhala, Venkata Anand Kishore

    Distributing the electric power in dc form is an appealing solution in many applications such as telecommunications, data centers, commercial buildings, and microgrids. A high gain dc-dc power electronic converter can be used to individually link low-voltage elements such as solar panels, fuel cells, and batteries to the dc voltage bus which is usually 400 volts. This way, it is not required to put such elements in a series string to build up their voltages. Consequently, each element can function at it optimal operating point regardless of the other elements in the system. In this dissertation, first a comparative study of dc microgrid architectures and their advantages over their ac counterparts is presented. Voltage level selection of dc distribution systems is discussed from the cost, reliability, efficiency, and safety standpoints. Next, a new family of non-isolated high-voltage-gain dc-dc power electronic converters with unidirectional power flow is introduced. This family of converters benefits from a low voltage stress across its switches. The proposed topologies are versatile as they can be utilized as single-input or double-input power converters. In either case, they draw continuous currents from their sources. Lastly, a bidirectional high-voltage-gain dc-dc power electronic converter is proposed. This converter is comprised of a bidirectional boost converter which feeds a switched-capacitor architecture. The switched-capacitor stage suggested here has several advantages over the existing approaches. For example, it benefits from a higher voltage gain while it uses less number of capacitors. The proposed converters are highly efficient and modular. The operating modes, dc voltage gain, and design procedure for each converter are discussed in details. Hardware prototypes have been developed in the lab. The results obtained from the hardware agree with those of the simulation models.

  9. Modeling and analysis of fractional order DC-DC converter.

    PubMed

    Radwan, Ahmed G; Emira, Ahmed A; AbdelAty, Amr M; Azar, Ahmed Taher

    2017-07-11

    Due to the non-idealities of commercial inductors, the demand for a better model that accurately describe their dynamic response is elevated. So, the fractional order models of Buck, Boost and Buck-Boost DC-DC converters are presented in this paper. The detailed analysis is made for the two most common modes of converter operation: Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM). Closed form time domain expressions are derived for inductor currents, voltage gain, average current, conduction time and power efficiency where the effect of the fractional order inductor is found to be strongly present. For example, the peak inductor current at steady state increases with decreasing the inductor order. Advanced Design Systems (ADS) circuit simulations are used to verify the derived formulas, where the fractional order inductor is simulated using Valsa Constant Phase Element (CPE) approximation and Generalized Impedance Converter (GIC). Different simulation results are introduced with good matching to the theoretical formulas for the three DC-DC converter topologies under different fractional orders. A comprehensive comparison with the recently published literature is presented to show the advantages and disadvantages of each approach. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  10. DC-DC converter for discharging energy storage magnets

    NASA Astrophysics Data System (ADS)

    Eyssa, Yehia M.; Huang, Xianrui

    1994-07-01

    A new DC-DC converter to control the output power delivered from a magnetic energy storage magnet or an equivalent current source is discussed. The circuit consists of: (1) highly coupled transformer (air or iron core) with coupling coefficient better than 0.95; (2) low frequency mechanical or superconducting switches (0.1 - 10 Hz) or high frequency (10 - 1000 Hz) GTO switches depending on the application; and (3) small voltage source (capacitor or battery) to control the output voltage. Two examples illustrating the application of this circuit are discussed. They are a step up dc current converter for use in uninterruptible power supplies and a step down one for use in discharging large current storage coil into a small current load. The efficiency expected to exceed 90%.

  11. High power density dc/dc converter: Component selection and design

    NASA Technical Reports Server (NTRS)

    Divan, Deepakraj M.

    1989-01-01

    Further work pertaining to design considerations for the new high power, high frequency dc/dc converters is discussed. The goal of the project is the development of high power, high power density dc/dc converters at power levels in the multi-kilowatt to megawatt range for aerospace applications. The prototype converter is rated for 50 kW at a switching frequency of 50 kHz, with an input voltage of 200 Vdc and an output of 2000 Vdc. The overall power density must be in the vicinity of 0.2 to 0.3 kg/kW.

  12. Interleaved DC-DC Converter with Discrete Duty Cycle and Open Loop Control

    NASA Astrophysics Data System (ADS)

    Kroics, K.; Sokolovs, A.

    2016-08-01

    The authors present the control principle of the multiphase interleaved DC-DC converter that can be used to vastly reduce output current ripple of the converter. The control algorithm can be easily implemented by using microcontroller without current loop in each phase. The converter works in discontinuous conduction mode (DCM) but close to boundary conduction mode (BCM). The DC-DC converter with such a control algorithm is useful in applications that do not require precise current adjustment. The prototype of the converter has been built. The experimental results of the current ripple are presented in the paper.

  13. A 10 kW dc-dc converter using IGBTs with active snubbers. [Insulated Gate Bipolar Transistor

    NASA Technical Reports Server (NTRS)

    Masserant, Brian J.; Shriver, Jeffrey L.; Stuart, Thomas A.

    1993-01-01

    This full bridge dc-dc converter employs zero voltage switching (ZVS) on one leg and zero current switching (ZCS) on the other. This technique produces exceptionally low IGBT switching losses through the use of an active snubber that recycles energy back to the source. Experimental results are presented for a 10 kW, 20 kHz converter.

  14. Introduction of a current waveform, waveshaping technique to limit conduction loss in high-frequency dc-dc converters suitable for space power

    NASA Astrophysics Data System (ADS)

    Miller, Douglas P.

    1990-06-01

    Space power supply manufacturers have tried to increase power density and construct smaller, highly efficient power supplies by increasing switching frequency. Incorporation of a power MOSFET as a switching element alleviates switching loss. However, values of R sub DS(on) (drain-to-source resistance in the on-state) for MOSFET's are of such magnitude to produce greater on-state losses than an equivalent BJT operated in saturation. This research serves to introduce a design concept, pertinent to low-voltage relatively-high-current applications, that minimizes the peak current through the switching element in order to reduce average power loss. Basic waveforms produced by different PWM and resonant mode topologies were examined. Theoretical analysis reveals that a ramp-sine current waveform could cut conduction power loss by at least 18 percent over a conventional Buck switching converter. A 14V, 14W combination quasi-resonant Buck/ZCS, Quasi-Resonant Buck dc-dc converter with an unregulated input voltage of 28 V was built for simplicity to demonstrate one particular waveshaping technique. This converter represents a useful example of an actual circuit which is capable of producing the desired ramp-sine switch-current waveform. Final results confirm improvement in conduction loss enhancing existing power MOSFET technology for use in dc-dc power conversion.

  15. A high-power switch-mode dc power supply for dynamic loads

    SciTech Connect

    Shimer, D.W.; Lange, A.C.; Bombay, J.N.

    1994-06-23

    High-voltage dc power supplies are often required to operate with highly dynamic loads, such as arcs. A switch-mode dc power supply can offer significant advantages over conventional thyristor-based dc power supplies under such conditions. It can quickly turn off the supply to extinguish the arc, and it can quickly recover after the arc. It has a relatively small output filter capacitance, which results in small stored energy available to the arc. A 400-kW, 50-kV switch-mode dc power supply for an electron-beam gun that exploits these advantages was designed and tested. It uses four 100-kW, current-source-type dc-dc converters with inputs in parallel and outputs in series. The dc-dc converters operate at 20 kHz in the voltage regulator part and 10 kHz in the inverter, transformer, and output rectifier part of the circuit. Insulated gate bipolar transistors (IGBTs) are used as the power switches. Special techniques are used to protect the power supply and load against arcs and hard shorts. The power supply has an efficiency of 93%, an output voltage ripple of 1%, and fast dynamic response. In addition, it is nearly one-third the size of conventional power supplies.

  16. Radiation-Tolerant DC-DC Converters

    NASA Technical Reports Server (NTRS)

    Skutt, Glenn; Sable, Dan; Leslie, Leonard; Graham, Shawn

    2012-01-01

    A document discusses power converters suitable for space use that meet the DSCC MIL-PRF-38534 Appendix G radiation hardness level P classification. A method for qualifying commercially produced electronic parts for DC-DC converters per the Defense Supply Center Columbus (DSCC) radiation hardened assurance requirements was developed. Development and compliance testing of standard hybrid converters suitable for space use were completed for missions with total dose radiation requirements of up to 30 kRad. This innovation provides the same overall performance as standard hybrid converters, but includes assurance of radiation- tolerant design through components and design compliance testing. This availability of design-certified radiation-tolerant converters can significantly reduce total cost and delivery time for power converters for space applications that fit the appropriate DSCC classification (30 kRad).

  17. Intelligent dc-dc Converter Technology Developed and Tested

    NASA Technical Reports Server (NTRS)

    Button, Robert M.

    2001-01-01

    The NASA Glenn Research Center and the Cleveland State University have developed a digitally controlled dc-dc converter to research the benefits of flexible, digital control on power electronics and systems. Initial research and testing has shown that conventional dc-dc converters can benefit from improved performance by using digital-signal processors and nonlinear control algorithms.

  18. Model predictive control of bidirectional isolated DC-DC converter for energy conversion system

    NASA Astrophysics Data System (ADS)

    Akter, Parvez; Uddin, Muslem; Mekhilef, Saad; Tan, Nadia Mei Lin; Akagi, Hirofumi

    2015-08-01

    Model predictive control (MPC) is a powerful and emerging control algorithm in the field of power converters and energy conversion systems. This paper proposes a model predictive algorithm to control the power flow between the high-voltage and low-voltage DC buses of a bidirectional isolated full-bridge DC-DC converter. The predictive control algorithm utilises the discrete nature of the power converters and predicts the future nature of the system, which are compared with the references to calculate the cost function. The switching state that minimises the cost function is selected for firing the converter in the next sampling time period. The proposed MPC bidirectional DC-DC converter is simulated with MATLAB/Simulink and further verified with a 2.5 kW experimental configuration. Both the simulation and experimental results confirm that the proposed MPC algorithm of the DC-DC converter reduces reactive power by avoiding the phase shift between primary and secondary sides of the high-frequency transformer and allow power transfer with unity power factor. Finally, an efficiency comparison is performed between the MPC and dual-phase-shift-based pulse-width modulation controlled DC-DC converter which ensures the effectiveness of the MPC controller.

  19. A Nonlinear Digital Control Solution for a DC/DC Power Converter

    NASA Technical Reports Server (NTRS)

    Zhu, Minshao

    2002-01-01

    A digital Nonlinear Proportional-Integral-Derivative (NPID) control algorithm was proposed to control a 1-kW, PWM, DC/DC, switching power converter. The NPID methodology is introduced and a practical hardware control solution is obtained. The design of the controller was completed using Matlab (trademark) Simulink, while the hardware-in-the-loop testing was performed using both the dSPACE (trademark) rapid prototyping system, and a stand-alone Texas Instruments (trademark) Digital Signal Processor (DSP)-based system. The final Nonlinear digital control algorithm was implemented and tested using the ED408043-1 Westinghouse DC-DC switching power converter. The NPID test results are discussed and compared to the results of a standard Proportional-Integral (PI) controller.

  20. A Nonlinear Digital Control Solution for a DC/DC Power Converter

    NASA Astrophysics Data System (ADS)

    Zhu, Minshao

    2002-02-01

    A digital Nonlinear Proportional-Integral-Derivative (NPID) control algorithm was proposed to control a 1-kW, PWM, DC/DC, switching power converter. The NPID methodology is introduced and a practical hardware control solution is obtained. The design of the controller was completed using Matlab (trademark) Simulink, while the hardware-in-the-loop testing was performed using both the dSPACE (trademark) rapid prototyping system, and a stand-alone Texas Instruments (trademark) Digital Signal Processor (DSP)-based system. The final Nonlinear digital control algorithm was implemented and tested using the ED408043-1 Westinghouse DC-DC switching power converter. The NPID test results are discussed and compared to the results of a standard Proportional-Integral (PI) controller.

  1. Interleaved Flyback DC-DC Converter Design with 350 W Power Output Using LT 3757 in LT Spice

    NASA Astrophysics Data System (ADS)

    Rahayu, S.; Firmansyah, E.; Isnaeni, M.

    2017-04-01

    DC-DC converter becomes one important part in micro-inverter used in solar panel application. Its function is to convert output voltage level of solar panel 42-48 Vdc to a voltage level of 350 Vdc before being converted into an AC voltage at the inverter. The proposed converter topology is a flyback because the number of components used is not too much which can suppress the production cost. In this paper, simulation of flyback converter on the interleaved operating mode with a maximum output power of 350 W using software Ltspicewas conducted. From the simulation results, obtained that by applying a switching frequency of 100 kHz, the obtained value of the components of the primary inductor (LP) 3.3 μH, the secondary inductor (LS) 27 μH, the output capacitor (Cout) 47μF and ripple voltage (Vr) 212.65 mV.

  2. Efficiency and weight of voltage multiplier type ultra lightweight dc-dc converters

    NASA Technical Reports Server (NTRS)

    Harrigill, W. T., Jr.; Myers, I. T.

    1975-01-01

    An analytical and experimental study was made of a capacitor-diode voltage multiplier without a transformer which offers the possibility of high efficiency with light weight. The dc-dc conversion efficiencies of about 94 percent were achieved at output powers of 150 watts at 1000 volts using 8x multiplication. A detailed identification of losses was made, including forward drop losses in component, switching losses, reverse junction capacitance charging losses, and charging losses in the main ladder capacitors.

  3. Design of a Multiple-Input SC DC-DC Converter Realizing Long Battery Runtime

    NASA Astrophysics Data System (ADS)

    Eguchi, Kei; Pongswatd, Sawai; Julsereewong, Amphawan; Tirasesth, Kitti; Sasaki, Hirofumi; Inoue, Takahiro

    A multiple-input switched-capacitor DC-DC converter which can realize long battery runtime is proposed in this letter. Unlike conventional converters for a back-lighting application, the proposed converter drives some LEDs by converting energy from solar cells. Furthermore, the proposed converter can charge a lithium battery when an output load is light. The validity of circuit design is confirmed by theoretical analyses, simulations, and experiments.

  4. Bifurcation Analysis of a DC-DC Bidirectional Power Converter Operating with Constant Power Loads

    NASA Astrophysics Data System (ADS)

    Cristiano, Rony; Pagano, Daniel J.; Benadero, Luis; Ponce, Enrique

    Direct current (DC) microgrids (MGs) are an emergent option to satisfy new demands for power quality and integration of renewable resources in electrical distribution systems. This work addresses the large-signal stability analysis of a DC-DC bidirectional converter (DBC) connected to a storage device in an islanding MG. This converter is responsible for controlling the balance of power (load demand and generation) under constant power loads (CPLs). In order to control the DC bus voltage through a DBC, we propose a robust sliding mode control (SMC) based on a washout filter. Dynamical systems techniques are exploited to assess the quality of this switching control strategy. In this sense, a bifurcation analysis is performed to study the nonlinear stability of a reduced model of this system. The appearance of different bifurcations when load parameters and control gains are changed is studied in detail. In the specific case of Teixeira Singularity (TS) bifurcation, some experimental results are provided, confirming the mathematical predictions. Both a deeper insight in the dynamic behavior of the controlled system and valuable design criteria are obtained.

  5. A High Voltage Ratio and Low Ripple Interleaved DC-DC Converter for Fuel Cell Applications

    PubMed Central

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

    2012-01-01

    This paper proposes a high voltage ratio and low ripple interleaved boost DC-DC converter, which can be used to reduce the output voltage ripple. This converter transfers the low DC voltage of fuel cell to high DC voltage in DC link. The structure of the converter is parallel with two voltage-doubler boost converters by interleaving their output voltages to reduce the voltage ripple ratio. Besides, it can lower the current stress for the switches and inductors in the system. First, the PSIM software was used to establish a proton exchange membrane fuel cell and a converter circuit model. The simulated and measured results of the fuel cell output characteristic curve are made to verify the correctness of the established simulation model. In addition, some experimental results are made to validate the effectiveness in improving output voltage ripple of the proposed high voltage ratio interleaved boost DC-DC converters. PMID:23365536

  6. SUBCONTRACT REPORT: DC-DC Converter for Fuel Cell and Hybrid Vehicles

    SciTech Connect

    Marlino, Laura D; Zhu, Lizhi

    2007-07-01

    The goal of this project is to develop and fabricate a 5kW dc-dc converter with a baseline 14V output capability for fuel cell and hybrid vehicles. The major objectives for this dc-dc converter technology are to meet: Higher efficiency (92%); High coolant temperature,e capability (105 C); High reliability (15 Years/150,000miles); Smaller volume (5L); Lower weight (6kg); and Lower cost ($75/kW). The key technical challenge for these converters is the 105 C coolant temperatures. The power switches and magnetics must be designed to sustain these operating temperatures reliably, without a large cost/mass/volume penalty.

  7. Silicon carbide DC-DC multilevel Cuk converter

    NASA Astrophysics Data System (ADS)

    Almalaq, Yasser; Alateeq, Ayoob; Matin, Mohammad

    2016-09-01

    In this paper, DC-DC multilevel cuk converter using silicon carbide (SiC) Components is presented. Cuk converter gives output voltage with negative polarity. This topology is useful for applications require high gain with limitation on duty cycle. The gain of the design can be enhanced by increasing the number of multiplier level (N). This relation between the gain and the number of levels is the major advantage of this multilevel cuk converter. In the proposed cuk converter, a single SiC MOSFET, 2N-1 SiC schottky diodes, 2N capacitors, 2 inductors, and single input voltage are used to supply a load with negative polarity. 300V input voltage, 50KHz switching frequency, and 75% duty cycle are the main parameters used in the design. The output parameters are 3KW power and -5.7 KV voltage. Because this design can be used in applications which temperature plays a critical role, the relation between increasing temperature and output voltage and power are tested. The design is simulated using LTspice software and the results are discussed.

  8. Early Oscillation Detection for DC/DC Converter Fault Diagnosis

    NASA Technical Reports Server (NTRS)

    Wang, Bright L.

    2011-01-01

    The electrical power system of a spacecraft plays a very critical role for space mission success. Such a modern power system may contain numerous hybrid DC/DC converters both inside the power system electronics (PSE) units and onboard most of the flight electronics modules. One of the faulty conditions for DC/DC converter that poses serious threats to mission safety is the random occurrence of oscillation related to inherent instability characteristics of the DC/DC converters and design deficiency of the power systems. To ensure the highest reliability of the power system, oscillations in any form shall be promptly detected during part level testing, system integration tests, flight health monitoring, and on-board fault diagnosis. The popular gain/phase margin analysis method is capable of predicting stability levels of DC/DC converters, but it is limited only to verification of designs and to part-level testing on some of the models. This method has to inject noise signals into the control loop circuitry as required, thus, interrupts the DC/DC converter's normal operation and increases risks of degrading and damaging the flight unit. A novel technique to detect oscillations at early stage for flight hybrid DC/DC converters was developed.

  9. ASIC and FPGA based DPWM architectures for single-phase and single-output DC-DC converter: a review

    NASA Astrophysics Data System (ADS)

    Chander, Subhash; Agarwal, Pramod; Gupta, Indra

    2013-12-01

    Pulse width modulation (PWM) has been widely used in power converter control. This paper presents a review of architectures of the Digital Pulse Width Modulators (DPWM) targeting digital control of switching DC-DC converters. An attempt is made to review the reported architectures with emphasis on the ASIC and FPGA implementations in single phase and single-output DC-DC converters. Recent architectures using FPGA's advanced resources for achieving the resolution higher than classical methods have also been discussed. The merits and demerits of different architectures, and their relative comparative performance, are also presented. The Authors intention is to uncover the groundwork and the related references through this review for the benefit of readers and researchers targeting different DPWM architectures for the DC-DC converters.

  10. Isolated Bidirectional DC-DC Converter for Hybrid Electric Vehicle Application

    DTIC Science & Technology

    2006-06-13

    34Approved for public release: distribution is unlimited" Isolated Bidirectional DC-DC Converter for Hybrid Electric Vehicle Applications Sonya...requirements for DC-DC converters for electric and hybrid vehicles . This paper introduces a bidirectional, isolated DC-DC converter for medium power...the design and build of a medium power DC-DC converter . Key words: Power Converter , DC-DC, Hybrid Electric Vehicle , Battery, Galvanically Isolation

  11. First experimental results from DC/DC and AC/DC plasma-based power transformers

    NASA Astrophysics Data System (ADS)

    McEvoy, Aaron; Gibson, William; Nebel, Richard

    2016-10-01

    A plasma-based power transformer has been built and operated in both DC/DC and AC/DC mode. The proprietary Tibbar Plasma Technologies, Inc. transformer design consists of two cylindrically symmetric helical primary electrodes surrounding a low temperature plasma within which a secondary axial current is generated. Initial experimental results have compared well with simulations and moderate conversion efficiencies have been observed. A new proprietary device is currently being constructed that will utilize 3-phase 480 VAC input to achieve higher conversion efficiency and output power. A description of the apparatus and several potential applications will be presented along with preliminary experimental data demonstrating the DC/DC and AC/DC conversion processes. Work performed under ARPA-E contract DE-AR0000677.

  12. Research of digital controlled DC/DC converter based on STC12C5410AD

    NASA Astrophysics Data System (ADS)

    Chen, Dan-Jiang; Jin, Xin; Xiao, Zhi-Hong

    2010-02-01

    In order to study application of digital control technology on DC/DC converter, principle of increment mode PID control algorithm was analyzed in the paper. Then, a SCM named STC12C5410AD was introduced with its internal resources and characteristics. The PID control algorithm can be implemented easily based on it. The output of PID control was used to change the value of a variable that is 255 times than duty cycle, and this reduced the error of calculation. The valid of the presented algorithm was verified by an experiment for a BUCK DC/DC converter. The experimental results indicated that output voltage of the BUCK converter is stable with low ripple.

  13. Bidirectional DC-DC Converter for Supercapacitor-Linked Power Interface in Advanced Electric Vehicles

    NASA Astrophysics Data System (ADS)

    Mishima, Tomokazu; Hiraki, Eiji; Yamamoto, Kouji; Tanaka, Toshihiko

    A bidirectional DC-DC converter for supercapacitor-based energy storage systems in advanced electric vehicles is proposed in this letter. This converter consists of a half-bridge and current-fed push-pull circuit linked with a high frequency transformer, which is well applicable to the low voltage/high current charge and discharge of the supercapacitor. The experimental results of the prototype system prove the effective properties of the proposed topology in terms of a low device-conduction loss and a low switching surge.

  14. Research on transient hysteresis current control strategy of DC-DC converter

    NASA Astrophysics Data System (ADS)

    Zhang, Ting; Wang, Zu-liang; Zhao, Yu-kai

    2017-01-01

    In order to improve the dynamic performance of DC-DC converter, transient hysteresis current control strategy is proposed which is based on parallel computing and combinational logic. By making a comparison between the real-time inductor current and the threshold inductor current, the switch is controlled more accurately. Under the Matlab/Simulink environment, the process of the Buck-Boost converter was simulated. The simulation results show that the transient hysteresis current control strategy can effectively overcome the disadvantages when load changes or input voltage disturbance occurs, it posses high load regulation and short dynamic response time, and it verifies the feasibility of the proposed strategy.

  15. A single-inductor dual-output switching converter with average current mode control

    NASA Astrophysics Data System (ADS)

    Weiwei, Xu; Xiaoting, Zhu; Zhiliang, Hong; D, Killat

    2009-09-01

    An integrated single-inductor dual-output (SIDO) switching DC-DC converter is presented. The outputs are specified with 1.2 V/400 mA and 1.8 V/200 mA. A decoupling small signal model is proposed to analyze the multi-loop system and to design the on-chip compensators. An average current control mode is introduced with lossless, continuous current detection. The converter has been fabricated in a 0.25 μm 2P4M CMOS process. The power efficiency is 86% at a total output power of 840 mW while the output ripples are about 40 mV at an oscillator frequency of 600 kHz.

  16. Universal and inductorless DC/DC converter for multi-output power supplies in sensor and actuator networks

    NASA Astrophysics Data System (ADS)

    Saponara, Sergio; Ciarpi, Gabriele

    2017-05-01

    This work proposes a universal and inductorless DC/DC converter that can be used for a wide input range, from few V to 60 V, to regulate output voltages from 5 V down to 1 V in Sensor and Actuator Network nodes. The proposed converter has been developed within the Athenis3D European project. It is composed by a cascade of multiple switching capacitor stages, with a proper skip-mode control to implement both step-down and step-up converting ratios, thus regulating all input sources to a voltage of about 6 V. These switching stages are further cascaded with linear regulators, which can provide stable output voltages down to 1 V. The multi-output regulator has been realized as a single-chip in a low-cost 0.35 μm CMOS technology. It is available as a naked die or in a ceramic package. The only needed external components are surface mount capacitors, which can be integrated on top of the naked chip die, creating a 3D structure, using trench capacitors embedded in a passive interposing layer. This way the size of the power management unit is further minimized. An advantage of the proposed converter is that it isn't optimized for a particular input voltage, therefore it can be used with no constant input power, like power harvesting systems (e.g. solar cells, wind and water turbines) and very disturbed power supplies.

  17. A 1.6-kW, 110-kHz dc-dc converter optimized for IGBT's

    NASA Technical Reports Server (NTRS)

    Chen, Keming; Stuart, Thomas A.

    1993-01-01

    A full bridge dc-dc converter using a zero-current and zero-voltage switching technique is described. This circuit utilizes the characteristics of the IGBT to achieve power and frequency combinations that are much higher than previously reported for this device. Experimental results are included for a 1.6-kW, 110-kHz converter with 95 percent efficiency.

  18. Digital Control Technologies for Modular DC-DC Converters

    NASA Technical Reports Server (NTRS)

    Button, Robert M.; Kascak, Peter E.; Lebron-Velilla, Ramon

    2002-01-01

    Recent trends in aerospace Power Management and Distribution (PMAD) systems focus on using commercial off-the-shelf (COTS) components as standard building blocks. This move to more modular designs has been driven by a desire to reduce costs and development times, but is also due to the impressive power density and efficiency numbers achieved by today's commercial DC-DC converters. However, the PMAD designer quickly learns of the hidden "costs" of using COTS converters. The most significant cost is the required addition of external input filters to meet strict electromagnetic interference (MIAMI) requirements for space systems. In fact, the high power density numbers achieved by the commercial manufacturers are greatly due to the lack of necessary input filters included in the COTS module. The NASA Glenn Research Center is currently pursuing a digital control technology that addresses this problem with modular DC-DC converters. This paper presents the digital control technologies that have been developed to greatly reduce the input filter requirements for paralleled, modular DC-DC converters. Initial test result show that the input filter's inductor size was reduced by 75 percent, and the capacitor size was reduced by 94 percent while maintaining the same power quality specifications.

  19. Static and Dynamic Characteristics of DC-DC Converter Using a Digital Filter

    NASA Astrophysics Data System (ADS)

    Kurokawa, Fujio; Okamatsu, Masashi

    This paper presents the regulation and dynamic characteristics of the dc-dc converter with digital PID control, the minimum phase FIR filter or the IIR filter, and then the design criterion to improve the dynamic characteristics is discussed. As a result, it is clarified that the DC-DC converter using the IIR filter method has superior performance characteristics. The regulation range is within 1.3%, the undershoot against the step change of the load is less than 2% and the transient time is less than 0.4ms with the IIR filter method. In this case, the switching frequency is 100kHz and the step change of the load R is from 50 Ω to 10 Ω. Further, the superior characteristics are obtained when the first gain, the second gain and the second cut-off frequency are relatively large, and the first cut-off frequency and the passing frequency are relatively low. Moreover, it is important that the gain strongly decreases at the second cut-off frequency because the upper band pass frequency range must be always less than half of the sampling frequency based on the sampling theory.

  20. Light weight, high power, high voltage dc/dc converter technologies

    NASA Technical Reports Server (NTRS)

    Kraus, Robert; Myers, Ira; Baumann, Eric

    1990-01-01

    Power-conditioning weight reductions by orders of magnitude will be required to enable the megawatt-power-level space systems envisioned by the Strategic Defense Initiative, the Air Force, and NASA. An interagency program has been initiated to develop an 0.1-kg/kW dc/dc converter technology base for these future space applications. Three contractors are in the first phase of a competitive program to develop a megawatt dc/dc converter. Researchers at NASA Lewis Research Center are investigating innovative converter topology control. Three different converter subsystems based on square wave, resonant, and super-resonant topologies are being designed. The components required for the converter designs cover a wide array of technologies. Two different switches, one semiconductor and the other gas, are under development. Issues related to thermal management and material reliability for inductors, transformers, and capacitors are being investigated in order to maximize power density. A brief description of each of the concepts proposed to meet the goals of this program is presented.

  1. Light weight, high power, high voltage dc/dc converter technologies

    NASA Technical Reports Server (NTRS)

    Kraus, Robert; Myers, Ira; Baumann, Eric

    1990-01-01

    Power-conditioning weight reductions by orders of magnitude will be required to enable the megawatt-power-level space systems envisioned by the Strategic Defense Initiative, the Air Force, and NASA. An interagency program has been initiated to develop an 0.1-kg/kW dc/dc converter technology base for these future space applications. Three contractors are in the first phase of a competitive program to develop a megawatt dc/dc converter. Researchers at NASA Lewis Research Center are investigating innovative converter topology control. Three different converter subsystems based on square wave, resonant, and super-resonant topologies are being designed. The components required for the converter designs cover a wide array of technologies. Two different switches, one semiconductor and the other gas, are under development. Issues related to thermal management and material reliability for inductors, transformers, and capacitors are being investigated in order to maximize power density. A brief description of each of the concepts proposed to meet the goals of this program is presented.

  2. Commercial Of-The Shelf DC/DC Converter

    NASA Astrophysics Data System (ADS)

    Denzinger, W.; Baumel, S.

    2011-10-01

    A commercial of-the-shelf (COTS) DC/DC converter for the supply of digital electronics on board of spacecraft has been developed with special emphasis on: *Low cost Readily available *Easy manufacturing *No use of ITAR listed EEE parts like rad-hard mosfets *Minimum number of rad-hard digital and analog IC's *Design tolerance against SEE by appropriate filtering The study was supported by the European Space Agency (ESA) under the contract number 21729/08/NL7LvH.

  3. Low dose failures of hardened DC-DC power converters

    NASA Technical Reports Server (NTRS)

    Lehman, J.; Yui, C.; Rax, B. G.; Miyahira, T. F.; Weideman, M.; Schrick, P.; Swift, G. M.; Johnston, A. H.

    2002-01-01

    Box-level total dose testing of the FOG (Fiber Optic Gyro) by IXSEA at ESA's GammabeamFacility were abruptly terminated at 8krad (Si) due to catastrophic failure (complete shutdown). This was unexpected because all components within the gyro were supposedly radiation tolerant. Further testing showed that the components responsible for the failure were two DC-DC converters, manufactured by Interpoint, that stopped regulating shortly before shutdown. This paper summarizes diagnostic test results for the converters to determine the underlying cause of the unexpected failure at low levels of radiation.

  4. High efficiency interleaved bi-directional ZVS DC-DC converter

    NASA Astrophysics Data System (ADS)

    Zafarullah Khan, M.; Mohsin Naveed, M.; Akbar Hussain, D. M.

    2013-06-01

    A high efficiency interleaved bi-directional ZVS DC-DC converter is presented in this paper. This converter can be operated in both buck and boost mode. CoolMOS is used as a power device to achieve low conduction losses and fast turn off. The value of inductance is selected such that the CoolMOS drain-to-source voltage always falls to zero before it turns on and ZVS is achieved. Multiphase interleaved inductors are used to achieve high power and low ripple currents. Converter is operated at 50kHz and MATLAB Simulink simulation is performed. 6kW prototype converter is implemented in buck mode and simulation results are verified.

  5. Load adaptive start-up scheme for synchronous boost DC-DC converter

    NASA Astrophysics Data System (ADS)

    Guoding, Dai; Wenliang, Xiu; Yuezhi, Liu; Yawei, Qi; Zuqi, Dong

    2016-10-01

    This paper presents a load adaptive soft-start scheme through which the inductor current of the synchronous boost DC-DC converter can trace the load current at the start-up stage. This scheme effectively eliminates the inrush-current and over-shoot voltage and improves the load capability of the converter. According to the output voltage, the start-up process is divided into three phases and at each phase the inductor current is limited to match the load. In the pre-charge phase, a step-increasing constant current gives a smooth rise of the output voltage which avoids inrush current and ensures the converter successfully starts up at different load situations. An additional ring oscillator operation phase enables the converter to start up as low as 1.4 V. When the converter enters into the system loop soft-start phase, an output voltage and inductor current detection methods make the transition of the phases smooth and the inductor current and output voltage rise steadily. Effective protection circuits such as short-circuit protection, current limit circuit and over-temperature protection circuit are designed to guarantee the safety and reliability of the chip during the start-up process. The proposed start-up circuit is implemented in a synchronous boost DC-DC converter based on TSMC 0.35 μm CMOS process with an input voltage range 1.4-4.2 V, and a steady output voltage 5 V, and the switching frequency is 1 MHz. Simulation results show that inrush current and overshoot voltage are suppressed with a load range from 0-2.1 A, and inductor current is as low as 259 mA when the output shorts to the ground.

  6. A novel standby mode detection scheme with light load efficiency improvement

    NASA Astrophysics Data System (ADS)

    Hu, Jiajun; Chen, Houpeng; Wang, Qian; Li, Xi; Fan, Xi; Miao, Jie; Song, Zhitang

    2016-10-01

    A novel standby mode scheme with light load efficiency improvement is proposed in this paper, which is especially suitable for modern boost dc-dc converters powered by Li-ion battery. The proposed output load estimator is able to accurately reflect the output load current under light load condition once inductor current enters in the discontinuous conduction mode (DCM). Our experimental results show that the proposed boost dc-dc converter can automatically select approximate PWM switching frequency according to the detected information of the proposed output load estimator, regardless of power supply and inductor value.

  7. Advanced DC/DC Converters towards higher Volumetric Efficiencies for Space Applications

    NASA Technical Reports Server (NTRS)

    Plante, Jeannette; Shue, Jack; Liu, David; Wang, Bright; Shaw, Harry

    2005-01-01

    Contents include the following: 1. NASA mission outlook. 2. Issues with DC/DC converter for space. 3. Statement of newly initiated engineering activities for DC/DC converter. 4. Overview of prototyping work with novel materials. 5. Results of cryogenic testing.

  8. Analysis and Design of Bridgeless Switched Mode Power Supply for Computers

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  9. Path planning during combustion mode switch

    DOEpatents

    Jiang, Li; Ravi, Nikhil

    2015-12-29

    Systems and methods are provided for transitioning between a first combustion mode and a second combustion mode in an internal combustion engine. A current operating point of the engine is identified and a target operating point for the internal combustion engine in the second combustion mode is also determined. A predefined optimized transition operating point is selected from memory. While operating in the first combustion mode, one or more engine actuator settings are adjusted to cause the operating point of the internal combustion engine to approach the selected optimized transition operating point. When the engine is operating at the selected optimized transition operating point, the combustion mode is switched from the first combustion mode to the second combustion mode. While operating in the second combustion mode, one or more engine actuator settings are adjusted to cause the operating point of the internal combustion to approach the target operating point.

  10. 76 FR 55109 - In the Matter of Certain DC-DC Controllers and Products Containing Same; Notice of Institution of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-06

    ... COMMISSION In the Matter of Certain DC-DC Controllers and Products Containing Same; Notice of Institution of... importation, and the sale within the United States after importation of certain DC-DC controllers and products... sale, and selling for importation DC-DC controllers, or products containing the same, into the United...

  11. Discrete time domain modelling and analysis of dc-dc converters with continuous and discontinuous inductor current

    NASA Technical Reports Server (NTRS)

    Iwens, R. P.; Lee, F. C.; Triner, J. E.

    1977-01-01

    Using discrete time state variable representation, a generalized computer-aided modeling and analysis of dc-dc converters is presented. The methodology provides exact modeling and is applicable to all types of power stages and duty-cycle control, including continuous and discontinuous inductor current operation. Converter stability, transient behavior and audio susceptibility can be analytically evaluated and predicted. The generalized theory of the proposed approach to converter modeling and analysis is presented first, followed by a demonstrative example applying the theory to a constant frequency buck converter operating in continuous and discontinuous inductor current mode. Excellent agreement with laboratory test data has been observed.

  12. Power Strategy in DC/DC Converters to Increase Efficiency of Electrical Stimulators.

    PubMed

    Aqueveque, Pablo; Acuña, Vicente; Saavedra, Francisco; Debelle, Adrien; Lonys, Laurent; Julémont, Nicolas; Huberland, François; Godfraind, Carmen; Nonclercq, Antoine

    2016-06-13

    Power efficiency is critical for electrical stimulators. Battery life of wearable stimulators and wireless power transmission in implanted systems are common limiting factors. Boost DC/DC converters are typically needed to increase the supply voltage of the output stage. Traditionally, boost DC/DC converters are used with fast control to regulate the supply voltage of the output. However, since stimulators are acting as current sources, such voltage regulation is not needed. Banking on this, this paper presents a DC/DC conversion strategy aiming to increase power efficiency. It compares, in terms of efficiency, the traditional use of boost converters to two alternatives that could be implemented in future hardware designs.

  13. Recovery Act: Integrated DC-DC Conversion for Energy-Efficient Multicore Processors

    SciTech Connect

    Shepard, Kenneth L

    2013-03-31

    In this project, we have developed the use of thin-film magnetic materials to improve in energy efficiency of digital computing applications by enabling integrated dc-dc power conversion and management with on-chip power inductors. Integrated voltage regulators also enables fine-grained power management, by providing dynamic scaling of the supply voltage in concert with the clock frequency of synchronous logic to throttle power consumption at periods of low computational demand. The voltage converter generates lower output voltages during periods of low computational performance requirements and higher output voltages during periods of high computational performance requirements. Implementation of integrated power conversion requires high-capacity energy storage devices, which are generally not available in traditional semiconductor processes. We achieve this with integration of thin-film magnetic materials into a conventional complementary metal-oxide-semiconductor (CMOS) process for high-quality on-chip power inductors. This project includes a body of work conducted to develop integrated switch-mode voltage regulators with thin-film magnetic power inductors. Soft-magnetic materials and inductor topologies are selected and optimized, with intent to maximize efficiency and current density of the integrated regulators. A custom integrated circuit (IC) is designed and fabricated in 45-nm CMOS silicon-on-insulator (SOI) to provide the control system and power-train necessary to drive the power inductors, in addition to providing a digital load for the converter. A silicon interposer is designed and fabricated in collaboration with IBM Research to integrate custom power inductors by chip stacking with the 45-nm CMOS integrated circuit, enabling power conversion with current density greater than 10A/mm2. The concepts and designs developed from this work enable significant improvements in performance-per-watt of future microprocessors in servers, desktops, and mobile

  14. Achievement of Bevalac rapid mode switching

    SciTech Connect

    Lothrop, F.; Stevenson, R.; Miller, R.; Alonso, J.

    1985-05-01

    Rapid changes of ion, intensity, beam line, and output energy between two modes have been achieved. The techniques for switching among the Bevalac's several injectors are described. Energy level limits at the output (for q/A = 1/2) are 470 to 2100 MeV/n (high power) or 50 to 1050 MeV/n (low power). Depending on specific field value differences, the total time required for a mode change is less than one minute. This mode of operation greatly improves program efficiency in interleaving medical and nuclear science programs at the Bevalac.

  15. Development of a DC-DC conversion powering scheme for the CMS Phase-1 pixel upgrade

    NASA Astrophysics Data System (ADS)

    Feld, L.; Fimmers, C.; Karpinski, W.; Klein, K.; Lipinski, M.; Preuten, M.; Rauch, M.; Rittich, D.; Sammet, J.; Wlochal, M.

    2014-01-01

    A novel powering scheme based on the DC-DC conversion technique will be exploited to power the CMS Phase-1 pixel detector. DC-DC buck converters for the CMS pixel project have been developed, based on the AMIS5 ASIC designed by CERN. The powering system of the Phase-1 pixel detector is described and the performance of the converter prototypes is detailed, including power efficiency, stability of the output voltage, shielding, and thermal management. Results from a test of the magnetic field tolerance of the DC-DC converters are reported. System tests with pixel modules using many components of the future pixel barrel system are summarized. Finally first impressions from a pre-series of 200 DC-DC converters are presented.

  16. High reliability DC/DC converter module for electronic boards equipped with FPGAs

    NASA Astrophysics Data System (ADS)

    Viganò, W.; Boccardi, A.; Zamantzas, C.

    2015-01-01

    The Beam Instrumentation Group at CERN is designing a new general-purpose VME carrier module utilising several PTH04T230W DC/DC converters. These off-the-shelf converters are built with unshielded inductors and need to be mounted on the printed circuit board as stand-alone components. Thus, reducing the global manageability and increasing the total cost of the carrier module. The new design aims to develop a module with better power dissipation, efficiency and reliability. In the future, it should be also possible to be directly integrated on the mainboard. For this reason, a Buck DC/DC converter has been implemented with the following main characteristics: input range from 3.0 V to 5.5 V; output range from 0.6 V to 3.3 V, settable by means of an external resistor; output current protection at 6 A; maximum output ripple ± 50 mVpp; switching frequency of 300KHz; short circuit protection; On/Off function; EMI reduction with frequency spread spectrum; soft-start function and thermal shutdown, in a 16 × 19 mm compact size. The selected buck controller is the TPS40303 integrated circuit and drives the CSD16321 power MOSFET, both from Texas Instruments. All selected components have been used at a minimum derating of 50% to reduce component stress and increase the reliability of this module. The selected inductors, i.e. Bourns SRP1055, are the main contributor for the high efficiency (95%), due to their very low equivalent series resistance. On the 4-layer PCB comprising all the components of this module, a snubber circuit, for further reduction of the output ripple due to the MOSFET ringing, can be mounted optionally. It is left as an option due to its effect on the total efficiency. The board layout has been optimized for maximum heat transfer and it can be used without active cooling. The board can maintain the maximum temperature on its surface, while at maximum current output, below 55°C at 25°C ambient temperature. An example of the electrical performance

  17. Electrodeposited Nanolaminated CoNiFe Cores for Ultracompact DC-DC Power Conversion

    SciTech Connect

    Kim, J; Kim, M; Herrault, F; Park, JY; Allen, MG

    2015-09-01

    Laminated metallic alloy cores (i.e., alternating layers of thin film metallic alloy and insulating material) of appropriate lamination thickness enable suppression of eddy current losses at high frequencies. Magnetic cores comprised of many such laminations yield substantial overall magnetic volume, thereby enabling high-power operation. Previously, we reported nanolaminated permalloy (Ni-80 Fe-20) cores based on a sequential electrodeposition technique, demonstrating negligible eddy current losses at peak flux densities up to 0.5 T and operating at megahertz frequencies. This paper demonstrates improved performance of nanolaminated cores comprising tens to hundreds of layers of 300-500-nm-thick CoNiFe films that exhibit superior magnetic properties (e.g., higher saturation flux density and lower coercivity) than permalloy. Nanolaminated CoNiFe cores can be operated up to a peak flux density of 0.9 T, demonstrating improved power handling capacity and exhibiting 30% reduced volumetric core loss, attributed to lowered hysteresis losses compared to the nanolaminated permalloy core of the same geometry. Operating these cores in a buck dc-dc power converter at a switching frequency of 1 MHz, the nanolaminated CoNiFe cores achieved a conversion efficiency exceeding 90% at output power levels up to 7 W, compared to an achieved permalloy core conversion efficiency below 86% at 6 W.

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

    PubMed Central

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

    2014-01-01

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

  19. A 66pW Discontinuous Switch-Capacitor Energy Harvester for Self-Sustaining Sensor Applications

    PubMed Central

    Wu, Xiao; Shi, Yao; Jeloka, Supreet; Yang, Kaiyuan; Lee, Inhee; Sylvester, Dennis; Blaauw, David

    2016-01-01

    We present a discontinuous harvesting approach for switch capacitor DC-DC converters that enables ultra-low power energy harvesting. By slowly accumulating charge on an input capacitor and then transferring it to a battery in burst-mode, switching and leakage losses in the DC-DC converter can be optimally traded-off with the loss due to non-ideal MPPT operation. The harvester uses a 15pW mode controller, an automatic conversion ratio modulator, and a moving sum charge pump for low startup energy upon a mode switch. In 180nm CMOS, the harvester achieves >40% end-to-end efficiency from 113pW to 1.5μW with 66pW minimum input power, marking a >10× improvement over prior ultra-low power harvesters.

  20. Fuzzy logic mode switching in helicopters

    NASA Technical Reports Server (NTRS)

    Sherman, Porter D.; Warburton, Frank W.

    1993-01-01

    The application of fuzzy logic to a wide range of control problems has been gaining momentum internationally, fueled by a concentrated Japanese effort. Advanced Research & Development within the Engineering Department at Sikorsky Aircraft undertook a fuzzy logic research effort designed to evaluate how effective fuzzy logic control might be in relation to helicopter operations. The mode switching module in the advanced flight control portion of Sikorsky's motion based simulator was identified as a good candidate problem because it was simple to understand and contained imprecise (fuzzy) decision criteria. The purpose of the switching module is to aid a helicopter pilot in entering and leaving coordinated turns while in flight. The criteria that determine the transitions between modes are imprecise and depend on the varied ranges of three flight conditions (i.e., simulated parameters): Commanded Rate, Duration, and Roll Attitude. The parameters were given fuzzy ranges and used as input variables to a fuzzy rulebase containing the knowledge of mode switching. The fuzzy control program was integrated into a real time interactive helicopter simulation tool. Optimization of the heading hold and turn coordination was accomplished by interactive pilot simulation testing of the handling quality performance of the helicopter dynamic model. The fuzzy logic code satisfied all the requirements of this candidate control problem.

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

    DOEpatents

    Shimer, Daniel W.; Lange, Arnold C.

    1995-01-01

    A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules.

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

    DOEpatents

    Shimer, D.W.; Lange, A.C.

    1995-05-23

    A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules. 5 Figs.

  3. Low-to-Medium Power Single Chip Digital Controlled DC-DC Regulator for Point-of-Load Applications

    NASA Technical Reports Server (NTRS)

    Adell, Philippe C. (Inventor); Bakkaloglu, Bertan (Inventor); Vermeire, Bert (Inventor); Liu, Tao (Inventor)

    2015-01-01

    A DC-DC converter for generating a DC output voltage includes: a digitally controlled pulse width modulator (DPWM) for controlling a switching power stage to supply a varying voltage to an inductor; and a digital voltage feedback circuit for controlling the DPWM in accordance with a feedback voltage corresponding to the DC output voltage, the digital voltage feedback circuit including: a first voltage controlled oscillator for converting the feedback voltage into a first frequency signal and to supply the first frequency signal to a first frequency discriminator; a second voltage controlled oscillator for converting a reference voltage into a second frequency signal and to supply the second frequency signal to a second frequency discriminator; a digital comparator for comparing digital outputs of the first and second frequency discriminators and for outputting a digital feedback signal; and a controller for controlling the DPWM in accordance with the digital feedback signal.

  4. Robust DC/DC converter control for polymer electrolyte membrane fuel cell application

    NASA Astrophysics Data System (ADS)

    Wang, Ya-Xiong; Yu, Duck-Hyun; Chen, Shi-An; Kim, Young-Bae

    2014-09-01

    This study investigates a robust controller in regulating the pulse width modulation (PWM) of a DC/DC converter for a polymer electrolyte membrane fuel cell (PEMFC) application. A significant variation in the output voltage of a PEMFC depends on the power requirement and prevents a PEMFC from directly connecting to a subsequent power bus. DC/DC converters are utilized to step-up or step-down voltage to match the subsequent power bus voltage. In this study, a full dynamic model, which includes a PEMFC and boost and buck DC/DC converters, is developed under MATLAB/Simulink environment for control. A robust PWM duty ratio control for the converters is designed using time delay control (TDC). This control enables state variables to accurately follow the dynamics of a reference model using time-delayed information of plant input and output information within a few sampling periods. To prove the superiority of the TDC performance, traditional proportional-integral control (PIC) and model predictive control (MPC) are designed and implemented, and the simulation results are compared. The efficacies of TDC for the PEMFC-fed PWM DC/DC converters are validated through experimental test results using a 100 W PEMFC as well as boost and buck DC/DC converters.

  5. Development of a fuzzy logic controller for dc/dc converters: Design, computer simulation, and experimental evaluation

    SciTech Connect

    So, W.C.; Tse, C.K.; Lee, Y.S.

    1996-01-01

    The design of a fuzzy logic controller for dc/dc converters is described in this paper. A brief review of fuzzy logic and its application to control is first given. Then, the derivation of a fuzzy control algorithm for regulating dc/dc converters is described in detail. The proposed fuzzy control is evaluated by computer simulations as well as experimental measurements of the closed-loop performance of simple dc/dc converters in respect of load regulation and line regulation.

  6. Test Results of Selected Commercial DC/DC Converters under Cryogenic Temperatures - A Digest

    NASA Technical Reports Server (NTRS)

    Patterson, Richard; Hammoud, Ahmad

    2010-01-01

    DC/DC converters are widely used in space power systems in the areas of power management and distribution, signal conditioning, and motor control. Design of DC/DC converters to survive cryogenic temperatures will improve the power system performance, simplify design, and reduce development and launch costs. In this work, the performance of nine COTS modular, low-tomedium power DC/DC converters was investigated under cryogenic temperatures. The converters were evaluated in terms of their output regulation, efficiency, and input and output currents. At a given temperature, these properties were obtained at various input voltages and at different load levels. A summary on the performance of the tested converters was given. More comprehensive testing and in-depth analysis of performance under long-term exposure to extreme temperatures are deemed necessary to establish the suitability of these and other devices for use in the harsh environment of space exploration missions.

  7. DC-DC converters with reduced mass for trackers at the HL-LHC

    NASA Astrophysics Data System (ADS)

    Affolder, A.; Allongue, B.; Blanchot, G.; Faccio, F.; Fuentes, C.; Greenall, A.; Michelis, S.

    2011-11-01

    The development at CERN of low noise DC-DC converters for the powering of front-end systems enables the implementation of efficient powering schemes for the physics experiments at the HL-LHC. Recent tests made on the ATLAS short strip tracker modules confirm the full electromagnetic compatibility of the DC-DC converter prototypes with front-end detectors. The integration of the converters in the trackers front-ends needs to address also the material budget constraints. The impact of the DC-DC converters onto the material budget of the ATLAS tracker modules is discussed and mass reduction techniques are explored, leading to a compromise between electromagnetic compatibility and mass. Low mass shield implementations and Aluminum core inductors are proposed. Also, the impact on emitted noise due to a size reduction of critical components is discussed. Finally, material reduction techniques are discussed at the board layout and manufacturing levels.

  8. Power Strategy in DC/DC Converters to Increase Efficiency of Electrical Stimulators

    PubMed Central

    Aqueveque, Pablo; Acuña, Vicente; Saavedra, Francisco; Debelle, Adrien; Lonys, Laurent; Julémont, Nicolas; Huberland, François; Godfraind, Carmen; Nonclercq, Antoine

    2016-01-01

    Power efficiency is critical for electrical stimulators. Battery life of wearable stimulators and wireless power transmission in implanted systems are common limiting factors. Boost DC/DC converters are typically needed to increase the supply voltage of the output stage. Traditionally, boost DC/DC converters are used with fast control to regulate the supply voltage of the output. However, since stimulators are acting as current sources, such voltage regulation is not needed. Banking on this, this paper presents a DC/DC conversion strategy aiming to increase power efficiency. It compares, in terms of efficiency, the traditional use of boost converters to two alternatives that could be implemented in future hardware designs. PMID:27990232

  9. DC/DC Power Converter for Super-Capacitor Supplied by Electric Power Splitter

    NASA Astrophysics Data System (ADS)

    Haubert, T.; Mindl, P.

    The aim of the article is design of DC/DC converter and discussing of problematic supply using electric power splitter. The electric power splitter with AC/DC converter is source for the DC/DC converter, which is dedicated for charging and discharging of hybrid car drive super-capacitor energy storage. The electric power splitter is synchronous machine with two rotating parts. First rotor contains permanent magnet and the second rotor contains three-phase windings. The amplitude of output voltage depends on difference between first and second rotor speed. The main role of the DC/DC converter is to optimize energy content in super-capacitor storage used to acceleration and deceleration driving period of the passenger car with hybrid electric vehicle (HEV) drive system using electric power splitter.

  10. Modelling and Simulation of Digital Compensation Technique for dc-dc Converter by Pole Placement

    NASA Astrophysics Data System (ADS)

    Shenbagalakshmi, R.; Sree Renga Raja, T.

    2015-09-01

    A thorough and effective analysis of the dc-dc converters is carried out in order to achieve the system stability and to improve the dynamic performance. A small signal modelling based on state space averaging technique for dc-dc converters is carried out. A digital state feedback gain matrix is derived by pole placement technique in order to achieve the stability of a completely controllable system. A prediction observer for the dc-dc converters is designed and a dynamic compensation (observer plus control law) is provided using separation principle. The output is very much improved with zero output voltage ripples, zero peak overshoot, and much lesser settling time in the range of ms and with higher overall efficiency (>90 %).

  11. Application handbook for a Standardized Control Module (SCM) for DC-DC converters, volume 1

    NASA Technical Reports Server (NTRS)

    Lee, F. C.; Mahmoud, M. F.; Yu, Y.

    1980-01-01

    The standardized control module (SCM) was developed for application in the buck, boost and buck/boost DC-DC converters. The SCM used multiple feedback loops to provide improved input line and output load regulation, stable feedback control system, good dynamic transient response and adaptive compensation of the control loop for changes in open loop gain and output filter time constraints. The necessary modeling and analysis tools to aid the design engineer in the application of the SCM to DC-DC Converters were developed. The SCM functional block diagram and the different analysis techniques were examined. The average time domain analysis technique was chosen as the basic analytical tool. The power stage transfer functions were developed for the buck, boost and buck/boost converters. The analog signal and digital signal processor transfer functions were developed for the three DC-DC Converter types using the constant on time, constant off time and constant frequency control laws.

  12. Advanced DC/DC Converters Towards Higher Volumetric Efficiencies For Space Applications

    NASA Technical Reports Server (NTRS)

    Shaw, Harry; Shue, Jack; Liu, David; Wang, Bright; Plante, Jeanette

    2005-01-01

    A new emphasis on planetary exploration by NASA drives the need for small, high power DC/DC converters which are functionally modular. NASA GSFC and other government space organizations are supporting technology development in the DC/DC converter area to both meet new needs and to promote more sources of supply. New technologies which enable miniaturization such as embedded passive technologies and thermal management using high thermal conductivity materials are features of the new designs. Construction of some simple DC/DC converter core circuits using embedded components was found to be successful for increasing volumetric efficiency to 37 W/inch. The embedded passives were also able to perform satisfactorily in this application in cryogenic temperatures.

  13. Efficiency and Regulation of Commercial Low Power DC/DC Converter Modules at Low Temperatures

    NASA Technical Reports Server (NTRS)

    Elbuluk, Malik E.; Gerber, Scott; Hammoud, Ahmad; Patterson, Richard L.

    2000-01-01

    DC/DC converters that are capable of operating at cryogenic temperatures are anticipated to play an important role in the power systems of future NASA deep space missions. Design of these converters to survive cryogenic temperatures will improve the power system performance, and reduce development and launch costs. At the NASA Glenn Research Center Low Temperature Electronics Laboratory, several commercial off-the-shelf dc/dc converter modules were evaluated for their low temperature performance. Various parameters were investigated as a function of temperature, in the range of 20 C to -190 C. Data pertaining to the efficiency and voltage regulation of the tested converters is presented and discussed.

  14. Analysis of high voltage step-up nonisolated DC-DC boost converters

    NASA Astrophysics Data System (ADS)

    Alisson Alencar Freitas, Antônio; Lessa Tofoli, Fernando; Junior, Edilson Mineiro Sá; Daher, Sergio; Antunes, Fernando Luiz Marcelo

    2016-05-01

    A high voltage step-up nonisolated DC-DC converter based on coupled inductors suitable to photovoltaic (PV) systems applications is proposed in this paper. Considering that numerous approaches exist to extend the voltage conversion ratio of DC-DC converters that do not use transformers, a detailed comparison is also presented among the proposed converter and other popular topologies such as the conventional boost converter and the quadratic boost converter. The qualitative analysis of the coupled-inductor-based topology is developed so that a design procedure can be obtained, from which an experimental prototype is implemented to validate the theoretical assumptions.

  15. Asynchronous Transfer Mode (ATM) Switch Technology and Vendor Survey

    NASA Technical Reports Server (NTRS)

    Berry, Noemi

    1995-01-01

    Asynchronous Transfer Mode (ATM) switch and software features are described and compared in order to make switch comparisons meaningful. An ATM switch's performance cannot be measured solely based on its claimed switching capacity; traffic management and congestion control are emerging as the determining factors in an ATM network's ultimate throughput. Non-switch ATM products and experiences with actual installations of ATM networks are described. A compilation of select vendor offerings as of October 1994 is provided in chart form.

  16. 75 FR 17433 - In the Matter of Certain DC-DC Controllers and Products Containing Same; Notice of Commission...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-06

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION In the Matter of Certain DC-DC Controllers and Products Containing Same; Notice of Commission... certain DC-DC controllers by reason of infringement of certain claims of U.S. Patent Nos. 7,315,190; 6,414...

  17. 75 FR 65651 - In the Matter of Certain DC-DC Controllers and Products Containing Same; Notice of Commission...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-26

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION In the Matter of Certain DC-DC Controllers and Products Containing Same; Notice of Commission... DC-DC controllers by reason of infringement ] of certain claims of U.S. Patent Nos. 7,315,190; 6,414...

  18. 75 FR 28283 - In the Matter of: Certain DC-DC Controllers and Products Containing Same; Notice of Commission...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-20

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION In the Matter of: Certain DC-DC Controllers and Products Containing Same; Notice of Commission... importation of certain DC-DC controllers by reason of infringement of certain claims of U.S. Patent Nos. 7,315...

  19. 75 FR 65655 - In the Matter of Certain DC-DC Controllers and Products Containing Same; Notice of Commission...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-26

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION In the Matter of Certain DC-DC Controllers and Products Containing Same; Notice of Commission... DC-DC controllers by reason of infringement of certain claims of U.S. Patent Nos. 7,315,190; 6,414...

  20. Modelling, Simulation and Construction of a DC/DC Boost Power Converter: A School Experimental System

    ERIC Educational Resources Information Center

    Silva-Ortigoza, R.; Silva-Ortigoza, G.; Hernandez-Guzman, V. M.; Saldana-Gonzalez, G.; Marcelino-Aranda, M.; Marciano-Melchor, M.

    2012-01-01

    We introduce a dc/dc boost power converter as a didactic prototype intended to support courses on electric circuit analysis experimentally. The corresponding mathematical model is obtained, the converter is designed and an experimental setup is described, constructed and tested. Simplicity of construction as well as low cost of components renders…

  1. DC-DC conversion powering schemes for the CMS tracker at Super-LHC

    NASA Astrophysics Data System (ADS)

    Klein, K.; Feld, L.; Jussen, R.; Karpinski, W.; Merz, J.; Sammet, J.

    2010-07-01

    The CMS experiment at the Large Hadron Collider (LHC) at CERN, Geneva, houses the largest silicon strip tracker ever built. For the foreseen luminosity upgrade of the LHC, the Super-LHC, however, a completely new silicon tracker will have to be constructed. One out of several major improvements currently under consideration is the implementation of a track trigger, with tracking information being provided to the first level trigger. Such an intelligent tracker design, utilising fast digital readout electronics, will most certainly lead to an increased power consumption, compared to today's tracker. In combination with the desire to reduce the amount of passive material inside the tracking volume and the impracticality to exchange or even add additional supply cables, a novel powering scheme will be inevitable. In this article a powering scheme based on DC-DC conversion is proposed, and requirements for the DC-DC converters are discussed. Studies of important DC-DC converter quantities such as the power efficiency, conducted and radiated noise levels, and material budget are presented, and a possible implementation of DC-DC buck converters into one proposed track trigger layout is sketched.

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

    SciTech Connect

    Claudio H. Rivetta et al.

    2001-09-24

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

  3. Modelling, Simulation and Construction of a DC/DC Boost Power Converter: A School Experimental System

    ERIC Educational Resources Information Center

    Silva-Ortigoza, R.; Silva-Ortigoza, G.; Hernandez-Guzman, V. M.; Saldana-Gonzalez, G.; Marcelino-Aranda, M.; Marciano-Melchor, M.

    2012-01-01

    We introduce a dc/dc boost power converter as a didactic prototype intended to support courses on electric circuit analysis experimentally. The corresponding mathematical model is obtained, the converter is designed and an experimental setup is described, constructed and tested. Simplicity of construction as well as low cost of components renders…

  4. Regulation of a lightweight high efficiency capacitator diode voltage multiplier dc-dc converter

    NASA Technical Reports Server (NTRS)

    Harrigill, W. T., Jr.; Myers, I. T.

    1976-01-01

    A method for the regulation of a capacitor diode voltage multiplier dc-dc converter has been developed which has only minor penalties in weight and efficiency. An auxiliary inductor is used, which only handles a fraction of the total power, to control the output voltage through a pulse width modulation method in a buck boost circuit.

  5. Regulation of a lightweight high efficiency capacitor diode voltage multiplier dc-dc converter

    NASA Technical Reports Server (NTRS)

    Harrigill, W. T., Jr.; Myers, I. T.

    1976-01-01

    A method for the regulation of a capacitor diode voltage multiplier dc-dc converter has been developed which has only minor penalties in weight and efficiency. An auxiliary inductor is used, which only handles a fraction of the total power, to control the output voltage through a pulse width modulation method in a buck boost circuit.

  6. Modular AC Nano-Grid with Four-Quadrant Micro-Inverters and High-Efficiency DC-DC Conversion

    NASA Astrophysics Data System (ADS)

    Poshtkouhi, Shahab

    A significant portion of the population in developing countries live in remote communities, where the power infrastructure and the required capital investment to set up local grids do not exist. This is due to the fuel shipment and utilization costs required for fossil fuel based generators, which are traditionally used in these local grids, as well as high upfront costs associated with the centralized Energy Storage Systems (ESS). This dissertation targets modular AC nano-grids for these remote communities developed at minimal capital cost, where the generators are replaced with multiple inverters, connected to either Photovoltaic (PV) or battery modules, which can be gradually added to the nano-grid. A distributed droop-based control architecture is presented for the PV and battery Micro-Inverters (MIV) in order to achieve frequency and voltage stability, as well as active and reactive power sharing. The nano-grid voltage is regulated collectively in either one of four operational regions. Effective load sharing and transient handling are demonstrated experimentally by forming a nano-grid which consists of two custom 500 W MIVs. The MIVs forming the nano-grid have to meet certain requirements. A two-stage MIV architecture and control scheme with four-quadrant power-flow between the nano-grid, the PV/battery and optional short-term storage is presented. The short-term storage is realized using high energy-density Lithium-Ion Capacitor (LIC) technology. A real-time power smoothing algorithm utilizing LIC modules is developed and tested, while the performance of the 100 W MIV is experimentally verified under closed-loop dynamic conditions. Two main limitations of the DAB topology, as the core of the MIV architecture's dc-dc stage, are addressed: 1) This topology demonstrates poor efficiency and limited regulation accuracy at low power. These are improved by introducing a modified topology to operate the DAB in Flyback mode, achieving up to an 8% increase in

  7. Optical mode switch based on multimode interference couplers

    NASA Astrophysics Data System (ADS)

    Xiao, Huifu; Deng, Lin; Zhao, Guolin; Liu, Zilong; Meng, Yinghao; Guo, Xiaonan; Liu, Guipeng; Liu, Su; Ding, Jianfeng; Tian, Yonghui

    2017-02-01

    In this paper, we propose an optical mode switch based on two cascaded multimode interference (MMI) couplers. After a fundamental mode divided into two equal-power fundamental modes in the first MMI coupler, the thermo-optic effect is employed to modulate the phase of the two fundamental modes before directed to the next MMI for the purpose of mode switching. By adjusting the electric signals applied to the modulation arms, the proposed device can implement mode switching in three states: (a) one first-order and two fundamental modes simultaneously output, (b) one first-order mode output, and (c) two fundamental modes output. As a result, the simulated excess losses are -0.29 dB, -0.10 dB, and -0.63 dB, respectively.

  8. Comparative Performance Analysis of Sliding Mode and Q-Controller Algorithms for Buck Converter

    NASA Astrophysics Data System (ADS)

    Pati, Nivedita

    2017-08-01

    The switched mode dc-dc converters are some of the simplest power electronic circuits which have received an increasing deal of interest in many areas due to their high efficiency and small size. These converters are non-linear and time-variant in nature; hence the analysis, control and stabilization are the main factors that need to be considered. Many control methodology are used for control of switch mode dc-dc converters but the optimum one is always in demand. This paper presents the linearization of the Buck converter model and a comparison between a linear and non-linear control algorithms for better output voltage regulation along with robustness to change in input voltage and load parameters. The computer –aided design software tool Matlab/Simulink is used for the simulations and the results are presented.

  9. 77 FR 69501 - Certain DC-DC Controllers and Products Containing Same; Decision To Affirm-in-Part, Reverse-in...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-19

    ... COMMISSION Certain DC-DC Controllers and Products Containing Same; Decision To Affirm-in-Part, Reverse-in... importing, offering for sale, and selling for importation into the United States DC-DC controllers or... claims 29 and 34 of the '470 patent are directly infringed by respondent uPI's accused DC-DC controllers...

  10. Mode Switching Control for Personal Mobility Robot

    NASA Astrophysics Data System (ADS)

    Hirose, Noriaki; Sukigara, Kazutoshi; Kajima, Hideki; Yamaoka, Masaaki

    The present paper introduces a novel standing-up control strategy based on Initial Value Compensation (IVC) for a Personal Mobility Robot (PMR). PMRs, which are wheeled-inverted-pendulum-type mobility-assist devices, offer the following advantages: (1) they can turn at a point; (2) they can maintain a level seating posture on a slope; and (3) they have a smaller footprint than conventional electric wheelchairs with four wheels. On the other hand, the user must maintain the posture of the PMR by using additional assist wheels on the ground when mounting/dismounting the PMR and working while seated on the PMR. In order to satisfy these requirements, we propose the following approach. First, the PMR accelerates to lift its assist wheels off the ground and determines whether the assist wheels are in contact with the ground. The feedback controller is then switched to wheeled-inverted-pendulum mode using the proposed IVC. The proposed IVC is designed such that the transient responses are improved and the amplitude of the control input and the jerk component are suppressed, in order to reduce the shock felt by the driver. The effectiveness of the proposed approach has been verified by conducting numerical simulations and experiments using a prototype PMR.

  11. Switching of Swimming Modes in Magnetospirillium gryphiswaldense

    PubMed Central

    Reufer, M.; Besseling, R.; Schwarz-Linek, J.; Martinez, V.A.; Morozov, A.N.; Arlt, J.; Trubitsyn, D.; Ward, F.B.; Poon, W.C.K.

    2014-01-01

    The microaerophilic magnetotactic bacterium Magnetospirillum gryphiswaldense swims along magnetic field lines using a single flagellum at each cell pole. It is believed that this magnetotactic behavior enables cells to seek optimal oxygen concentration with maximal efficiency. We analyze the trajectories of swimming M. gryphiswaldense cells in external magnetic fields larger than the earth’s field, and show that each cell can switch very rapidly (in <0.2 s) between a fast and a slow swimming mode. Close to a glass surface, a variety of trajectories were observed, from straight swimming that systematically deviates from field lines to various helices. A model in which fast (slow) swimming is solely due to the rotation of the trailing (leading) flagellum can account for these observations. We determined the magnetic moment of this bacterium using a to our knowledge new method, and obtained a value of (2.0±0.6)×10−16 A · m2. This value is found to be consistent with parameters emerging from quantitative fitting of trajectories to our model. PMID:24411235

  12. The mode switching of PSR B2020+28

    NASA Astrophysics Data System (ADS)

    Wen, Z. G.; Wang, N.; Yan, W. M.; Yuan, J. P.; Liu, Z. Y.; Chen, M. Z.; Chen, J. L.

    2016-08-01

    This paper reports on polarimetric radiation properties based on the switching modes of normal PSR B2020+28 by analyzing the data acquired from the Nanshan 25-m radio telescope at 1556 MHz. With nearly 8 hours quasi-continuous observation, the data presented some striking and updated phenomena. The change of relative intensity between the leading and trailing components is the predominant feature of mode switching. The intensity ratio between the leading and trailing components are measured for the individual profiles averaged over 30 seconds. It is found that there is an excess of high ratios over the normal distribution, which indicates that two modes exist in the pulsar. The distribution of abnormal mode has a narrower width indicating that the abnormal mode is more stable than the normal mode. A total of 76 mode switching events are detected in our data. It spends 89 % in the normal mode and 11 % in the abnormal mode. The intrinsic distributions of mode timescales are constrained with power-law distributions. The significant difference in the index of the duration distribution between normal and abnormal modes possibly indicates that the timescale for the abnormal mode to get stable is shorter than that for the normal mode. The frequent switching between both modes may indicate that the oscillations between different magnetospheric states are rapid.

  13. DC-DC power converter research for Orbiter/Station power exchange

    NASA Technical Reports Server (NTRS)

    Ehsani, M.

    1993-01-01

    This project was to produce innovative DC-DC power converter concepts which are appropriate for the power exchange between the Orbiter and the Space Station Freedom (SSF). The new converters must interface three regulated power buses on SSF, which are at different voltages, with three fuel cell power buses on the Orbiter which can be at different voltages and should be tracked independently. Power exchange is to be bi-directional between the SSF and the Orbiter. The new converters must satisfy the above operational requirements with better weight, volume, efficiency, and reliability than is available from the present conventional technology. Two families of zero current DC-DC converters were developed and successfully adapted to this application. Most of the converters developed are new and are presented.

  14. Cryogenic Evaluation of an Advanced DC/DC Converter Module for Deep Space Applications

    NASA Technical Reports Server (NTRS)

    Elbuluk, Malik E.; Hammoud, Ahmad; Gerber, Scott S.; Patterson, Richard

    2003-01-01

    DC/DC converters are widely used in power management, conditioning, and control of space power systems. Deep space applications require electronics that withstand cryogenic temperature and meet a stringent radiation tolerance. In this work, the performance of an advanced, radiation-hardened (rad-hard) commercial DC/DC converter module was investigated at cryogenic temperatures. The converter was investigated in terms of its steady state and dynamic operations. The output voltage regulation, efficiency, terminal current ripple characteristics, and output voltage response to load changes were determined in the temperature range of 20 to -140 C. These parameters were obtained at various load levels and at different input voltages. The experimental procedures along with the results obtained on the investigated converter are presented and discussed.

  15. Adaptive output voltage tracking controller for uncertain DC/DC boost converter

    NASA Astrophysics Data System (ADS)

    Lee, Byoung-Seoup; Kim, Seok-Kyoon; Park, Jin-Hyuk; Lee, Kyo-Beum

    2016-06-01

    This paper presents a cascade output voltage control strategy for an uncertain DC/DC boost converter adopting an adaptive current controller in its inner loop. Considering the non-linearity, load uncertainties and parameter uncertainties of the converter, the proposed controller is designed following the conventional cascade voltage controller design method. The proposed method makes the following three contributions. First, a coordinate transformation is introduced for the inner loop, enabling avoidance of the singularity problem caused by the estimates of uncertain parameters. Second, a slight modification to the adaptation law is performed to guarantee closed-loop stability in the presence of the time-varying component of the load current. Third, the outer-loop controller is devised such that its performance can be adjusted without any parameter information. The closed-loop performance is demonstrated through simulations and experiments using the DSP28335 with a 3 kW DC/DC boost converter.

  16. ITAR Free Commercial-of-the-Shelf DC/DC Converter

    NASA Astrophysics Data System (ADS)

    Denzinger, Wolfgang; Hintze, Thomas

    2014-08-01

    A commercial-of-the-shelf (COTS) DC/DC converter for digital space equipment has been developed by ASP under ESA contract with special emphasis on low cost, no use of ITAR listed EEE parts like Mosfets, minimum number of rad-hard digital IC's and a design tolerance against single event effects by appropriate filtering. However, the intention to qualify this discrete converter design for a low cost FM series production was difficult due to the high up-sceening cost of EEE-parts with one lot guarantee and minimum-by. To overcome this problem, in a next step a redesign of the DC/DC converter was performed with all semiconductors like bipolar transistors, rectifiers and zener diodes packaged into hybrids. With this approach it was possible to buy a high number of less expensive wafers or dies from one lot, to perform a lot acceptance test and to integrate the dies into hybrid packages with further up- screening for FM use. The semiconductors have been packaged into three signal hybrids with 44 pins and one power hybrid with 24 pins for the dissipating transistors and rectifiers. The design of the hybrids is such, that all integrated semiconductors can be tested individually. The qualification of four EQM DC/DC converters with different combinations of output voltages has been successfully performed and two FM's have been manufactured and tested.

  17. Unified switching mechanism for reversible change between unipolar and bipolar switching modes of oxide resistive switching memory devices

    NASA Astrophysics Data System (ADS)

    Choi, Sang-Jun; Kim, Ki-Hong; Yang, Woo-Young; Kim, Sohyeon; Oh, Semi; Kim, Kyoung-Kook; Kim, Yunkyung; Hong, Minki; Nam, Kiyoung; Cho, Soohaeng

    2017-05-01

    We demonstrate the coexistence of the unipolar and bipolar switching behaviors in a single oxide resistive device composed of Pt-CuO0.8-W structure and we reveal the switching mechanism by the comprehensive analyses of both unipolar and bipolar switching behaviors. The observations suggest that the RESET (turning OFF) mechanism of unipolar and bipolar switching modes can be explained by a unified scheme. The results also elucidate that the SET (turning ON) process in bipolar mode is originated from by the drift of ions though charged vacancies, while the SET process in unipolar mode is explained by electron tunneling through vacancies. The proposed model successfully explains the observations of resistive switching of our device regardless of input voltage polarity and, more importantly, we propose a way to selectively choose one specific operation mode.

  18. First Implementation of a two-stage DC-DC conversion powering scheme for the CMS Phase-2 outer tracker

    NASA Astrophysics Data System (ADS)

    Feld, L.; Gadek, T.; Karpinski, W.; Klein, K.; Lipinski, M.; Pauls, A.; Preuten, M.; Rauch, M.; Wangelik, F.; Wlochal, M.

    2017-03-01

    The ``2S'' silicon strip modules for the CMS Phase-2 tracker upgrade will require two operating voltages. These will be provided via a two-step DC-DC conversion powering scheme, in which one DC-DC converter delivers 2.5 V while the second DC-DC converter receives 2.5 V at its input and converts it to 1.2 V. The DC-DC converters will be mounted on a flex PCB, the service hybrid, together with an opto-electrical converter module (VTRx+) and a serializer (LP-GBT). The service hybrid will be mounted directly on the 2S module. A prototype service hybrid has been developed and its performance has been evaluated, including radiative and conductive noise emissions, and efficiency. In addition system tests with a prototype module have been performed. In this work the service hybrid will be described and the test results will be summarized.

  19. Analysis of a transformer-less, multi-level DC-DC converter for HVDC operation

    SciTech Connect

    Karady, G.G.; Devarajan, S.

    1998-12-31

    HVDC systems require DC step up and DC step down units. The traditional approach is the application of twelve-pulse thyristor bridges with transformers. The developments of fast switching IGBT devices permit the development of transformer-less, multi-level converters. A multi-level circuit was suggested by Limpaecher. This paper presents a detailed simulation of the proposed circuit together with the analysis of its performance. The converter consists of a set of capacitors, air core inductors and solid state switches arranged in a ladder network. In the step-up mode, the closing of solid state switches resonantly charges the capacitors in parallel through an air-cored inductor. Then solid state switches resonantly charges the capacitors in parallel through an air-cored inductor. Then solid state switches connect the capacitors in series and discharge them through an air-core inductor to the load. In the step-down mode the capacitors are charged in series and discharged in parallel. The circuit has three modes of operation in each cycle: charge, inversion, and discharge. The circuit operation is analyzed in each mode using SPICE simulations. The selection of the components is discussed and output voltage regulation is analyzed. The results show that the proposed circuit promises significant reduction of losses, because of the zero current switching. The investment cost is reduced because of the elimination of transformers.

  20. Fabrication of a Zn-Ferrite Thick Film Planar Power Inductor for DC-DC Converter LSI Package

    NASA Astrophysics Data System (ADS)

    Okazaki, Shinya; Takeuchi, Asako; Takeshima, Akihiro; Sonehara, Makoto; Sato, Toshiro; Matsushita, Nobuhiro

    In order to realize the “POL (Point of Load)” dc-dc converter for LSIs, a Zn-ferrite thick film planar power inductor embedded in LSI package has been fabricated and evaluated in this study. 10 μm thick spin-sprayed Zn ferrite film with a high saturation magnetization of 0.57 T was introduced to the magnetic core for planer power inductor consisting of a 20 μm thick, 650 μm square, 2-turn inner copper spiral coil sandwiched by top and bottom magnetic core. Zn ferrite film had a natural resonance frequency of 500 MHz and a static relative permeability of 80. The planar power inductor with a footprint of 850×850 μm exhibited a 10 nH inductance and a quality factor of 20 at 100 MHz. The degradation of inductance owing to the superimposed dc current of 2A was 17%. The planar power inductor will be applied to low-voltage converter with hundreds megahertz switching operation in the future.

  1. DC-DC Type High-Frequency Link DC for Improved Power Quality of Cascaded Multilevel Inverter

    NASA Astrophysics Data System (ADS)

    Sadikin, Muhammad; Senjyu, Tomonobu; Yona, Atsushi

    2013-06-01

    Multilevel inverters are emerging as a new breed of power converter options for power system applications. Recent advances in power switching devices enabled the suitability of multilevel inverters for high voltage and high power applications because they are connecting several devices in series without the need of component matching. Usually, a transformerless battery energy storage system, based on a cascaded multilevel inverter, is used as a measure for voltage and frequency deviations. System can be reduced in size, weight, and cost of energy storage system. High-frequency link circuit topology is advantageous in realizing compact and light-weight power converters for uninterruptible power supply systems, new energy systems using photovoltaic-cells, fuel-cells and so on. This paper presents a DC-DC type high-frequency link DC (HFLDC) cascaded multilevel inverter. Each converter cell is implemented a control strategy for two H-bridge inverters that are controlled with the same multicarrier pulse width modulation (PWM) technique. The proposed cascaded multilevel inverter generates lower voltage total harmonic distortion (THD) in comparison with conventional cascaded multilevel inverter. Digital simulations are carried out using PSCAD/EMTDC to validate the performance of the proposed cascaded multilevel inverter.

  2. Estimation of Bidirectional Buck/boost DC/DC Converters with Electric Double-Layer Capacitors for Energy Storage Systems

    NASA Astrophysics Data System (ADS)

    Funabiki, Shigeyuki; Yamamoto, Masayoshi

    Renewable energy such as wind force and solar light has collected the attention as alternative energy sources of fossil fuel. An energy storage system with an electric double-layer capacitor (EDLC), which balances the demand and supply power, is required in order to introduce the electric power generating system that utilizes renewable energy. Currently, the research and development of these energy storage systems are actively carried out. In the energy storage system with an EDLC, the DC/DC converter having the function of the bidirectional power flow and the buck/boost performance is essential as an interface and power control circuit. There are two types of the bidirectional buck/boost DC/DC converters. One type consists of two buck/boost DC/DC converters with one reactor. The other type consists of two sets of two-quadrant DC/DC converters with one reactor. This paper discusses the comparison of these types of DC/DC converters with bidirectional power flow and buck/boost performance. The two types of DC/DC converters are estimated for their application to the energy storage system with the EDLC. As the voltage endurance of the device is lower and the mean current is smaller in the latter type of converter despite of having twice the number of devices compared to the former, the latter type of converter has the advantage of a smaller reactor, i.e., core volume and loss, and lower loss in the converter.

  3. DC-DC Converter Topology Assessment for Large Scale Distributed Photovoltaic Plant Architectures

    SciTech Connect

    Agamy, Mohammed S; Harfman-Todorovic, Maja; Elasser, Ahmed; Sabate, Juan A; Steigerwald, Robert L; Jiang, Yan; Essakiappan, Somasundaram

    2011-07-01

    Distributed photovoltaic (PV) plant architectures are emerging as a replacement for the classical central inverter based systems. However, power converters of smaller ratings may have a negative impact on system efficiency, reliability and cost. Therefore, it is necessary to design converters with very high efficiency and simpler topologies in order not to offset the benefits gained by using distributed PV systems. In this paper an evaluation of the selection criteria for dc-dc converters for distributed PV systems is performed; this evaluation includes efficiency, simplicity of design, reliability and cost. Based on this evaluation, recommendations can be made as to which class of converters is best fit for this application.

  4. A High Power Density DC-DC Converter for Distributed PV Architectures

    SciTech Connect

    Agamy, Mohammed S; Chi, Song; Elasser, Ahmed; Harfman-Todorovic, Maja; Jiang, Yan; Mueller, Frank; Tao, Fengfeng

    2012-06-01

    In order to maximize solar energy harvesting capabilities, power converters have to be designed for high efficiency and good MPPT and voltage/current performance. When many converters are used in distributed systems, power density also becomes an important factor as it allows for simpler system integration. In this paper a high power density string dc-dc converter suitable for distributed medium to large scale PV installation is presented. A simple partial power processing topology, implemented with all silicon carbide devices provides high efficiency as well as high power density. A 3.5kW, 100kHz converter is designed and tested to verify the proposed methods.

  5. Soft-start mechanism with coefficients Ki optimization for DC-DC power converters

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Hu, Jiajun; Chen, Houpeng; Li, Xi; Fan, Xi; Miao, Jie; Song, Zhitang

    2016-10-01

    This paper presents a fully digital-control soft start mechanism with coefficients Ki optimization for DC-DC power converters. During the soft start phase, a ladder reference voltage steps up gradually to make inductor current ramp up smoothly and overshoot voltage is minimized with the proposed coefficients Ki distribution. Simulation results show that massive inductor current can be well avoided during the soft start process with the proposed soft start mechanism, which only occupies a chip area of 300um×120um.

  6. A New Approach for High Efficiency Buck-Boost DC/DC Converters Using Series Compensation

    NASA Astrophysics Data System (ADS)

    Itoh, Jun-Ichi; Fujii, Takashi

    This paper proposes a novel concept for non-isolated buck-boost DC/DC converter and control method. The proposed concept uses a series connection converter that only regulates the differential voltage between the input and output voltage. As a result, the power converter capacity is decreased. Moreover, the proposed circuit has advantages such as improved efficiency and losses reduction. The fundamental operation, control method, and design method of the proposed circuit are described in this paper. In addition, the validity of the proposed circuit is confirmed by carrying out simulations and experiments.

  7. Effective switching frequency multiplier inverter

    DOEpatents

    Su, Gui-Jia; Peng, Fang Z.

    2007-08-07

    A switching frequency multiplier inverter for low inductance machines that uses parallel connection of switches and each switch is independently controlled according to a pulse width modulation scheme. The effective switching frequency is multiplied by the number of switches connected in parallel while each individual switch operates within its limit of switching frequency. This technique can also be used for other power converters such as DC/DC, AC/DC converters.

  8. Modeling, Dynamics, Bifurcation Behavior and Stability Analysis of a DC-DC Boost Converter in Photovoltaic Systems

    NASA Astrophysics Data System (ADS)

    Zhioua, M.; El Aroudi, A.; Belghith, S.; Bosque-Moncusí, J. M.; Giral, R.; Al Hosani, K.; Al-Numay, M.

    A study of a DC-DC boost converter fed by a photovoltaic (PV) generator and supplying a constant voltage load is presented. The input port of the converter is controlled using fixed frequency pulse width modulation (PWM) based on the loss-free resistor (LFR) concept whose parameter is selected with the aim to force the PV generator to work at its maximum power point. Under this control strategy, it is shown that the system can exhibit complex nonlinear behaviors for certain ranges of parameter values. First, using the nonlinear models of the converter and the PV source, the dynamics of the system are explored in terms of some of its parameters such as the proportional gain of the controller and the output DC bus voltage. To present a comprehensive approach to the overall system behavior under parameter changes, a series of bifurcation diagrams are computed from the circuit-level switched model and from a simplified model both implemented in PSIM© software showing a remarkable agreement. These diagrams show that the first instability that takes place in the system period-1 orbit when a primary parameter is varied is a smooth period-doubling bifurcation and that the nonlinearity of the PV generator is irrelevant for predicting this phenomenon. Different bifurcation scenarios can take place for the resulting period-2 subharmonic regime depending on a secondary bifurcation parameter. The boundary between the desired period-1 orbit and subharmonic oscillation resulting from period-doubling in the parameter space is obtained by calculating the eigenvalues of the monodromy matrix of the simplified model. The results from this model have been validated with time-domain numerical simulation using the circuit-level switched model and also experimentally from a laboratory prototype. This study can help in selecting the parameter values of the circuit in order to delimit the region of period-1 operation of the converter which is of practical interest in PV systems.

  9. Phase-staggering control of a series-resonant DC-DC converter with paralleled power modules

    NASA Astrophysics Data System (ADS)

    Klaassens, J. Ben; Moize de Chateleux, Willem L. F. H. A.; van Wesenbeeck, M. P. N.

    1988-04-01

    A method of decreasing the ripple on the output voltage of high-power AC-DC or DC-DC series-resonant converters without increasing the internal converter frequency or the capacity of the energy storage elements is discussed. This improvement is accomplished by subdividing the converter into two or more series-resonant power modules operated with a constant relative phase shift (phase-staggering control). The method of eliminating the harmonic components in the input and output currents of the conversion system, without increasing the internal pulse frequency, is justified by Fourier analysis of the current waveforms. The frequency spectra of the source and output waveforms for the continuous and discontinuous resonant current mode are shifted to higher frequency ranges, as computations show for both one single module and multiple paralleled modules. Inadequacies in the phase-staggering control method applied to series-resonant converters are indicated in relation to the dominant harmonic component, in particular for two modules and supported by experimentally acquired waveforms. High-frequency current components to the source and to the load are reduced, resulting in smaller input and output filters. This improves the resolution of the control of the flow of energy from the source to the load, resulting in a faster system response.

  10. Demonstration of reconfigurable joint orbital angular momentum mode and space switching.

    PubMed

    Liu, Jun; Wang, Jian

    2016-11-21

    We propose and demonstrate space-selective switch functions employing orbital angular momentum (OAM) modes in the space domain for switching network. One is the switching among different OAM modes having different spatial phase structures, called OAM mode switching. The other is the switching among different space locations, called space switching. The switching operation mechanism relies on linear optics. Reconfigurable 4 × 4 OAM mode switching, space switching, and joint OAM mode and space switching fabric using a single spatial light modulator (SLM) are all demonstrated in the experiment. In addition, the presented OAM-incorporated space-selective switch might be further extended to N × N joint OAM mode and space switching with fast response, scalability, cascading ability and compability to facilitate robust switching applications.

  11. Demonstration of reconfigurable joint orbital angular momentum mode and space switching

    PubMed Central

    Liu, Jun; Wang, Jian

    2016-01-01

    We propose and demonstrate space-selective switch functions employing orbital angular momentum (OAM) modes in the space domain for switching network. One is the switching among different OAM modes having different spatial phase structures, called OAM mode switching. The other is the switching among different space locations, called space switching. The switching operation mechanism relies on linear optics. Reconfigurable 4 × 4 OAM mode switching, space switching, and joint OAM mode and space switching fabric using a single spatial light modulator (SLM) are all demonstrated in the experiment. In addition, the presented OAM-incorporated space-selective switch might be further extended to N × N joint OAM mode and space switching with fast response, scalability, cascading ability and compability to facilitate robust switching applications. PMID:27869133

  12. New mode switching algorithm for the JPL 70-meter antenna servo controller

    NASA Technical Reports Server (NTRS)

    Nickerson, J. A.

    1988-01-01

    The design of control mode switching algorithms and logic for JPL's 70 m antenna servo controller are described. The old control mode switching logic was reviewed and perturbation problems were identified. Design approaches for mode switching are presented and the final design is described. Simulations used to compare old and new mode switching algorithms and logic show that the new mode switching techniques will significantly reduce perturbation problems.

  13. Real-Time Implementation of a Fuzzy Logic Controller for DC-DC Switching Converters

    DTIC Science & Technology

    2007-11-02

    studies, it will be observed that, the proposed fuzzy controller maintains the output voltage at the desired 5V with slight overshoot during each...537-546, May 1997. [3] H. Sira -Ramirez, “Design of P-I controllers for DC-to-DC power supplies via extended linearization,” Int. J. Control, vol. 51...Technology, vol. 7, pp. 230-237, Mar. 1999. [5] G. Escobar, R. Ortega, H. Sira -Ramirez, J.P. Vilain and I. Zein, “An experimental comparison of several

  14. Hybrid DC/DC Converter for SAR Antenna Power Supply Unit

    NASA Astrophysics Data System (ADS)

    Calcatterra, Paolo; Galantini, Paolo; Scorzafava, Edmondo; Sagnelli, Salvatore; Benettin, Piero

    2014-08-01

    When distributed power supply is mandatory to provide full functional redundancy in a SAR application, a compact design to minimize size and weight became the main driver of the system.In this context a single hermetic DC/DC converter, including magnetic components, has been made in thick-film Hybrid technology.It is designed for state of the art electrical performance, minimum mass and size, maximum reliability for SAR application, where each transmitter / receiver module is powered by one dedicated DC/DC converterIt is characterised by a very simplified design approach to get high reliability and repeatability for large scale production.The Hybrid uses a standard thick film multilayer technology, currently in use for military and Space application.A few passive components are placed outside the Hybrid according to desired Conducted Emission / Susceptibility performance requirements (input and output filters).The Hybrid is manufactured with multilayer ceramic substrate with ad-hoc solution to manage thermal and cross talk signal issues.The trimming of the PSU is via laser active trimming performed during Hybrid manufacturing. No further trimming is needed.The process control is performed according to MIL PRF 38534.The Hybrid is manufactured according ECSS-Q-ST-60- 05C.

  15. Thermoelectric-Generator-Based DC-DC Conversion Networks for Automotive Applications

    NASA Astrophysics Data System (ADS)

    Li, Molan; Xu, Shaohui; Chen, Qiang; Zheng, Li-Rong

    2011-05-01

    Maximizing electrical energy generation through waste heat recovery is one of the modern research questions within automotive applications of thermoelectric (TE) technologies. This paper proposes a novel concept of distributed multisection multilevel DC-DC conversion networks based on thermoelectric generators (TEGs) for automotive applications. The concept incorporates a bottom-up design approach to collect, convert, and manage vehicle waste heat efficiently. Several state-of-the-art thermoelectric materials are analyzed for the purpose of power generation at each waste heat harvesting location on a vehicle. Optimal materials and TE couple configurations are suggested. Moreover, a comparison of prevailing DC-DC conversion techniques was made with respect to applications at each conversion level within the network. Furthermore, higher-level design considerations are discussed according to system specifications. Finally, a case study is performed to compare the performance of the proposed network and a traditional single-stage system. The results show that the proposed network enhances the system conversion efficiency by up to 400%.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Two-mode interference photonic switch for WDM communications

    NASA Astrophysics Data System (ADS)

    Li, Baojun; Chua, Soo-Jin

    2002-07-01

    A two-mode interference photonic switch with high carrier injection has been designed and fabricated based on free-carrier plasma dispersion effect. It consists of an input Y-branch single-mode ridge waveguide, a two-mode waveguide coupling section, and an output Y-branch single-mode ridge waveguide. The boron doped silicon-germanium material was grown by molecular beam epitaxy and the devices were fabricated by using standard silicon technology. The ridge waveguides were formed by reactive ion etching technique and the input and output facets of the waveguides were ground and polished by a mechanical method. The switch was characterized by using a 1310 nm InGaAsP/InP hetero-structure laser diode. Its insertion loss and On-state crosstalk were measured to be 2.74 and -15.5 dB, respectively, at a total switching current of 110 mA. The switching time is 180 ns and the fastest switching time is up to 30 ns.

  18. rf mode switching in a relativistic magnetron with diffraction output

    SciTech Connect

    Liu Meiqin; Michel, Cedric; Prasad, Sarita; Fuks, Mikhail I.; Schamiloglu, Edl; Liu Chunliang

    2010-12-20

    The relativistic magnetron with diffraction output (RMDO) has demonstrated nearly 70% efficiency in recent simulations. This letter reports a rapid mode switching technique in the RMDO using a low power, short-pulse, external single frequency signal. The MAGIC electromagnetic finite-difference-time-domain particle-in-cell code used in simulations demonstrated that an input signal of 300 kW is sufficient to switch neighboring modes in a gigawatt output power A6 RMDO with a transparent cathode, whereas for the original A6 magnetron configuration with radial extraction driven by a transparent cathode 30 MW is required. This frequency agility adds additional versatility to this high power microwave source.

  19. Combustion mode switching with a turbocharged/supercharged engine

    SciTech Connect

    Mond, Alan; Jiang, Li

    2015-09-22

    A method for switching between low- and high-dilution combustion modes in an internal combustion engine having an intake passage with an exhaust-driven turbocharger, a crankshaft-driven positive displacement supercharger downstream of the turbocharger and having variable boost controllable with a supercharger bypass valve, and a throttle valve downstream of the supercharger. The current combustion mode and mass air flow are determined. A switch to the target combustion mode is commanded when an operating condition falls within a range of predetermined operating conditions. A target mass air flow to achieve a target air-fuel ratio corresponding to the current operating condition and the target combustion mode is determined. The degree of opening of the supercharger bypass valve and the throttle valve are controlled to achieve the target mass air flow. The amount of residual exhaust gas is manipulated.

  20. Temperature switching of cavity modes in InN microcrystals

    SciTech Connect

    Kazanov, D. R. Kaibyshev, V. H.; Davydov, V. Yu.; Smirnov, A. N.; Jmerik, V. N.; Kuznetsova, N. V.; Kopiev, P. S.; Ivanov, S. V.; Shubina, T. V.

    2015-11-15

    InN optical cavities supporting low-order whispering-gallery modes up to room temperature are formed by molecular-beam epitaxy on patterned substrates. The observed switching of the mode type with increasing temperature is explained in terms of changes in the optical parameters due to a shift of the absorption edge and modification of its shape. Modeling taking into account a variation in the refractive index reproduces the typical distributions of the electromagnetic-field intensity in the cavities.

  1. Development of Compact Variable-Voltage, Bi-Directional 100KW DC-DC Converter

    DTIC Science & Technology

    2007-06-01

    increase operation frequency, decrease converter weight and size, including (i) a novel yet simple approach developed to achieve zero- voltage soft...inductor current are plotted in a 100kW operating condition. It can be seen that when the switch turns on, its drain voltage is zero and the...output voltage fluctuation. Figure 9 shows the experimental output voltage and current and inductor current waveforms under boost mode operation when

  2. Low-temperature operation of a Buck DC/DC converter

    NASA Technical Reports Server (NTRS)

    Ray, Biswajit; Gerber, Scott S.; Patterson, Richard L.; Myers, Ira T.

    1995-01-01

    Low-temperature (77 K) operation of a 42/28 V, 175 W, 50 kHz PWM Buck DC/DC converter designed with commercially available components is reported. Overall, the converter losses decreased at 77 K compared to room temperature operation. A full-load efficiency of 97 percent was recorded at liquid-nitrogen temperature, compared to 95.8 percent at room temperature. Power MOSFET operation improved significantly where as the output rectifier operation deteriorated at low-temperature. The performance of the output filter inductor and capacitor did not change significantly at 77 K compared to room temperature performance. It is possible to achieve high-density and high efficiency power conversion at low-temperatures due to improved electronic, electrical and thermal properties of materials.

  3. Some results regarding stability of photovoltaic maximum-power-point tracking dc-dc converters

    NASA Astrophysics Data System (ADS)

    Schaefer, John F.

    An analytical investigation of a class of photovoltaic (PV) maximum-power-point tracking dc-dc converters has yielded basic results relative to the stability of such devices. Necessary and sufficient conditions for stable operation are derived, and design tools are given. Specific results have been obtained for arbitrary PV arrays driving converters powering resistive loads and batteries. The analytical techniques are applicable to inverters, also. Portions of the theoretical results have been verified in operational devices: a 1500 watt unit has driven a 1-horsepower, 90-volt dc motor powering a water pump jack for over one year. Prior to modification shortly after initial installation, the unit exhibited instability at low levels of irradiance, as predicted by the theory. Two examples are provided.

  4. Practical Design Guidelines of qZSI Based Step-Up DC/DC Converter

    NASA Astrophysics Data System (ADS)

    Zakis, Janis; Vinnikov, Dmitri; Roasto, Indrek; Jalakas, Tanel

    2010-01-01

    This paper presents some design guidelines for a new voltage fed step-up DC/DC isolated converter. The most significant advantage of proposed converter is voltage buck-boost operation on single stage. The most promising application for proposed converter is in the field of distributed power generation e.g. fuel cells or photovoltaic. The most sensitive issues - such as power losses caused by high currents in the input side of converter and high transient overvoltages across the inverter bridge caused by stray inductances were discussed and solved. The proposals and recommendations to overcome these issues are given in the paper. The Selection and design guidelines of converter elements are proposed and explained. The prototype of proposed converter was built and experimentally tested. Some results are presented and evaluated.

  5. Low Temperature Performance of High Power Density DC/DC Converter Modules

    NASA Technical Reports Server (NTRS)

    Elbuluk, Malik E.; Hammond, Ahmad; Gerber, Scott; Patterson, Richard L.; Overton, Eric

    2001-01-01

    In this paper, two second-generation high power density DC/DC converter modules have been evaluated at low operating temperatures. The power rating of one converter (Module 1) was specified at 150 W with an input voltage range of 36 to 75 V and output voltage of 12 V. The other converter (Module 2) was specified at 100 W with the same input voltage range and an output voltage of 3.3 V. The converter modules were evaluated in terms of their performance as a function of operating temperature in the range of 25 to -140 C. The experimental procedures along with the experimental data obtained are presented and discussed in this paper.

  6. DC-DC converters in 0.35μm CMOS technology

    NASA Astrophysics Data System (ADS)

    Michelis, S.; Allongue, B.; Blanchot, G.; Faccio, F.; Fuentes, C.; Orlandi, S.; Saggini, S.; Cengarle, S.; Ongaro, F.

    2012-01-01

    In view of the upgrade of the LHC experiments, we are developing custom DC/DC converters for a more efficient power distribution scheme. A new prototype have been integrated in ASICs in the selected 0.35μm commercial high voltage technology that has been successfully tested for all radiation effects: TID, displacement damage and Single Event Burnout. This converter has been optimized for high efficiency and improved radiation tolerance. Amongst the new features the most relevant are the presence of internal linear regulators, protection circuits with a state-machine and a new pinout for a modified assembly in package in order to reduce conductive losses. This paper illustrates the design of the prototype followed by functional and radiation tests.

  7. All-fiber optical mode switching based on cascaded mode selective couplers for short-reach MDM networks

    NASA Astrophysics Data System (ADS)

    Ren, Fang; Li, Juhao; Wu, Zhongying; Yu, Jinyi; Mo, Qi; Wang, Jianping; He, Yongqi; Chen, Zhangyuan; Li, Zhengbin

    2017-04-01

    We propose and experimentally demonstrate an all-fiber optical mode switching structure supporting independent switching, exchanging, adding, and dropping functionalities in which each mode can be switched individually. The mode switching structure consists of cascaded mode selective couplers (MSCs) capable of exciting and selecting specific higher order modes in few-mode fibers with high efficiency and one multiport optical switch routing the independent spatial modes to their destinations. The data carried on three different spatial modes can be switched, exchanged, added, and dropped through this all-fiber structure. For this experimental demonstration, optical on-off-keying (OOK) signals at 10-Gb/s carried on three spatial modes are successfully processed with open and clear eye diagrams. The mode switch exhibits power penalties of less than 3.1 dB after through operation, less than 2.7 dB after exchange operation, less than 2.8 dB after switching operation, and less than 1.6 dB after mode adding and dropping operations at the bit-error rate (BER) of 10-3, while all three channels carried on three spatial modes are simultaneously routed. The proposed structure, compatible with current optical switching networks based on single-mode fibers, can potentially be used to expand the switching scalability in advanced and flexible short-reach mode-division multiplexing-based networks.

  8. 75 FR 446 - In the Matter of Certain DC-DC Controllers and Products; Notice of Investigation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-05

    ... Controllers and Products; Notice of Investigation AGENCY: U.S. International Trade Commission. ACTION... controllers and products containing same by reason of infringement of certain claims of U.S. Patent Nos. 7,315... States after importation of certain DC--DC controllers or products containing the same that infringe one...

  9. A common-gate bootstrapped CMOS rectifier for VHF isolated DC-DC converter

    NASA Astrophysics Data System (ADS)

    Pan, Dongfang; Zhang, Feng; Huang, Lu; Li, Jinliang

    2017-06-01

    A common-gate bootstrapped CMOS rectifier dedicated for VHF (very high frequency) isolated DC-DC converter is proposed. It uses common-gate bootstrapped technique to compensate the power loss due to the threshold voltage, and to solve the reflux problem in the conventional rectifier circuit. As a result, it improves the power conversion efficiency (PCE) and voltage conversion ratio (VCR). The design saves almost 90% of the area compared to a previously reported double capacitor structure. In addition, we compare the previous rectifier with the proposed common-gate bootstrapped rectifier in the case of the same area; simulation results show that the PCE and VCR of the proposed structure are superior to other structures. The proposed common-gate bootstrapped rectifier was fabricated by using CSMC 0.5 μm BCD process. The measured maximum PCE is 86% and VCR achieves 77% at the operating frequency of 20 MHz. The average PCE is about 79% and average VCR achieves 71% in the frequency range of 30-70 MHz. Measured PCE and VCR have been improved compared to previous results.

  10. Lightweight DC-DC Converter with Partial Power Processing and MPPT for a Solar Powered Aircraft

    NASA Astrophysics Data System (ADS)

    Diab-Marzouk, Ahmad

    A lightweight dc-dc partial power processing converter is demonstrated for solar aerospace applications. A system-level model is conceived to determine conformity to payload and target distance objectives, with the Solarship aircraft used as an application example. The concept of partial power processing is utilized to realize a high efficiency lightweight converter that performs Max Peak Power Tracking (MPPT) to transfer power from the aircraft solar array to the high-voltage battery bus. The isolated Cuk is determined to be a suitable converter topology for the application. A small-signal model is derived for control design. The operation of a 400V, 2.7 kW prototype is verified at high frequency (200 kHz), high efficiency (> 98%), small mass (0.604 kg), and uses no electrolytic capacitors. MPPT operation is verified on a 376 V commercial solar installation at The University of Toronto. The prototype serves as an enabling technology for solar aerospace applications.

  11. Performance of a Voltage Step-Up/Step-Down Transformerless DC/DC Converter: Analytical Model

    NASA Astrophysics Data System (ADS)

    Suskis, P.; Rankis, I.

    2012-01-01

    The authors present an analytical model for a voltage step-up/step-down DC/DC converter without transformers. The proposed topology is a combination of classic buck and boost converters in one single circuit but with differing operational principles. The converter is developed for a wind power autonomous supply system equipped with a hydrogen electrolytic tank and a fuel cell for energy stabilization. The main power source of the hydrogen-based autonomous supply system is energized by a synchronous generator operating on permanent magnets and equipped with a diode bridge. The input voltage of the converter in this case varies in the range 0-700 V, while its output DC voltage must be 540 V according to the demand of other parts of the system. To maintain the rated voltage, a special electrical load regulation is introduced. The calculations of the converter, the generator (equipped with a diode bridge) as element of the power system supply joint, and the load replaced by resistance are verified with PSIM software.

  12. Multiphase High-Frequency Isolated DC-DC Converter for Industrial Applications

    NASA Astrophysics Data System (ADS)

    Maurya, Rakesh; Srivastava, S. P.; Agarwal, Pramod

    2014-01-01

    Industrial applications such as welding, plasma cutting, and surface hardening require a large DC current at low voltage. In such applications, the rating of power supply varies from few kilowatts to hundreds of kilowatts. The power supply employs in such applications particularly in arc welding process is expected to operate from open-circuit (no-load) to short-circuit (when the electrode sticks to the workpiece for a short span of time) quickly. In this paper, high-frequency isolated multiphase DC-DC converter is proposed which is well suited for aforementioned applications. Based on mathematical analysis, a simulation study with 5 kW, 5 V/1,000 A proposed model is carried out using Simulink block set and Sim Power System tool box and its performances are evaluated under symmetrical control methods. To verify the simulation results, scaled prototype model of rating 1.5 V/100 A is developed and tested with aforementioned control method under different operating conditions. In comparison with conventional welding power supply employed in many industries, the performance of proposed converter is improved significantly in terms of size and weight, efficiency and dynamic response.

  13. Development of a Novel Bi-Directional Isolated Multiple-Input DC-DC Converter

    SciTech Connect

    Li, H.

    2005-10-24

    There is vital need for a compact, lightweight, and efficient energy-storage system that is both affordable and has an acceptable cycle life for the large-scale production of electric vehicles (EVs) and hybrid electric vehicles (HEVs). Most of the current research employs a battery-storage unit (BU) combined with a fuel cell (FC) stack in order to achieve the operating voltage-current point of maximum efficiency for the FC system. A system block diagram is shown in Fig.1.1. In such a conventional arrangement, the battery is sized to deliver the difference between the energy required by the traction drive and the energy supplied by the FC system. Energy requirements can increase depending on the drive cycle over which the vehicle is expected to operate. Peak-power transients result in an increase of losses and elevated temperatures which result in a decrease in the lifetime of the battery. This research will propose a novel two-input direct current (dc) dc to dc converter to interface an additional energy-storage element, an ultracapacitor (UC), which is shown in Fig.1.2. It will assist the battery during transients to reduce the peak-power requirements of the battery.

  14. Design of piezoelectric transformer for DC/DC converter with stochastic optimization method

    NASA Astrophysics Data System (ADS)

    Vasic, Dejan; Vido, Lionel

    2016-04-01

    Piezoelectric transformers were adopted in recent year due to their many inherent advantages such as safety, no EMI problem, low housing profile, and high power density, etc. The characteristics of the piezoelectric transformers are well known when the load impedance is a pure resistor. However, when piezoelectric transformers are used in AC/DC or DC/DC converters, there are non-linear electronic circuits connected before and after the transformer. Consequently, the output load is variable and due to the output capacitance of the transformer the optimal working point change. This paper starts from modeling a piezoelectric transformer connected to a full wave rectifier in order to discuss the design constraints and configuration of the transformer. The optimization method adopted here use the MOPSO algorithm (Multiple Objective Particle Swarm Optimization). We start with the formulation of the objective function and constraints; then the results give different sizes of the transformer and the characteristics. In other word, this method is looking for a best size of the transformer for optimal efficiency condition that is suitable for variable load. Furthermore, the size and the efficiency are found to be a trade-off. This paper proposes the completed design procedure to find the minimum size of PT in need. The completed design procedure is discussed by a given specification. The PT derived from the proposed design procedure can guarantee both good efficiency and enough range for load variation.

  15. On the possibility of a new passively Q-switched laser operation mode with periodic wavelength switching

    SciTech Connect

    Fedorov, A V; Fomichev, A A; Doroshenko, M E

    2015-06-30

    The possibility of cw-pumped passively Q-switched laser operation has been examined theoretically. Also, we have proposed laser operation mode in which the output wavelength automatically switches between two values without any changes in cavity parameters. Using numerical simulation and an Er:YAG laser with a Co:ZnSe passive Q-switch as an example, we have found parameters that ensure such operation mode. (lasers)

  16. Diode pumped Q-switched and mode locked lasers

    NASA Astrophysics Data System (ADS)

    Jabczyński, Jan K.; Żendzian, Waldemar; Kwiatkowski, Jacek

    2005-09-01

    The simultaneous Q-Switching and Mode Locking (QML) regime provides the generation of relatively high peak power picosecond pulses train with energies of a few μJ each in a simple resonator. The critical review of QML methods and results including our investigations is given in the first part of presentation. The application of several types of saturable crystalline absorbers (Cr4+:YAG, V3+:YAG, LiF, GaAs) leads to chaotic, partial QML effect, with less than 100% modulation depth in principle. The fully modulated efficient QML laser was demonstrated in the next part. The acousto-optic cell playing a double role of Q-switch and Mode Locker was located near flat output coupler. The two folding mirrors were mounted on the translation stages for matching the resonance frequency of the cavity to the radio frequency of acousto-optic modulator. The QML pulses with envelope durations of 100-150 ns and 100% modulation depth were observed for wide range of pump powers and repetition rates. In the preliminary experiments up to 3 W of output average power, 100μJ of the envelope energy, having approximately 5-8 mode locked pulses were achieved.

  17. A High Efficiency DC-DC Converter Topology Suitable for Distributed Large Commercial and Utility Scale PV Systems

    SciTech Connect

    Agamy, Mohammed S; Harfman-Todorovic, Maja; Elasser, Ahmed; Steigerwald, Robert L; Sabate, Juan A; Chi, Song; McCann, Adam J; Zhang, Li; Mueller, Frank

    2012-09-01

    In this paper a DC-DC power converter for distributed photovoltaic plant architectures is presented. The proposed converter has the advantages of simplicity, high efficiency, and low cost. High efficiency is achieved by having a portion of the input PV power directly fed forward to the output without being processed by the converter. The operation of this converter also allows for a simplified maximum power point tracker design using fewer measurements

  18. An Interleaved Reduced-Component-Count Multivoltage Bus DC/DC Converter for Fuel Cell Powered Electric Vehicle Applications

    SciTech Connect

    Tang, Lixin; Su, Gui-Jia

    2008-01-01

    An interleaved reduced-component-count dc/dc converter is proposed for power management in fuel cell powered vehicles with a multivoltage electric net. The converter is based on a simplified topology and can handle more power with less ripple current, therefore reducing the capacitor requirements, making it more suited for fuel cell powered vehicles in the near future. A prototype rated at 4.3 kW was built and tested to verify the proposed topology.

  19. Dynamically encircling an exceptional point for asymmetric mode switching

    NASA Astrophysics Data System (ADS)

    Doppler, Jörg; Mailybaev, Alexei A.; Böhm, Julian; Kuhl, Ulrich; Girschik, Adrian; Libisch, Florian; Milburn, Thomas J.; Rabl, Peter; Moiseyev, Nimrod; Rotter, Stefan

    2016-09-01

    Physical systems with loss or gain have resonant modes that decay or grow exponentially with time. Whenever two such modes coalesce both in their resonant frequency and their rate of decay or growth, an ‘exceptional point’ occurs, giving rise to fascinating phenomena that defy our physical intuition. Particularly intriguing behaviour is predicted to appear when an exceptional point is encircled sufficiently slowly, such as a state-flip or the accumulation of a geometric phase. The topological structure of exceptional points has been experimentally explored, but a full dynamical encircling of such a point and the associated breakdown of adiabaticity have remained out of reach of measurement. Here we demonstrate that a dynamical encircling of an exceptional point is analogous to the scattering through a two-mode waveguide with suitably designed boundaries and losses. We present experimental results from a corresponding waveguide structure that steers incoming waves around an exceptional point during the transmission process. In this way, mode transitions are induced that transform this device into a robust and asymmetric switch between different waveguide modes. This work will enable the exploration of exceptional point physics in system control and state transfer schemes at the crossroads between fundamental research and practical applications.

  20. Mode switching in volcanic seismicity: El Hierro 2011-2013

    NASA Astrophysics Data System (ADS)

    Roberts, Nick S.; Bell, Andrew F.; Main, Ian G.

    2016-05-01

    The Gutenberg-Richter b value is commonly used in volcanic eruption forecasting to infer material or mechanical properties from earthquake distributions. Such studies typically analyze discrete time windows or phases, but the choice of such windows is subjective and can introduce significant bias. Here we minimize this sample bias by iteratively sampling catalogs with randomly chosen windows and then stack the resulting probability density functions for the estimated b>˜ value to determine a net probability density function. We examine data from the El Hierro seismic catalog during a period of unrest in 2011-2013 and demonstrate clear multimodal behavior. Individual modes are relatively stable in time, but the most probable b>˜ value intermittently switches between modes, one of which is similar to that of tectonic seismicity. Multimodality is primarily associated with intermittent activation and cessation of activity in different parts of the volcanic system rather than with respect to any systematic inferred underlying process.

  1. High Power Switching Transistor

    NASA Technical Reports Server (NTRS)

    Hower, P. L.; Kao, Y. C.; Carnahan, D. C.

    1983-01-01

    Improved switching transistors handle 400-A peak currents and up to 1,200 V. Using large diameter silicon wafers with twice effective area as D60T, form basis for D7 family of power switching transistors. Package includes npn wafer, emitter preform, and base-contact insert. Applications are: 25to 50-kilowatt high-frequency dc/dc inverters, VSCF converters, and motor controllers for electrical vehicles.

  2. On Application of Model Predictive Control to Power Converter with Switching

    NASA Astrophysics Data System (ADS)

    Zanma, Tadanao; Fukuta, Junichi; Doki, Shinji; Ishida, Muneaki; Okuma, Shigeru; Matsumoto, Takashi; Nishimori, Eiji

    This paper concerns a DC-DC converter control. In DC-DC converters, there exist both continuous components such as inductance, conductance and resistance and discrete ones, IGBT and MOSFET as semiconductor switching elements. Such a system can be regarded as a hybrid dynamical system. Thus, this paper presents a dc-dc control technique based on the model predictive control. Specifically, a case in which the load of the dc-dc converter changes from active to sleep is considered. In the case, a control method which makes the output voltage follow to the reference quickly in transition, and the switching frequency be constant in steady state. In addition, in applying the model predictive control to power electronics circuits, the switching characteristic of the device and the restriction condition for protection are also considered. The effectiveness of the proposed method is illustrated by comparing a conventional method through some simulation results.

  3. 275 C Downhole Switched-Mode Power Supply

    SciTech Connect

    Chris Hutchens; Vijay Madhuravasal

    2008-08-31

    A vee-square (V2) control based controller IC is developed for a switch mode power supply capable of operating at extreme temperature/harsh environment conditions. A buck type regulator with silicon carbide power junction field effect transistors (JFET) as power devices is used to analyze the performance of controller. Special emphases are made on the analog sub-blocks--voltage reference, operational transconductance amplifier and comparator as individual building blocks. Transformer coupled gate drives and high temperature operable magnetic cores and capacitors are identified and tested for use in the design. Conventional ceramic chip packaging of ICs combined with lead carrier type mounting of passive filter components is introduced for hybrid packaging of the complete product. The developed SMPS is anticipated to support the operation of down-hole microcontrollers and other electronics devices that require low/medium power filtered dc inputs over an operating temperature of 275 C.

  4. Pretilt Angle Dependence of the Switching Behavior in the Intrinsic Half-V-Shaped Switching Ferroelectric Liquid Crystal Mode

    NASA Astrophysics Data System (ADS)

    Asao, Yasufumi; Togano, Takeshi

    2003-07-01

    The intrinsic half-V-shaped switching ferroelectric liquid crystal mode (iHV-FLC mode) which is obtained from a material with isotropic (Iso.), cholesteric (Ch) and chiral smectic C (SmC*) phase transition sequences can easily yield excellent moving pictures. There are very few reports of liquid crystal (LC) molecular alignment during the Ch-SmC* phase transition sequence although it is important to clarify the molecular alignment and switching behavior in order to improve device characteristics such as the contrast ratio. We have conducted a detailed observation of the switching behavior of a cell with a striped texture and examined the pretilt angle dependence of the alignment state.

  5. Switched control of vehicle suspension based on motion-mode detection

    NASA Astrophysics Data System (ADS)

    Du, Haiping; Zhang, Nong; Wang, Lifu

    2014-01-01

    This paper presents a study on switched control of vehicle suspension based on motion-mode detection. This control strategy can be potentially implemented via the interconnected suspension such as hydraulically interconnected suspension by actively switching its interconnection configuration in terms of the dominant vehicle body motion-mode. The design of the switched control law is developed focusing on three vehicle body motion-modes: bounce, pitch, and roll. At first, an H∞ optimal controller will be designed for each motion-mode with the use of a common quadratic Lyapunov function, which guarantees the stability of the switched system under arbitrary switching functions. Then, a motion-mode detection method based on the calculation of the motion-mode energy is introduced. And then, the possible implementation of the control system in practice is discussed. Finally, numerical simulations are used to validate the proposed study.

  6. An Approach to Average Modeling and Simulation of Switch-Mode Systems

    ERIC Educational Resources Information Center

    Abramovitz, A.

    2011-01-01

    This paper suggests a pedagogical approach to teaching the subject of average modeling of PWM switch-mode power electronics systems through simulation by general-purpose electronic circuit simulators. The paper discusses the derivation of PSPICE/ORCAD-compatible average models of the switch-mode power stages, their software implementation, and…

  7. An Approach to Average Modeling and Simulation of Switch-Mode Systems

    ERIC Educational Resources Information Center

    Abramovitz, A.

    2011-01-01

    This paper suggests a pedagogical approach to teaching the subject of average modeling of PWM switch-mode power electronics systems through simulation by general-purpose electronic circuit simulators. The paper discusses the derivation of PSPICE/ORCAD-compatible average models of the switch-mode power stages, their software implementation, and…

  8. Switching phenomena between several out of phase modes on coupled chemical oscillators

    NASA Astrophysics Data System (ADS)

    Mitani, H.; Nishiyama, N.; Jinguji, R.

    2000-06-01

    Arrays of cation-exchanged beads loaded with ferroin immersed in the Belousov-Zhabotinsky (BZ) reaction mixture, show, not only a phase propagating mode among the beads, but also a switching among such the several modes. A modified Brüsserator equation leads an equation set of phase deviations of these beads which includes a dynamical matrix; it can explain the switchings. .

  9. Switch failure diagnosis based on inductor current observation for boost converters

    NASA Astrophysics Data System (ADS)

    Jamshidpour, E.; Poure, P.; Saadate, S.

    2016-09-01

    Face to the growing number of applications using DC-DC power converters, the improvement of their reliability is subject to an increasing number of studies. Especially in safety critical applications, designing fault-tolerant converters is becoming mandatory. In this paper, a switch fault-tolerant DC-DC converter is studied. First, some of the fastest Fault Detection Algorithms (FDAs) are recalled. Then, a fast switch FDA is proposed which can detect both types of failures; open circuit fault as well as short circuit fault can be detected in less than one switching period. Second, a fault-tolerant converter which can be reconfigured under those types of fault is introduced. Hardware-In-the-Loop (HIL) results and experimental validations are given to verify the validity of the proposed switch fault-tolerant approach in the case of a single switch DC-DC boost converter with one redundant switch.

  10. Transportation control of microfluidic particles using mode switching between surface acoustic waves and plate waves

    NASA Astrophysics Data System (ADS)

    Hsu, Jin-Chen; Huang, Yeo-Wei; Hsu, Chih-Hsun

    2017-07-01

    In this study, we report the numerical and experimental results of guided acoustic mode switching between surface and plate acoustic waves (SAWs and PAWs) for manipulating microparticles suspended in a microfluidic channel. Numerical results show switchable acoustic pressure and acoustic radiation force fields for controlling particle motion in the microfluidic channel by acoustic mode switching. Acoustic mode switching can be achieved by designing an acoustic-wave device and by changing the frequencies of the input electrical signal. The working mechanisms of acoustic-mode-switchable manipulation are revealed. On the basis of numerical prediction, the feasibility of a mode-switchable acoustic microfluidic device is experimentally demonstrated, and the actuation of suspended microparticles using SAWs and PAWs is achieved. We note that this study provides access to mode-switching acoustophoresis.

  11. Switching deformation mode during natural faulting in Carrara marbles.

    NASA Astrophysics Data System (ADS)

    Molli, Giancarlo

    2010-05-01

    A study on meso- and microstructural features of a high angle normal fault observed in the Alpi Apuane NW Tuscany (Italy) is presented to document switching in the deformation mode during different evolutionary stages of a fault zone growth in naturally deformed Carrara marble. The studied fault was formed at c.3 Km of depth and belongs to structures related to the most recent deformation history of the Alpi Apuane metamorphic core (from c.4 Ma until now, Fellin et al. 2007; Molli, 2008). On the basis of deformation mechanisms and their chronology interpreted from cross-cutting relationships, different stages of the fault zone evolution have been recognized. An early stage of deformation (stage 1) was associated with extensional and shear veins now observable in both hangingwall and footwall blocks as part of the deformation zone developed at decameter-scale. Geochemical data indicate vein-development in a locally closed system where a "stationary" fluid phase migrates over meter scale distances (Molli et al., in press). During stage 2, a localization of the deformation, possibly in precursory coarse grained calcite/quartz shear veins of stage 1, took place. During this second stage crystal-plastic deformation affected areas at the head and along the hanging wall rim of fractures accommodating fault tip distorsions in a way recalling the mode-II geometry of stable crack propagation (Atkinson, 1987; Vermilye and Scholtz, 1993; Kim et al., 2004). Following pervasive cataclasis (stage 3) characterizes a plurimeter-wide dilational jog between two non-parallel main slip surfaces with brecciation and far-derived fluids channelling leading to significant geochemical alteration of the fault rocks with respect to the protolith (Molli et al., in press). Cataclastic deformation produced a grain size refinement and a decimetric thick fault core asymmetrically bounded by the upper main slip surface. Deformation was then localized within ultracataclasite of the fault core where

  12. A study of DC-DC converters with MCT's for arcjet power supplies

    NASA Technical Reports Server (NTRS)

    Stuart, Thomas A.

    1994-01-01

    Many arcjet DC power supplies use PWM full bridge converters with large arrays of parallel FET's. This report investigates an alternative supply using a variable frequency series resonant converter with small arrays of parallel MCT's (metal oxide semiconductor controlled thyristors). The reasons for this approach are to: increase reliability by reducing the number of switching devices; and decrease the surface mounting area of the switching arrays. The variable frequency series resonant approach is used because the relatively slow switching speed of the MCT precludes the use of PWM. The 10 kW converter operated satisfactorily with an efficiency of over 91 percent. Test results indicate this efficiency could be increased further by additional optimization of the series resonant inductor.

  13. Experience from design, prototyping and production of a DC-DC conversion powering scheme for the CMS Phase-1 Pixel Upgrade

    NASA Astrophysics Data System (ADS)

    Feld, Lutz; Karpinski, Waclaw; Klein, Katja; Lipinski, Martin; Preuten, Marius; Rauch, Max; Schmitz, Stefan; Wlochal, Michael

    2017-02-01

    The CMS pixel detector will be replaced during the technical stop 2016/2017. To allow the new pixel detector to be powered with the legacy cable plant and power supplies, a novel powering scheme based on DC-DC conversion will be employed. After the successful conclusion of an extensive development and prototyping phase, mass production of 1800 DC-DC converters as well as motherboards and other power PCBs has now been completed. This contribution reviews the lessons learned from the development of the power system for the Phase-1 pixel detector, and summarizes the experience gained from the production phase.

  14. Simultaneous Q-switching and mode-locking in the CW Nd:YAG laser

    NASA Technical Reports Server (NTRS)

    Kuizenga, D. J.; Phillion, D. W.; Siegman, A. E.; Lund, T.

    1973-01-01

    The theory of transient mode-locking for an active modulator in a laser with a homogeneously broadened line is presented. The theory is applied to simultaneously Q-switched and mode-locked Nd:YAG lasers and good agreement between theory and experiment is obtained. The main conclusion is that under usual Q-switched operating conditions the mode-locking process does not have sufficient time to build up to steady-state conditions. We also present a method to overcome this problem by allowing the laser to prelase before the Q-switch is opened. Mode-locked pulses whose width approaches the steady-state value are obtained. The transient mode-locking theory presented here also applies to actively mode-locking TEA CO2 lasers and to other types of simultaneously pulsed and mode-locked lasers.

  15. Isolated and soft-switched power converter

    DOEpatents

    Peng, Fang Zheng; Adams, Donald Joe

    2002-01-01

    An isolated and soft-switched power converter is used for DC/DC and DC/DC/AC power conversion. The power converter includes two resonant tank circuits coupled back-to-back through an isolation transformer. Each resonant tank circuit includes a pair of resonant capacitors connected in series as a resonant leg, a pair of tank capacitors connected in series as a tank leg, and a pair of switching devices with anti-parallel clamping diodes coupled in series as resonant switches and clamping devices for the resonant leg. The power converter is well suited for DC/DC and DC/DC/AC power conversion applications in which high-voltage isolation, DC to DC voltage boost, bidirectional power flow, and a minimal number of conventional switching components are important design objectives. For example, the power converter is especially well suited to electric vehicle applications and load-side electric generation and storage systems, and other applications in which these objectives are important. The power converter may be used for many different applications, including electric vehicles, hybrid combustion/electric vehicles, fuel-cell powered vehicles with low-voltage starting, remote power sources utilizing low-voltage DC power sources, such as photovoltaics and others, electric power backup systems, and load-side electric storage and generation systems.

  16. Simulating and Testing a DC-DC Half-Bridge SLR Converter

    DTIC Science & Technology

    2013-06-01

    bias while the switch is on. Afterwards, DSV does not return immediately to D DV ; the diode recovery creates high frequency oscillations . H...34 ~ ~ FAIRCHIL..C SEMICONDUCTOR* 65 N-CHANNEL POWER MOSFET IRFM120A Fig 12. Gate Charge Test Circuit & Waveform 1 ’"" n -r Same Type as DUf

  17. Optically controllable dual-mode switching in single-mode Fabry-Pérot laser diode subject to one side-mode feedback and external single mode injection

    NASA Astrophysics Data System (ADS)

    Wu, Jian-Wei; Won, Yong Hyub

    2017-06-01

    In this paper, broadly tunable dual-mode lasing system is presented and demonstrated based on single-mode Fabry-Pérot laser diode subject to the feedback of one side mode amplified by an erbium-doped fiber amplifier in the external feedback cavity. The spacing between two resonance modes in output lasing spectrum is broadly tuned by introducing differently amplified side mode into the single-mode laser via the external cavity consisted of amplifier, filter, and polarization controller so that two difference frequencies of 1 THz and 0.6 THz are given to display the tunable behavior of dual-mode emission in this work. Therefore, under an external injection mode into the laser condition, the power dependent injection locking and optical bistability of generated dual-mode emission are discussed in detail. At different wavelength detunings, the emitted two resonance modes including the dominant and feedback modes are switched to on- or off-state by selecting proper high-low power level of the external injection mode. As a consequence, the maximum value of achieved dual-mode on-off ratio is as high as up to 45 dB.

  18. Maximum power point tracking for photovoltaic applications by using two-level DC/DC boost converter

    NASA Astrophysics Data System (ADS)

    Moamaei, Parvin

    Recently, photovoltaic (PV) generation is becoming increasingly popular in industrial applications. As a renewable and alternative source of energy they feature superior characteristics such as being clean and silent along with less maintenance problems compared to other sources of the energy. In PV generation, employing a Maximum Power Point Tracking (MPPT) method is essential to obtain the maximum available solar energy. Among several proposed MPPT techniques, the Perturbation and Observation (P&O;) and Model Predictive Control (MPC) methods are adopted in this work. The components of the MPPT control system which are P&O; and MPC algorithms, PV module and high gain DC-DC boost converter are simulated in MATLAB Simulink. They are evaluated theoretically under rapidly and slowly changing of solar irradiation and temperature and their performance is shown by the simulation results, finally a comprehensive comparison is presented.

  19. Fuel Cell/Electric Double Layer Capacitor Hybrid Power Source Using a Multi-port Bidirectional DC-DC Converter

    NASA Astrophysics Data System (ADS)

    Katayama, Noboru; Kogoshi, Sumio

    A fuel cell/electric double layer capacitor hybrid power source using a multi-port bidirectional DC-DC converter has been developed to reduce load variations for the purpose of extending fuel cell life. The proposed converter operates to maintain the fuel cell current, load voltage and bus voltage at constant values with a digital signal processor. The effect of the proposed converter is evaluated. The charging or discharging current of the EDLC rapidly changes along with step loading, and the voltage and current of the fuel cell are maintained at the constant values. Short-time transient responses show that the fuel cell current ripples 0.35 A at 1 A load change in 6 ms.

  20. Anticipatory processes in brain state switching - evidence from a novel cued-switching task implicating default mode and salience networks.

    PubMed

    Sidlauskaite, Justina; Wiersema, Jan R; Roeyers, Herbert; Krebs, Ruth M; Vassena, Eliana; Fias, Wim; Brass, Marcel; Achten, Eric; Sonuga-Barke, Edmund

    2014-09-01

    The default mode network (DMN) is the core brain system supporting internally oriented cognition. The ability to attenuate the DMN when switching to externally oriented processing is a prerequisite for effective performance and adaptive self-regulation. Right anterior insula (rAI), a core hub of the salience network (SN), has been proposed to control the switching from DMN to task-relevant brain networks. Little is currently known about the extent of anticipatory processes subserved by DMN and SN during switching. We investigated anticipatory DMN and SN modulation using a novel cued-switching task of between-state (rest-to-task/task-to-rest) and within-state (task-to-task) transitions. Twenty healthy adults performed the task implemented in an event-related functional magnetic resonance imaging (fMRI) design. Increases in activity were observed in the DMN regions in response to cues signalling upcoming rest. DMN attenuation was observed for rest-to-task switch cues. Obversely, DMN was up-regulated by task-to-rest cues. The strongest rAI response was observed to rest-to-task switch cues. Task-to-task switch cues elicited smaller rAI activation, whereas no significant rAI activation occurred for task-to-rest switches. Our data provide the first evidence that DMN modulation occurs rapidly and can be elicited by short duration cues signalling rest- and task-related state switches. The role of rAI appears to be limited to certain switch types - those implicating transition from a resting state and to tasks involving active cognitive engagement. Copyright © 2014 Elsevier Inc. All rights reserved.

  1. A Low-Cost Soft-Switched DC/DC Converter for Solid-Oxide Fuel Cells

    SciTech Connect

    Jason Lai

    2009-03-03

    A highly efficient DC to DC converter has been developed for low-voltage high-current solid oxide fuel cells. The newly developed 'V6' converter resembles what has been done in internal combustion engine that split into multiple cylinders to increase the output capacity without having to increase individual cell size and to smooth out the torque with interleaving operation. The development was started with topology overview to ensure that all the DC to DC converter circuits were included in the study. Efficiency models for different circuit topologies were established, and computer simulations were performed to determine the best candidate converter circuit. Through design optimization including topology selection, device selection, magnetic component design, thermal design, and digital controller design, a bench prototype rated 5-kW, with 20 to 50V input and 200/400V output was fabricated and tested. Efficiency goal of 97% was proven achievable through hardware experiment. This DC to DC converter was then modified in the later stage to converter 35 to 63 V input and 13.8 V output for automotive charging applications. The complete prototype was tested at Delphi with their solid oxide fuel cell test stand to verify the performance of the modified DC to DC converter. The output was tested up to 3-kW level, and the efficiency exceeded 97.5%. Multiple-phase interleaving operation design was proved to be reliable and ripple free at the output, which is desirable for the battery charging. Overall this is a very successful collaboration project between the SECA Core Technology Team and Industrial Team.

  2. IGBT convertor with active snubber for soft switching. [Insulated Gate Bipolar Transistor

    NASA Technical Reports Server (NTRS)

    Masserant, B. J.; Shriver, J.; Stuart, T. A.

    1991-01-01

    This full bridge dc-dc convertor with IGBTs uses zero voltage switching (ZVS) for one leg of the bridge and zero current switching (ZCS) for the other. It is shown that an active snubber greatly improves the performance over previous methods. Experimental results are shown for a 6 kW circuit switching at 20 kHz.

  3. Investigation of Timing to Switch Control Mode in Powered Knee Prostheses during Task Transitions

    PubMed Central

    Zhang, Fan; Liu, Ming; Huang, He

    2015-01-01

    Current powered prosthetic legs require switching control modes according to the task the user is performing (e.g. level-ground walking, stair climbing, walking on slopes, etc.). To allow prosthesis users safely and seamlessly transition between tasks, it is critical to determine when to switch the prosthesis control mode during task transitions. Our previous study defined critical timings for different types of task transitions in ambulation; however, it is unknown whether it is the unique timing that allows safe and seamless transitions. The goals of this study were to (1) systematically investigate the effects of mode switch timing on the prosthesis user’s performance in task transitions, and (2) identify appropriate timing to switch the prosthesis control mode so that the users can seamlessly transition between different locomotion tasks. Five able-bodied (AB) and two transfemoral (TF) amputee subjects were tested as they wore a powered knee prosthesis. The prosthesis control mode was switched manually at various times while the subjects performed different types of task transitions. The subjects’ task transition performances were evaluated by their walking balance and success in performing seamless task transitions. The results demonstrated that there existed a time window within which switching the prosthesis control mode neither interrupted the subjects’ task transitions nor disturbed their walking balance. Therefore, the results suggested the control mode switching of a lower limb prosthesis can be triggered within an appropriate time window instead of a specific timing or an individual phase. In addition, a generalized criterion to determine the appropriate mode switch timing was proposed. The outcomes of this study could provide important guidance for future designs of neurally controlled powered knee prostheses that are safe and reliable to use. PMID:26197084

  4. Investigation of Timing to Switch Control Mode in Powered Knee Prostheses during Task Transitions.

    PubMed

    Zhang, Fan; Liu, Ming; Huang, He

    2015-01-01

    Current powered prosthetic legs require switching control modes according to the task the user is performing (e.g. level-ground walking, stair climbing, walking on slopes, etc.). To allow prosthesis users safely and seamlessly transition between tasks, it is critical to determine when to switch the prosthesis control mode during task transitions. Our previous study defined critical timings for different types of task transitions in ambulation; however, it is unknown whether it is the unique timing that allows safe and seamless transitions. The goals of this study were to (1) systematically investigate the effects of mode switch timing on the prosthesis user's performance in task transitions, and (2) identify appropriate timing to switch the prosthesis control mode so that the users can seamlessly transition between different locomotion tasks. Five able-bodied (AB) and two transfemoral (TF) amputee subjects were tested as they wore a powered knee prosthesis. The prosthesis control mode was switched manually at various times while the subjects performed different types of task transitions. The subjects' task transition performances were evaluated by their walking balance and success in performing seamless task transitions. The results demonstrated that there existed a time window within which switching the prosthesis control mode neither interrupted the subjects' task transitions nor disturbed their walking balance. Therefore, the results suggested the control mode switching of a lower limb prosthesis can be triggered within an appropriate time window instead of a specific timing or an individual phase. In addition, a generalized criterion to determine the appropriate mode switch timing was proposed. The outcomes of this study could provide important guidance for future designs of neurally controlled powered knee prostheses that are safe and reliable to use.

  5. Generalized computer-aided discrete time domain modeling and analysis of dc-dc converters

    NASA Technical Reports Server (NTRS)

    Lee, F. C.; Iwens, R. P.; Yu, Y.; Triner, J. E.

    1977-01-01

    A generalized discrete time domain modeling and analysis technique is presented for all types of switching regulators using any type of duty-cycle controller, and operating in both continuous and discontinuous inductor current. State space techniques are employed to derive an equivalent nonlinear discrete time model that describes the converter exactly. The system is linearized about its equilibrium state to obtain a linear discrete time model for small signal performance evaluations, such as stability, audiosusceptibility and transient response. The analysis makes extensive use of the digital computer as an analytical tool. It is universal, exact and easy to use.

  6. On Optimal Control of Non-Autonomous Switched Systems with a Fixed Mode Sequence

    NASA Technical Reports Server (NTRS)

    Kamgarpour, Maryam; Tomlin, Claire

    2012-01-01

    We consider differentiability with respect to the switch times of the value function of an optimal control problem for a non-autonomous switched system. The control variables are the switch times between the modes and the input in each mode. We provide a method to compute the derivative of the cost function given a nominal input. Then, we view the optimal control problem as a parametrized optimization problem in which the switch times are the parameters and the optimization is over the set of feasible inputs of each mode. From this point of view, we provide conditions under which the continuity and differentiability of the optimal value function, that is the cost function optimized over the inputs, can be guaranteed.

  7. Enhancement Mode Power Switching AlGaN HEMTs

    DTIC Science & Technology

    2013-05-14

    analyzer ( MTA ). The diplexer and second harmonic termination branch were removed. The output power meter was replaced by the MTA . On the input side...have been removed, and the output power meters have been replaced by an MTA . To test switching performance, devices are often measured with the aid of

  8. Local digital control of power electronic converters in a dc microgrid based on a-priori derivation of switching surfaces

    NASA Astrophysics Data System (ADS)

    Banerjee, Bibaswan

    In power electronic basedmicrogrids, the computational requirements needed to implement an optimized online control strategy can be prohibitive. The work presented in this dissertation proposes a generalized method of derivation of geometric manifolds in a dc microgrid that is based on the a-priori computation of the optimal reactions and trajectories for classes of events in a dc microgrid. The proposed states are the stored energies in all the energy storage elements of the dc microgrid and power flowing into them. It is anticipated that calculating a large enough set of dissimilar transient scenarios will also span many scenarios not specifically used to develop the surface. These geometric manifolds will then be used as reference surfaces in any type of controller, such as a sliding mode hysteretic controller. The presence of switched power converters in microgrids involve different control actions for different system events. The control of the switch states of the converters is essential for steady state and transient operations. A digital memory look-up based controller that uses a hysteretic sliding mode control strategy is an effective technique to generate the proper switch states for the converters. An example dcmicrogrid with three dc-dc boost converters and resistive loads is considered for this work. The geometric manifolds are successfully generated for transient events, such as step changes in the loads and the sources. The surfaces corresponding to a specific case of step change in the loads are then used as reference surfaces in an EEPROM for experimentally validating the control strategy. The required switch states corresponding to this specific transient scenario are programmed in the EEPROM as a memory table. This controls the switching of the dc-dc boost converters and drives the system states to the reference manifold. In this work, it is shown that this strategy effectively controls the system for a transient condition such as step changes

  9. Doubly active Q switching and mode locking of an all-fiber laser.

    PubMed

    Cuadrado-Laborde, Christian; Díez, Antonio; Cruz, Jose L; Andrés, Miguel V

    2009-09-15

    Simultaneous and independent active Q switching and active mode locking of an erbium-doped fiber laser is demonstrated using all-fiber modulation techniques. A magnetostrictive rod attached to the output fiber Bragg grating modulates the Q factor of the Fabry-Perot cavity, whereas active mode locking is achieved by amplitude modulation with a Bragg-grating-based acousto-optic device. Fully modulated Q-switched mode-locked trains of optical pulses were obtained for a wide range of pump powers and repetition rates. For a Q-switched repetition rate of 500 Hz and a pump power of 100 mW, the laser generates trains of 12-14 mode-locked pulses of about 1 ns each, within an envelope of 550 ns, an overall energy of 0.65 microJ, and a peak power higher than 250 W for the central pulses of the train.

  10. Microprocessor control of multiple peak power tracking DC/DC converters for use with solar cell arrays

    NASA Technical Reports Server (NTRS)

    Frederick, Martin E. (Inventor); Jermakian, Joel (Inventor)

    1991-01-01

    A method and an apparatus is provided for efficiently controlling the power output of a solar cell array string or a plurality of solar cell array strings to achieve a maximum amount of output power from the strings under varying conditions of use. Maximum power output from a solar array string is achieved through control of a pulse width modulated DC/DC buck converter which transfers power from a solar array to a load or battery bus. The input voltage from the solar array to the converter is controlled by a pulse width modulation duty cycle, which in turn is controlled by a differential signal controller. By periodically adjusting the control voltage up or down by a small amount and comparing the power on the load or bus with that generated at different voltage values a maximum power output voltage may be obtained. The system is totally modular and additional solar array strings may be added to the system simply by adding converter boards to the system and changing some constants in the controller's control routines.

  11. Mathematical modeling analysis of regenerative solid oxide fuel cells in switching mode conditions

    NASA Astrophysics Data System (ADS)

    Jin, Xinfang; Xue, Xingjian

    A 2D transient mathematical model is developed for regenerative solid oxide cells operated in both SOFC mode and SOEC mode. The steady state performance of the model is validated using experimental results of in-house prepared NiO-YSZ/YSZ/LSM cell under different operating temperatures. The model is employed to investigate complicated multi-physics processes during the transient process of mode switching. Simulation results indicate that the trend of internal parameter distributions, including H 2/O 2/H 2O and ionic potentials, flip when the operating cell is switched from one mode to another. However, the electronic potential shows different behaviors. At H 2 electrode, electronic potential keeps at zero voltage level, while at O 2 electrode, it increases from a relatively low level in SOFC mode to a relatively high level in SOEC mode. Transient results also show that an overshooting phenomenon occurs for mass fraction distribution of water vapor at H 2 side when the operating cell switches from SOFC mode to SOEC mode. The mass fractions of O 2 and H 2 as well as charge (electrons and ions) potentials may quickly follow the operating mode changes without over-shootings. The simulation results facilitate the internal mechanism understanding for regenerative SOFCs.

  12. Location of the emitting regions in the mode-switching radio pulsar PSR 1926 + 18

    NASA Technical Reports Server (NTRS)

    Nowakowski, L. A.

    1994-01-01

    We present an analysis of average single-frequency profiles of the radio pulsar PSR 1926 + 18 in two different modes. Assuming a purely dipolar field and taking into account retardation, aberration, magnetic line curvature, and ignoring the magnetic field line sweepback, we come to the following conclusions: (1) mode switching in PSR 1926 + 18 at 430 MHz may be understood in terms of different emission heights of the two modes; (2) the weaker mode appears when regions emitting the first two components move away from the star by an additional distance of not more than several kilometers from their original locations; (3) the trailing conal component is emitted essentially from the same layer of the magnetosphere in both modes, in contrast to the first conal component, which appears to change its location in the magnetosphere; (4) core and conal components are emitted from distinctly different emission heights: core components not more than 75 km, and conal components not less than 215 km from the surface of the star. Our model infers three-dimensional information about the emitting region from single-frequency observations. It has been tested previously with a mode switching pulsar that had one component in the average profile in two modes. This paper shows that the same model can explain positions and widths of the components in a more complex profile during mode switching, provided that the components can be traced from one mode to another.

  13. Noisy Inflows Cause a Shedding-Mode Switching in Flow Past an Oscillating Cylinder

    NASA Astrophysics Data System (ADS)

    Lucor, Didier; Karniadakis, George Em

    2004-04-01

    Vortex streets formed behind oscillating bluff bodies consist of arrays of groups of two, three, or four vortices classified as 2S, P+S, and 2P shedding modes, respectively. The prevailing dominant mode depends primarily on the amplitude and the frequency of the oscillation and on the Reynolds number. We investigate the effect of noise at the inflow on the stability of these vortex modes in laminar flow past a circular cylinder. We employ stochastic simulations based on a new polynomial chaos method to study the shedding-mode switching from a P+S pattern to a 2S mode in the presence of noise.

  14. MEMS switching of contour-mode aluminum nitride resonators for switchable and reconfigurable radio frequency filters

    NASA Astrophysics Data System (ADS)

    Nordquist, Christopher D.; Branch, Darren W.; Pluym, Tammy; Choi, Sukwon; Nguyen, Janet H.; Grine, Alejandro; Dyck, Christopher W.; Scott, Sean M.; Sing, Molly N.; Olsson, Roy H., III

    2016-10-01

    Switching of transducer coupling in aluminum nitride contour-mode resonators provides an enabling technology for future tunable and reconfigurable filters for multi-function RF systems. By using microelectromechanical capacitive switches to realize the transducer electrode fingers, coupling between the metal electrode finger and the piezoelectric material is modulated to change the response of the device. On/off switched width extensional resonators with an area of  <0.2 mm2 demonstrate a Q of 2000, K 2 of 0.72, and  >24 dB switching ratio at a resonator center frequency of 635 MHz. Other device examples include a 63 MHz resonator with switchable impedance and a 470 MHz resonator with 127 kHz of fine center frequency tuning accomplished by mass loading of the resonator with the MEMS switches.

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

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  16. Transient Performance Improvement Circuit (TPIC)s for DC-DC converter applications

    NASA Astrophysics Data System (ADS)

    Lim, Sungkeun

    of the slow inductor current slew rate which is determined by the input voltage, output voltage, and the inductance. The remaining inductor current in the power delivery path will charge the output capacitors and develop a voltage across the ESR. As a result, large output voltage spikes occur during load current transients. Due to their limited control bandwidth, traditional VRs can not sufficiently respond rapidly to certain load transients. As a result, a large output voltage spike can occur during load transients, hence requiring a large amount of bulk capacitance to decouple the VR from the load [2]. If the remaining inductor current is removed from the power stage or the inductor current slew rate is changed, the output voltage spikes can be clamped, allowing the output capacitance to be reduced. A new design methodology for a Transient Performance Improvement Circuit(TPIC) based on controlling the output impedance of a regulator is presented. The TPIC works in parallel with a voltage regulator (VR)'s ceramic capacitors to achieve faster voltage regulation without the need for a large bulk capacitance, and can serve as a replacement for bulk capacitors. The specific function of the TPIC is to mimic the behavior of the bulk capacitance in a traditional VRM by sinking and sourcing large currents during transients, allowing the VR to respond quickly to current transients without the need for a large bulk capacitance. This will allow fast transient response without the need for a large bulk capacitor. The main challenge in applying the TPIC is creating a design which will not interfere with VR operation. A TPIC for a 4 Switch Buck-Boost (4SBB) converter is presented which functions by con- trolling the inductor current slew rate during load current transients. By increasing the inductor current slew rate, the remaining inductor current can be removed from the 4SBB power delivery path and the output voltage spike can be clamped. A second TPIC is presented which is

  17. 1 kW, 9 kV dc-dc converter module with time-sharing control of output voltage and input current

    SciTech Connect

    Borgatti, R.; Stefani, R.; Bressan, O.; Bicciato, F.; Tenti, P.; Rossetto, L.

    1993-10-01

    The paper describes a dc-dc power module based on a single-stage current-fed converter structure. Control is made according to a time-sharing strategy allowing simultaneous regulation of output voltage and input current. This solution is suitable for high-performance space and avionic applications, giving high efficiency, compactness, and accuracy, speed and robustness of control. Theoretical analysis, design criteria, and experimental results are reported. Application to radar supplies is discussed.

  18. Soft switch-avalanche IGBT convertor. [Insulated Gate Bipolar Transistor

    NASA Technical Reports Server (NTRS)

    Chen, K.; Stuart, T. A.

    1990-01-01

    A full bridge dc-dc converter using a zero voltage and zero current switching technique is described. This circuit utilizes the characteristics of the IGBT to achieve power and frequency combinations that are much higher than those previously reported for this device. Experimental results are included for a 1.5 kW, 100 kHz converter with 94 percent efficiency.

  19. Soft switch-avalanche IGBT convertor. [Insulated Gate Bipolar Transistor

    NASA Technical Reports Server (NTRS)

    Chen, K.; Stuart, T. A.

    1990-01-01

    A full bridge dc-dc converter using a zero voltage and zero current switching technique is described. This circuit utilizes the characteristics of the IGBT to achieve power and frequency combinations that are much higher than those previously reported for this device. Experimental results are included for a 1.5 kW, 100 kHz converter with 94 percent efficiency.

  20. Simultaneously Q-switched and mode-locked passive modulators for the microchip lasers

    NASA Astrophysics Data System (ADS)

    Chen, Junewen; Lin, Jun-Ting; Hung, Te-Chien

    2004-07-01

    Five kinds of the laser passive modulators: single crystal semiconductor wafers, plastic dye sheets, lithium fluoride crystals containing F2- color center, chromium yttrium aluminum garnet crystals and ionic color filter glass that can Q-switched modulate, mode-locked modulate, and Q-switched mode-locking modulate the conventional flash-lamp pumped Nd:hosted lasers, Er:Glass eye-safe solid-state lasers as well as all those of diode-pumped Nd:hosted and Er:Glass eye-safe microchip lasers are presented. Theoretical model are proposed and the detail analysis are presented.

  1. A general unified approach to modelling switching dc-to-dc converters in discontinuous conduction mode

    NASA Technical Reports Server (NTRS)

    Cuk, S.; Middlebrook, R. D.

    1977-01-01

    A method for modelling switching converters in the discontinuous conduction mode is developed, whose starting point is the unified state-space representation, and whose end result is a complete linear circuit model which correctly represents all essential features, namely, the input, output, and transfer properties (static dc as well as dynamic ac small signal). While the method is generally applicable to any switching converter operating in the discontinuous conduction mode, it is extensively illustrated for the three common power stages (buck, boost, and buck-boost). The results for these converters are then easily tabulated owing to the fixed equivalent circuit topology of their canonical circuit model.

  2. A novel adaptive switching function on fault tolerable sliding mode control for uncertain stochastic systems.

    PubMed

    Zahiripour, Seyed Ali; Jalali, Ali Akbar

    2014-09-01

    A novel switching function based on an optimization strategy for the sliding mode control (SMC) method has been provided for uncertain stochastic systems subject to actuator degradation such that the closed-loop system is globally asymptotically stable with probability one. In the previous researches the focus on sliding surface has been on proportional or proportional-integral function of states. In this research, from a degree of freedom that depends on designer choice is used to meet certain objectives. In the design of the switching function, there is a parameter which the designer can regulate for specified objectives. A sliding-mode controller is synthesized to ensure the reachability of the specified switching surface, despite actuator degradation and uncertainties. Finally, the simulation results demonstrate the effectiveness of the proposed method.

  3. All-optical switch using optically controlled two mode interference coupler.

    PubMed

    Sahu, Partha Pratim

    2012-05-10

    In this paper, we have introduced optically controlled two-mode interference (OTMI) coupler having silicon core and GaAsInP cladding as an all-optical switch. By taking advantage of refractive index modulation by launching optical pulse into cladding region of TMI waveguide, we have shown optically controlled switching operation. We have studied optical pulse-controlled coupling characteristics of the proposed device by using a simple mathematical model on the basis of sinusoidal modes. The device length is less than that of previous work. It is also seen that the cross talk of the OTMI switch is not significantly increased with fabrication tolerances (±δw) in comparison with previous work.

  4. Aegean wall lizards switch foraging modes, diet, and morphology in a human-built environment.

    PubMed

    Donihue, Colin M

    2016-10-01

    Foraging mode is a functional trait with cascading impacts on ecological communities. The foraging syndrome hypothesis posits a suite of concurrent traits that vary with foraging mode; however, comparative studies testing this hypothesis are typically interspecific. While foraging modes are often considered typological for a species when predicting foraging-related traits or mode-specific cascading impacts, intraspecific mode switching has been documented in some lizards. Mode-switching lizards provide an opportunity to test foraging syndromes and explore how intraspecific variability in foraging mode might affect local ecological communities.Because lizard natural history is intimately tied to habitat use and structure, I tested for mode switching between populations of the Aegean wall lizard, Podarcis erhardii, inhabiting undisturbed habitat and human-built rock walls on the Greek island of Naxos. I observed foraging behavior among 10 populations and tested lizard morphological and performance predictions at each site. Furthermore, I investigated the diet of lizards at each site relative to the available invertebrate community.I found that lizards living on rock walls were significantly more sedentary-sit and wait-than lizards at nonwall sites. I also found that head width increased in females and the ratio of hindlimbs to forelimbs in both sexes increased as predicted. Diet also changed, with nonwall lizards consuming a higher proportion of sedentary prey. Lizard bite force also varied significantly between sites; however, the pattern observed was opposite to that predicted, suggesting that bite force in these lizards may more closely relate to intraspecific competition than to diet.This study demonstrates microgeographic variability in lizard foraging mode as a result of human land use. In addition, these results demonstrate that foraging mode syndromes can shift intraspecifically with potential cascading effects on local ecological communities.

  5. Generalized Simulation Model for a Switched-Mode Power Supply Design Course Using MATLAB/SIMULINK

    ERIC Educational Resources Information Center

    Liao, Wei-Hsin; Wang, Shun-Chung; Liu, Yi-Hua

    2012-01-01

    Switched-mode power supplies (SMPS) are becoming an essential part of many electronic systems as the industry drives toward miniaturization and energy efficiency. However, practical SMPS design courses are seldom offered. In this paper, a generalized MATLAB/SIMULINK modeling technique is first presented. A proposed practical SMPS design course at…

  6. Generalized Simulation Model for a Switched-Mode Power Supply Design Course Using MATLAB/SIMULINK

    ERIC Educational Resources Information Center

    Liao, Wei-Hsin; Wang, Shun-Chung; Liu, Yi-Hua

    2012-01-01

    Switched-mode power supplies (SMPS) are becoming an essential part of many electronic systems as the industry drives toward miniaturization and energy efficiency. However, practical SMPS design courses are seldom offered. In this paper, a generalized MATLAB/SIMULINK modeling technique is first presented. A proposed practical SMPS design course at…

  7. Nonpolar resistive memory switching with all four possible resistive switching modes in amorphous LaHoO3 thin films

    NASA Astrophysics Data System (ADS)

    Sharma, Yogesh; Pavunny, Shojan P.; Fachini, Esteban; Scott, James F.; Katiyar, Ram S.

    2015-09-01

    We studied the resistive memory switching in pulsed laser deposited amorphous LaHoO3 (a-LHO) thin films for non-volatile resistive random access memory applications. Nonpolar resistive switching (RS) was achieved in Pt/a-LHO/Pt memory cells with all four possible RS modes (i.e., positive unipolar, positive bipolar, negative unipolar, and negative bipolar) having high RON/ROFF ratios (in the range of ˜104-105) and non-overlapping switching voltages (set voltage, VON ˜ ±3.6-4.2 V and reset voltage, VOFF ˜ ±1.3-1.6 V) with a small variation of about ±5-8%. Temperature dependent current-voltage (I-V) characteristics indicated the metallic conduction in low resistance states (LRS). We believe that the formation (set) and rupture (reset) of mixed conducting filaments formed out of oxygen vacancies and metallic Ho atoms could be responsible for the change in the resistance states of the memory cell. Detailed analysis of I-V characteristics further corroborated the formation of conductive nanofilaments based on metal-like (Ohmic) conduction in LRS. Simmons-Schottky emission was found to be the dominant charge transport mechanism in the high resistance state.

  8. Reexamining the beat Cepheid TU CAS - No second overtone, no mode switching

    NASA Astrophysics Data System (ADS)

    Matthews, Jaymie M.; Gieren, Wolfgang P.; Fernie, J. D.; Dinshaw, Nadine

    1992-08-01

    Simultaneous photometry and radial-velocity measurements of the double-mode Cepheid TU Cas were obtained in 1987, to check on the mode behavior of this star after a decade-long gap in the observing record. Least-squares fits of these data are performed to isolate the primary (2.14 d) and secondary (1.52 d) variations. The residuals of the present solution rule out the existence of any tertiary mode with V and velocity amplitudes greater than 0.004 mag and 0.7 km/s, respectively, contradicting Faulkner's (1977) report of such a mode with amplitude 0.05 mag. Nor is a significant change detected in the relative amplitudes of the modes compared to previous data, cited as evidence for mode switching in this star by earlier investigators.

  9. Switching the mode of sucrose utilization by Saccharomyces cerevisiae

    PubMed Central

    Badotti, Fernanda; Dário, Marcelo G; Alves, Sergio L; Cordioli, Maria Luiza A; Miletti, Luiz C; de Araujo, Pedro S; Stambuk, Boris U

    2008-01-01

    Background Overflow metabolism is an undesirable characteristic of aerobic cultures of Saccharomyces cerevisiae during biomass-directed processes. It results from elevated sugar consumption rates that cause a high substrate conversion to ethanol and other bi-products, severely affecting cell physiology, bioprocess performance, and biomass yields. Fed-batch culture, where sucrose consumption rates are controlled by the external addition of sugar aiming at its low concentrations in the fermentor, is the classical bioprocessing alternative to prevent sugar fermentation by yeasts. However, fed-batch fermentations present drawbacks that could be overcome by simpler batch cultures at relatively high (e.g. 20 g/L) initial sugar concentrations. In this study, a S. cerevisiae strain lacking invertase activity was engineered to transport sucrose into the cells through a low-affinity and low-capacity sucrose-H+ symport activity, and the growth kinetics and biomass yields on sucrose analyzed using simple batch cultures. Results We have deleted from the genome of a S. cerevisiae strain lacking invertase the high-affinity sucrose-H+ symporter encoded by the AGT1 gene. This strain could still grow efficiently on sucrose due to a low-affinity and low-capacity sucrose-H+ symport activity mediated by the MALx1 maltose permeases, and its further intracellular hydrolysis by cytoplasmic maltases. Although sucrose consumption by this engineered yeast strain was slower than with the parental yeast strain, the cells grew efficiently on sucrose due to an increased respiration of the carbon source. Consequently, this engineered yeast strain produced less ethanol and 1.5 to 2 times more biomass when cultivated in simple batch mode using 20 g/L sucrose as the carbon source. Conclusion Higher cell densities during batch cultures on 20 g/L sucrose were achieved by using a S. cerevisiae strain engineered in the sucrose uptake system. Such result was accomplished by effectively reducing sucrose

  10. Efficient graphene Q switching and mode locking of 1.34 μm neodymium lasers.

    PubMed

    Xu, Jin-Long; Li, Xian-Lei; He, Jing-Liang; Hao, Xiao-Peng; Yang, Ying; Wu, Yong-Zhong; Liu, Shan-De; Zhang, Bai-Tao

    2012-07-01

    We demonstrate that few-layered graphene sheets used as a saturable absorber can provide efficient Q-switching and mode-locking modulation in 1.34 μm Nd:GdVO(4) bulk lasers. The minimum Q-switched pulses were 450 ns for 260 mW average power, 43 kHz repetition rate, and 2.5 μJ pulse energy. For the mode-locked laser, an average power of 1.29 W was achieved with 11 ps pulse duration and 13 nJ pulse energy. To our knowledge, this average power is the highest yet obtained from a graphene mode-locked laser, and the corresponding optical-optical efficiency of 23% is the best result among 1.3 μm neodymium mode-locked lasers. The quality factor M(2) of the Q-switched beam was 1.4 and 1.6 in the horizontal and longitudinal planes, respectively, and the M(2) of the mode-locked beam reached 1.1 and 1.0. These results clearly indicate the advantages of few-layered graphene as a saturable absorber.

  11. Design of sliding mode control for a class of uncertain switched systems

    NASA Astrophysics Data System (ADS)

    Liu, Yonghui; Jia, Tinggang; Niu, Yugang; Zou, Yuanyuan

    2015-04-01

    This paper considers the problem of sliding mode control for a class of uncertain switched systems with parameter uncertainties and external disturbances. A key feature of the controlled system is that each subsystem is not required to share the same input channel, which was usually assumed in some existing works. By means of a weighted sum of the input matrix, a common sliding surface is designed in this work. It is shown that the reachability of the sliding surface can be ensured by the present sliding mode controller. Moreover, the sliding motion on the specified sliding surface is asymptotically stable under the proposed switching signal dependent on the state and time. Additionally, the above results are further extended to the case that the system states are unavailable. Both the sliding surface and sliding mode controller are designed by utilising state-observer. Finally, numerical simulation examples are given to illustrate the effectiveness of the present method.

  12. Novel Trajectory Control for Human Cooperation Robot Based on Behavior Mode Switching

    NASA Astrophysics Data System (ADS)

    Seki, Hirokazu; Takahashi, Kazuki; Tadakuma, Susumu

    This paper describes a novel trajectory control system for human cooperation robots based on behavior mode switching. Human cooperation robots have the great possibility to serve as useful support systems for elderly people and physically handicapped people and it is expected to realize the smooth and human-friendly support movements. This study defines three behavior modes in human cooperation motion and their respective trajectory control system are designed. In the trajectory design, minimum jerk model is introduced to realize the smooth and human-friendly cooperation movements. In addition, the initial value compensation at the mode switching is also developed. Some experiments on two-axis plane robot and performance evaluation by trial subjects show the effectiveness of the proposed trajectory control system.

  13. Fast electrical switching of orbital angular momentum modes using ultra-compact integrated vortex emitters.

    PubMed

    Strain, Michael J; Cai, Xinlun; Wang, Jianwei; Zhu, Jiangbo; Phillips, David B; Chen, Lifeng; Lopez-Garcia, Martin; O'Brien, Jeremy L; Thompson, Mark G; Sorel, Marc; Yu, Siyuan

    2014-09-17

    The ability to rapidly switch between orbital angular momentum modes of light has important implications for future classical and quantum systems. In general, orbital angular momentum beams are generated using free-space bulk optical components where the fastest reconfiguration of such systems is around a millisecond using spatial light modulators. In this work, an extremely compact optical vortex emitter is demonstrated with the ability to actively tune between different orbital angular momentum modes. The emitter is tuned using a single electrically contacted thermo-optical control, maintaining device simplicity and micron scale footprint. On-off keying and orbital angular momentum mode switching are achieved at rates of 10 μs and 20 μs respectively.

  14. Exercise mode and executive function in older adults: an ERP study of task-switching.

    PubMed

    Dai, Chih-Ta; Chang, Yu-Kai; Huang, Chung-Ju; Hung, Tsung-Min

    2013-11-01

    The purpose of this study was to investigate the relationship between exercise mode and executive function and its effect on behavior and neuroelectric activity. Forty-eight older adults were classified into open-skill, closed-skill, and irregular exercise groups based on their experience of exercise participation. Executive function was measured via a task-switching paradigm, in which the behavioral indices and event-related potentials elicited by task-switching were assessed. The results revealed that the exercise groups, regardless of the exercise mode, exhibited faster reaction times in both global and local switches than the irregular exercise group, regardless of the within-task conditions. Similarly, larger P3 amplitudes were observed in both exercise groups compared to the irregular exercise group. Moreover, additional facilitation effects of open-skill exercises on global switch costs were observed, whereas no differences in local switch costs were found among the three groups. The results replicate previous studies that have reported generally improved executive function after participation in exercises; additionally, they extend the current knowledge by indicating that these cognitive improvements in specific aspects of executive function could also be obtained from open-skill exercises. Copyright © 2013 Elsevier Inc. All rights reserved.

  15. Switching bipolar hepatic radiofrequency ablation using internally cooled wet electrodes: comparison with consecutive monopolar and switching monopolar modes

    PubMed Central

    Yoon, J H; Woo, S; Hwang, E J; Hwang, I; Choi, W; Han, J K; Choi, B I

    2015-01-01

    Objective: To evaluate whether switching bipolar radiofrequency ablation (SB-RFA) using three internally cooled wet (ICW) electrodes can induce coagulations >5 cm in porcine livers with better efficiency than consecutive monopolar (CM) or switching monopolar (SM) modes. Methods: A total of 60 coagulations were made in 15 in vivo porcine livers using three 17-gauge ICW electrodes and a multichannel radiofrequency (RF) generator. RF energy (approximately 200 W) was applied in CM mode (Group A, n = 20) for 24 min, SM mode for 12 min (Group B, n = 20) or switching bipolar (SB) mode for 12 min (Group C, n = 20) in in vivo porcine livers. Thereafter, the delivered RFA energy, as well as the shape and dimension of coagulations were compared among the groups. Results: Spherical- or oval-shaped ablations were created in 30% (6/20), 85% (17/20) and 90% (18/20) of coagulations in the CM, SM and SB groups, respectively (p = 0.003). SB-RFA created ablations >5 cm in minimum diameter (Dmin) in 65% (13/20) of porcine livers, whereas SM- or CM-RFA created ablations >5 cm in only 25% (5/20) and 20% (4/20) of porcine livers, respectively (p = 0.03). The mean Dmin of coagulations was significantly larger in Group C than in Groups A and B (5.1 ± 0.9, 3.9 ± 1.2 and 4.4 ± 1.0 cm, respectively, p = 0.002) at a lower delivered RF energy level (76.8 ± 14.3, 120.9 ± 24.5 and 114.2 ± 18.3 kJ, respectively, p < 0.001). Conclusion: SB-RFA using three ICW electrodes can create coagulations >5 cm in diameter with better efficiency than do SM- or CM-RFA. Advances in knowledge: SB-RFA can create large, regular ablation zones with better time–energy efficiency than do CM- or SM-RFA. PMID:25873479

  16. A harmonic cancellation technique for an ultrasound transducer excited by a switched-mode power converter.

    PubMed

    Tang, Sai Chun; Clement, Gregory T

    2008-02-01

    The aim of this study is to evaluate the feasibility of using harmonic cancellation for a therapeutic ultrasound transducer excited by a switched-mode power converter without an additional output filter. A switching waveform without the third harmonic was created by cascading two switched-mode power inverter modules at which their output waveforms were pi/3 phase shifted from each other. A PSPICE simulation model for the power converter output stage was developed. The simulated results were in good agreement with the measurement. The waveform and harmonic contents of the acoustic pressure generated by a 1-MHz, self-focused piezoelectric transducer with and without harmonic cancellation have been evaluated. Measured results indicated that the acoustic third harmonicto- fundamental ratio at the focus was small (-48 dB) with harmonic cancellation, compared to that without harmonic cancellation (-20 dB). The measured acoustic levels of the fifth harmonic for both cases with and without harmonic cancellation also were small (-46 dB) compared to the fundamental. This study shows that it is viable to drive a piezoelectric ultrasound transducer using a switched-mode power converter without the requirement of an additional output filter in many high-intensity focused ultrasound (HIFU) applications.

  17. Ultrahigh refractive index sensitivity and tunable polarization switching via infrared plasmonic lattice modes

    NASA Astrophysics Data System (ADS)

    Gutha, Rithvik R.; Sadeghi, Seyed M.; Wing, Waylin J.

    2017-04-01

    We demonstrate tunable polarization-dependent infrared plasmonic lattice modes in the range of 1 to 1.7 μm in arrays of large gold nanodisks with a rectangle lattice structure. We show that when these arrays are exposed to air, their main mode appears around 1 μm. Under this condition, addition of chemicals leads to significant wavelength shifts in this mode, offering a refractive index sensitivity of about 795 nm/RIU (refractive index unit). Our results show that this process is accompanied by excitation of a sharp peak associated with an infrared lattice mode at about 1.62 μm, suggesting an abrupt refractive-index switching of the collective modes of the arrays. By depositing ultrathin layers of Si, we show that the wavelength of the 1 μm mode can be shifted, covering the whole telecom band ranges. We demonstrate that this can lead to tunable narrow- and wide-band polarization switching of the collective modes of the arrays within this range with a high extinction ratio.

  18. Design of a high voltage input - output ratio dc-dc converter dedicated to small power fuel cell systems

    NASA Astrophysics Data System (ADS)

    Béthoux, O.; Cathelin, J.

    2010-12-01

    Consuming chemical energy, fuel cells produce simultaneously heat, water and useful electrical power [J.M. Andújar, F. Segura, Renew. Sust. Energy Rev. 13, 2309 (2009)], [J. Larminie, A. Dicks, Fuel Cell Systems Explained, 2nd edn. (John Wiley & Sons, 2003)]. As a matter of fact, the voltage generated by a fuel cell strongly depends on both the load power demand and the operating conditions. Besides, as a result of many design aspects, fuel cells are low voltage and high current electric generators. On the contrary, electric loads are commonly designed for small voltage swing and a high V/I ratio in order to minimize Joule losses. Therefore, electric loads supplied by fuel cells are typically fed by means of an intermediate power voltage regulator. The specifications of such a power converter are to be able to step up the input voltage with a high ratio (a ratio of 10 is a classic situation) and also to work with an excellent efficiency (in order to minimize its size, its weight and its losses) [A. Shahin, B. Huang, J.P. Martin, S. Pierfederici, B. Davat, Energy Conv. Manag. 51, 56 (2010)]. This paper deals with the design of this essential ancillary device. It intends to bring out the best structure for fulfilling this function. Several dc-dc converters with large voltage step-up ratios are introduced. A topology based on a coupled inductor or tapped inductor is closely studied. A detailed modelling is performed with the purpose of providing designing rules. This model is validated with both simulation and implementation. The experimental prototype is based on the following specifications: the fuel cell output voltage ranges from a 50 V open-voltage to a 25 V rated voltage while the load requires a constant 250 V voltage. The studied coupled inductor converter is compared with a classic boost converter commonly used in this voltage elevating application. Even though the voltage regulator faces severe FC specifications, the measured efficiency reaches 96% at the

  19. Investigation of thyristor-based switches triggered in impact-ionization wave mode

    NASA Astrophysics Data System (ADS)

    Gusev, A. I.; Lyubutin, S. K.; Rukin, S. N.; Slovikovsky, B. G.; Tsyranov, S. N.

    2017-05-01

    An operation of the thyristor-based switches triggered in impact-ionization wave mode has been investigated. The thyristor switch contained two series connected tablet thyristors having a silicon wafer of 56 mm diameter. Applying across the switch a triggering pulse with a voltage rise rate dU/dt of over 1 kV/ns, the thyristors transition time to a conductive state was reduced to shorter than 1 ns. It is shown that the maximum amplitude of a no-failure current is increased with increasing dU/dt at the triggering stage. A possible mechanism of the dU/dt value effect on the thyristors breakdown current is discussed. Under a safety operation regime at dU/dt = 6 kV/ns (3 kV/ns per a single thyristor), the switch discharged 1-mF capacitor, which was charged to a voltage of 5 kV, to a resistive load of 18 mΩ. The following results were obtained: a peak current was 200 kA, an initial dI/dt was 58 kA/µs, a FWHM was 25 µs, and a switching efficiency was 0.97. It is shown also that a temperature of the silicon wafer is one of the main factors that affects on the thyristor switching process.

  20. Exercise-mode-related changes in task-switching performance in the elderly.

    PubMed

    Tsai, Chia-Liang; Wang, Wen-Liang

    2015-01-01

    The objective of the current study was to explore the relationships between exercise modes and executive functions in the elderly. Twenty-one elderly individuals in the open-skill group, 22 in the closed-skill group, and 21 in the sedentary-behavior (control) group were recruited in the current study, and performed a task-switching paradigm during which the switches occurred unpredictably and infrequently, while the behavioral and electrophysiological performances were assessed simultaneously. The results indicated that although there were no group differences in accuracy rates, the two exercise groups exhibited shorter reaction times (RTs), and larger P2 and P3 amplitudes across all conditions compared to the control group. In addition, the exercise-mode differences revealed a relatively smaller specific cost, and faster motor RTs and larger P3 amplitudes, in the switch condition for the open-skill group in comparison with the closed-skill and control groups. These findings suggest that regularly participating in physical exercise can enhance behavioral and electrophysiological performance with regard to executive control in the elderly, and provide further evidence for the beneficial effects of open-skill exercise on the task-switching paradigm.

  1. Exercise-mode-related changes in task-switching performance in the elderly

    PubMed Central

    Tsai, Chia-Liang; Wang, Wen-Liang

    2015-01-01

    The objective of the current study was to explore the relationships between exercise modes and executive functions in the elderly. Twenty-one elderly individuals in the open-skill group, 22 in the closed-skill group, and 21 in the sedentary-behavior (control) group were recruited in the current study, and performed a task-switching paradigm during which the switches occurred unpredictably and infrequently, while the behavioral and electrophysiological performances were assessed simultaneously. The results indicated that although there were no group differences in accuracy rates, the two exercise groups exhibited shorter reaction times (RTs), and larger P2 and P3 amplitudes across all conditions compared to the control group. In addition, the exercise-mode differences revealed a relatively smaller specific cost, and faster motor RTs and larger P3 amplitudes, in the switch condition for the open-skill group in comparison with the closed-skill and control groups. These findings suggest that regularly participating in physical exercise can enhance behavioral and electrophysiological performance with regard to executive control in the elderly, and provide further evidence for the beneficial effects of open-skill exercise on the task-switching paradigm. PMID:25798097

  2. High Resolution Switching Mode Inductance-to-Frequency Converter with Temperature Compensationti

    PubMed Central

    Matko, Vojko; Milanović, Miro

    2014-01-01

    This article proposes a novel method for the temperature-compensated inductance-to-frequency converter with a single quartz crystal oscillating in the switching oscillating circuit to achieve better temperature stability of the converter. The novelty of this method lies in the switching-mode converter, the use of additionally connected impedances in parallel to the shunt capacitances of the quartz crystal, and two inductances in series to the quartz crystal. This brings a considerable reduction of the temperature influence of AT-cut crystal frequency change in the temperature range between 10 and 40 °C. The oscillator switching method and the switching impedances connected to the quartz crystal do not only compensate for the crystal's natural temperature characteristics but also any other influences on the crystal such as ageing as well as from other oscillating circuit elements. In addition, the method also improves frequency sensitivity in inductance measurements. The experimental results show that through high temperature compensation improvement of the quartz crystal characteristics, this switching method theoretically enables a 2 pH resolution. It converts inductance to frequency in the range of 85–100 μH to 2–560 kHz. PMID:25325334

  3. High resolution switching mode inductance-to-frequency converter with temperature compensation.

    PubMed

    Matko, Vojko; Milanović, Miro

    2014-10-16

    This article proposes a novel method for the temperature-compensated inductance-to-frequency converter with a single quartz crystal oscillating in the switching oscillating circuit to achieve better temperature stability of the converter. The novelty of this method lies in the switching-mode converter, the use of additionally connected impedances in parallel to the shunt capacitances of the quartz crystal, and two inductances in series to the quartz crystal. This brings a considerable reduction of the temperature influence of AT-cut crystal frequency change in the temperature range between 10 and 40 °C. The oscillator switching method and the switching impedances connected to the quartz crystal do not only compensate for the crystal's natural temperature characteristics but also any other influences on the crystal such as ageing as well as from other oscillating circuit elements. In addition, the method also improves frequency sensitivity in inductance measurements. The experimental results show that through high temperature compensation improvement of the quartz crystal characteristics, this switching method theoretically enables a 2 pH resolution. It converts inductance to frequency in the range of 85-100 µH to 2-560 kHz.

  4. Q-switched mode-locking of an erbium-doped fiber laser using cavity modulation frequency detuning.

    PubMed

    Chang, You Min; Lee, Junsu; Jhon, Young Min; Lee, Ju Han

    2012-07-20

    We present the results of an investigation regarding a Q-switched mode-locked fiber laser scheme based on a cavity modulation frequency detuning technique. The approach is based on undamped laser relaxation oscillations occurring due to frequency detuning in the fundamental cavity resonance frequency. Through a range of experiments with an erbium-doped, fiber-based, ring-cavity laser, this approach has been shown to be capable of generating high-quality Q-switched mode-locked pulses from an optical fiber-based laser. The maximum frequency detuning range for a stable Q-switched mode-locking operation has been observed to vary depending on the pump power used. We found that the highest pulse peak power was obtained at the frequency detuning threshold at which the operation changed from the mode-locking to the Q-switched mode-locking regime.

  5. Burst-mode gain switched technique for high peak and average optical energy extraction.

    PubMed

    Nikumb, S K; Seguin, H J; Seguin, V A; Willis, R J; Cheng, Z; Reshef, H

    1989-05-01

    The optical performance of a cw PIE CO(2) laser has been substantially improved through the adoption of a burst-mode gain switching technique. The approach has provided a doubling of the average beam power extractable from the device. With appropriate optimization, the process could possibly permit the attainment of pulsed energy extraction in the kilohertz range, and with average optical powers within the several tens of kilowatt category.

  6. Integrated-optical Q -switch/mode locker for a Nd sup 3+ fiber laser

    SciTech Connect

    Geister, G.; Ulrich, R. )

    1990-02-05

    An electro-optic phase modulator and a switched directional coupler are integrated on a common LiNbO{sub 3} substrate and inserted into the cavity of a 3-m-long Nd{sup 3+} single-mode fiber laser ({lambda}{approx}1088 nm). Their simultaneous operation yields groups of {approx}10 pulses at rates up to 2 kHz, with 50 ps pulse duration, 30 ns separation, and 200 W peak power.

  7. Evaluation of polarization mode dispersion in a telecommunication wavelength selective switch using quantum interferometry.

    PubMed

    Fraine, A; Minaeva, O; Simon, D S; Egorov, R; Sergienko, A V

    2012-01-30

    A polarization mode dispersion (PMD) measurement of a commercial telecommunication wavelength selective switch (WSS) using a quantum interferometric technique with polarization-entangled states is presented. Polarization-entangled photons with a broad spectral width covering the telecom band are produced using a chirped periodically poled nonlinear crystal. The first demonstration of a quantum metrology application using an industrial commercial device shows a promising future for practical high-resolution quantum interference.

  8. Polarization switch of four-wave mixing in large mode area hybrid photonic crystal fibers.

    PubMed

    Petersen, Sidsel R; Alkeskjold, Thomas T; Olausson, Christina B; Lægsgaard, Jesper

    2015-02-15

    Degenerate spontaneous four-wave mixing is considered in a large mode area hybrid photonic crystal fiber. Numerical and experimental results show birefringence assisted four-wave mixing for a certain polarization state of the pump field. The parametric gain can be turned on and off by switching the polarization state of the pump field between the two principal axis of the hybrid photonic crystal fiber.

  9. Spontaneous mode switching in coupled oscillators competing for constant amounts of resources

    NASA Astrophysics Data System (ADS)

    Hirata, Yoshito; Aono, Masashi; Hara, Masahiko; Aihara, Kazuyuki

    2010-03-01

    We propose a widely applicable scheme of coupling that models competitions among dynamical systems for fixed amounts of resources. Two oscillators coupled in this way synchronize in antiphase. Three oscillators coupled circularly show a number of oscillation modes such as rotation and partially in-phase synchronization. Intriguingly, simple oscillators in the model also produce complex behavior such as spontaneous switching among different modes. The dynamics reproduces well the spatiotemporal oscillatory behavior of a true slime mold Physarum, which is capable of computational optimization.

  10. Spontaneous mode switching in coupled oscillators competing for constant amounts of resources.

    PubMed

    Hirata, Yoshito; Aono, Masashi; Hara, Masahiko; Aihara, Kazuyuki

    2010-03-01

    We propose a widely applicable scheme of coupling that models competitions among dynamical systems for fixed amounts of resources. Two oscillators coupled in this way synchronize in antiphase. Three oscillators coupled circularly show a number of oscillation modes such as rotation and partially in-phase synchronization. Intriguingly, simple oscillators in the model also produce complex behavior such as spontaneous switching among different modes. The dynamics reproduces well the spatiotemporal oscillatory behavior of a true slime mold Physarum, which is capable of computational optimization.

  11. Integrated photonic emitter with a wide switching range of orbital angular momentum modes

    PubMed Central

    Wang, Yu; Zhao, Peng; Feng, Xue; Xu, Yuntao; Cui, Kaiyu; Liu, Fang; Zhang, Wei; Huang, Yidong

    2016-01-01

    Due to the nature of infinite dimensionality, the orbital angular momentum (OAM) has been considered as a new degree of freedom of light and widely expanded the scopes of substantial optical applications such as optical telecommunication, quantum information, particle manipulation and imaging. In recent years, the integrated photonic OAM emitters have been actively investigated due to both compactness and tunability. Essentially, the number of available OAM modes by dynamic switching should be large enough so that the dimensionality of OAM could be explored as much as possible. In this work, an integrated photonic emitter with a wide switching range of OAM modes is theoretically developed, numerically simulated, and experimentally verified. The independence of the micro-ring cavity and the scattering unit provides the flexibility to design the device and optimize the performance. Specifically, the dynamic switching of nine OAM modes (l = −4 ~ 4) with azimuthal polarization has been demonstrated by electrically controlled thermo-optic effect. PMID:26936327

  12. Synchronizable Q-switched, mode-locked, and cavity-dumped ruby laser for plasma diagnostics

    NASA Astrophysics Data System (ADS)

    Houtman, H.; Meyer, J.

    1985-06-01

    We report on the design and operation of an optimized version of a Q-switched, mode-locked, and cavity-dumped ruby-laser oscillator. The modulator window is much narrower than that assumed in conventional active mode-lock theory, and is shown to yield much shorter pulses than the latter in cases where the number of round trips is restricted. To allow a high-power pulse (≊1 GW) to evolve in the oscillator, and to allow simple synchronization to a (˜100 ns fixed delay) CO2 laser, a limit of 23 round trips was chosen, but similar limits may be imposed by lasers having short-gain duration as in an excimer laser. Details are given on the single spark gap switching element and Pockels cells, with an analysis of their expected switching speeds, in order to establish the effectiveness of the modulator, as compared to conventional sinusoidally driven active mode lockers. Single pulses of 50-70 mJ are reliably cavity-dumped after only 100-ns delay (23 round trips) with pulse length adjustable from 50-100 ps with ±5-ps stability. Relative timing between the main (CO2) and probe (ruby) pulses allows a measurement accuracy of ±50 ps to be attained.

  13. An on-die ultra-low voltage DC-DC step-up converter with voltage doubling LC-tank

    NASA Astrophysics Data System (ADS)

    Jayaweera, H. M. P. C.; Pathirana, W. P. M. R.; Muhtaroğlu, Ali

    2016-12-01

    In this paper we report the design, characterization and verification of a novel on-die ultra-low voltage DC-DC converter circuit for energy harvester applications in 0.18 µm complementary metal oxide semiconductor technology. The circuit self-starts, does not use off-chip components, and is thus suitable for use in highly integrated low cost systems. The first version of the design has a five-stage charge-pump stimulated by an oscillator with two center-tap inductors. It is validated on a test chip that this converter can boost 0.25 V-1.7 V for a 60 kΩ load with 15.5% maximum efficiency. The center-tap implementation leads to a 38% area reduction compared to the conventional four planar inductors. The proposed second version of the DC-DC design has a modified LC-tank with center-tap and planar hybrid inductors, which leads to a simulated step up from 0.2 V input to 1.65 V output for a 45 kΩ load with 35% maximum efficiency. The new boost implementation is hence expected to improve both power efficiency and output power capacity significantly compared to the first design, at a cost of a 31% layout area growth. The second revision in addition provides a 15% chip area reduction compared to the conventional four planar-inductor approach.

  14. Experimental research of heavy ion and proton induced single event effects for a Bi-CMOS technology DC/DC converter

    NASA Astrophysics Data System (ADS)

    Anlin, He; Gang, Guo; Shuting, Shi; Dongjun, Shen; Jiancheng, Liu; Li, Cai; Hui, Fan

    2015-11-01

    This paper tested and analyzed heavy ion and proton induced single event effects (SEE) of a commercial DC/DC converter based on a 600 nm Bi-CMOS technology. Heavy ion induced single event transients (SET) testing has been carried out by using the Beijing HI-13 tandem accelerator at China Institute of Atomic Energy. Proton test has been carried out by using the Canadian TRIUMF proton accelerator. Both SET cross section versus linear energy transfer (LET) and proton energy has been measured. The main study conclusions are: (1) the DC/DC is both sensitive to heavy ion and proton radiations although at a pretty large feature size (600 nm), and threshold LET is about 0.06 MeV·mg/cm2 (2) heavy ion SET saturation cross section is about 5 magnitudes order larger than proton SET saturation cross section, which is consistent with the theory calculation result deduced by the RPP model and the proton nuclear reaction model; (3) on-orbit soft error rate (SER) prediction showed, on GEO orbit, proton induced SERs calculated by the heavy ion derived model are 4-5 times larger than those calculated by proton test data.

  15. Modeling structural features of pulse timing jitter in a single-mode, Q-switched, Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Martin, Graham; Siemers, Troy J.; Thompson, John R.

    2017-08-01

    Timing jitter in single-mode, Q-switched pulses is measured for a repetitively Q-switched Nd:YAG laser, and the fluctuations in peak times are observed to have distinctive structural features that we model using rate equations with noise sources acting on different time scales. The structural features are found to be a consequence of the interplay of Q-switching dynamics and stochastic and deterministic parameter fluctuations.

  16. Bidirectional Control of Generalized Epilepsy Networks via Rapid Real-Time Switching of Firing Mode.

    PubMed

    Sorokin, Jordan M; Davidson, Thomas J; Frechette, Eric; Abramian, Armen M; Deisseroth, Karl; Huguenard, John R; Paz, Jeanne T

    2017-01-04

    Thalamic relay neurons have well-characterized dual firing modes: bursting and tonic spiking. Studies in brain slices have led to a model in which rhythmic synchronized spiking (phasic firing) in a population of relay neurons leads to hyper-synchronous oscillatory cortico-thalamo-cortical rhythms that result in absence seizures. This model suggests that blocking thalamocortical phasic firing would treat absence seizures. However, recent in vivo studies in anesthetized animals have questioned this simple model. Here we resolve this issue by developing a real-time, mode-switching approach to drive thalamocortical neurons into or out of a phasic firing mode in two freely behaving genetic rodent models of absence epilepsy. Toggling between phasic and tonic firing in thalamocortical neurons launched and aborted absence seizures, respectively. Thus, a synchronous thalamocortical phasic firing state is required for absence seizures, and switching to tonic firing rapidly halts absences. This approach should be useful for modulating other networks that have mode-dependent behaviors.

  17. Photonic switched beamformer implementation for broadband wireless access in transmission and reception modes at 42.7 GHz

    NASA Astrophysics Data System (ADS)

    Piqueras, Miguel A.; Vidal, Borja; Herrera, Javier; Polo, Valentín; Corral, Juan. L.; Martí, Javier

    2005-05-01

    The performance of a 3-bit photonic switched beamformer for phased array antennas based on optical switches and dispersive media is experimentally demonstrated at 42.7 GHz. Both transmission and reception modes have been experimentally tested. Broadband data transmission and radiation pattern measurements are presented.

  18. Pyrene-based dual-mode fluorescence switches and logic gates that function in solution and film.

    PubMed

    Zhou, Weidong; Li, Yongjun; Li, Yuliang; Liu, Huibiao; Wang, Shu; Li, Cuihong; Yuan, Mingjian; Liu, Xiaofeng; Zhu, Daoben

    2006-07-17

    A dual-mode fluorescence switch controlled by external inputs such as protons and metal ions is described, and each state corresponds to a specific fluorescent emission peak. Based on the reversible changes of the fluorescence emission of the switch responding to different external stimuli, the corresponding integrated logic gates and communication networks have been constructed in solid film or in solution.

  19. Single Longitudinal Mode, High Repetition Rate, Q-switched Ho:YLF Laser for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Bai, Yingxin; Yu, Jirong; Petzar, Paul; Petros, M.; Chen, Songsheng; Trieu, Bo; Lee, Nyung; Singh, U.

    2009-01-01

    Ho:YLF/LuLiF lasers have specific applications for remote sensing such as wind-speed measurement and carbon dioxide (CO2) concentration measurement in the atmosphere because the operating wavelength (around 2 m) is located in the eye-safe range and can be tuned to the characteristic lines of CO2 absorption and there is strong backward scattering signal from aerosol (Mie scattering). Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of with a repetition rate of 5 Hz and pulse energy of 75 mJ [1]. For highly precise CO2 measurements with coherent detection technique, a laser with high repetition rate is required to averaging out the speckle effect [2]. In addition, laser efficiency is critically important for the air/space borne lidar applications, because of the limited power supply. A diode pumped Ho:Tm:YLF laser is difficult to efficiently operate in high repetition rate due to the large heat loading and up-conversion. However, a Tm:fiber laser pumped Ho:YLF laser with low heat loading can be operated at high repetition rates efficiently [3]. No matter whether wind-speed or carbon dioxide (CO2) concentration measurement is the goal, a Ho:YLF/LuLiF laser as the transmitter should operate in a single longitudinal mode. Injection seeding is a valid technique for a Q-switched laser to obtain single longitudinal mode operation. In this paper, we will report the new results for a single longitudinal mode, high repetition rate, Q-switched Ho:YLF laser. In order to avoid spectral hole burning and make injection seeding easier, a four mirror ring cavity is designed for single longitudinal mode, high repetition rate Q-switched Ho:YLF laser. The ramp-fire technique is chosen for injection seeding.

  20. Single Longitudinal Mode, High Repetition Rate, Q-switched Ho:YLF Laser for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Bai, Yingxin; Yu, Jirong; Petzar, Paul; Petros, M.; Chen, Songsheng; Trieu, Bo; Lee, Nyung; Singh, U.

    2009-01-01

    Ho:YLF/LuLiF lasers have specific applications for remote sensing such as wind-speed measurement and carbon dioxide (CO2) concentration measurement in the atmosphere because the operating wavelength (around 2 m) is located in the eye-safe range and can be tuned to the characteristic lines of CO2 absorption and there is strong backward scattering signal from aerosol (Mie scattering). Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of with a repetition rate of 5 Hz and pulse energy of 75 mJ [1]. For highly precise CO2 measurements with coherent detection technique, a laser with high repetition rate is required to averaging out the speckle effect [2]. In addition, laser efficiency is critically important for the air/space borne lidar applications, because of the limited power supply. A diode pumped Ho:Tm:YLF laser is difficult to efficiently operate in high repetition rate due to the large heat loading and up-conversion. However, a Tm:fiber laser pumped Ho:YLF laser with low heat loading can be operated at high repetition rates efficiently [3]. No matter whether wind-speed or carbon dioxide (CO2) concentration measurement is the goal, a Ho:YLF/LuLiF laser as the transmitter should operate in a single longitudinal mode. Injection seeding is a valid technique for a Q-switched laser to obtain single longitudinal mode operation. In this paper, we will report the new results for a single longitudinal mode, high repetition rate, Q-switched Ho:YLF laser. In order to avoid spectral hole burning and make injection seeding easier, a four mirror ring cavity is designed for single longitudinal mode, high repetition rate Q-switched Ho:YLF laser. The ramp-fire technique is chosen for injection seeding.

  1. A high repetition rate passively Q-switched microchip laser for controllable transverse laser modes

    NASA Astrophysics Data System (ADS)

    Dong, Jun; Bai, Sheng-Chuang; Liu, Sheng-Hui; Ueda, Ken-Ichi; Kaminskii, Alexander A.

    2016-05-01

    A Cr4+:YAG passively Q-switched Nd:YVO4 microchip laser for versatile controllable transverse laser modes has been demonstrated by adjusting the position of the Nd:YVO4 crystal along the tilted pump beam direction. The pump beam diameter-dependent asymmetric saturated inversion population inside the Nd:YVO4 crystal governs the oscillation of various Laguerre-Gaussian, Ince-Gaussian and Hermite-Gaussian modes. Controllable transverse laser modes with repetition rates over 25 kHz and up to 183 kHz, depending on the position of the Nd:YVO4 crystal, have been achieved. The controllable transverse laser beams with a nanosecond pulse width and peak power over hundreds of watts have been obtained for potential applications in optical trapping and quantum computation.

  2. Synchronous x-ray and radio mode switches: a rapid global transformation of the pulsar magnetosphere.

    PubMed

    Hermsen, W; Hessels, J W T; Kuiper, L; van Leeuwen, J; Mitra, D; de Plaa, J; Rankin, J M; Stappers, B W; Wright, G A E; Basu, R; Alexov, A; Coenen, T; Grießmeier, J-M; Hassall, T E; Karastergiou, A; Keane, E; Kondratiev, V I; Kramer, M; Kuniyoshi, M; Noutsos, A; Serylak, M; Pilia, M; Sobey, C; Weltevrede, P; Zagkouris, K; Asgekar, A; Avruch, I M; Batejat, F; Bell, M E; Bell, M R; Bentum, M J; Bernardi, G; Best, P; Bîrzan, L; Bonafede, A; Breitling, F; Broderick, J; Brüggen, M; Butcher, H R; Ciardi, B; Duscha, S; Eislöffel, J; Falcke, H; Fender, R; Ferrari, C; Frieswijk, W; Garrett, M A; de Gasperin, F; de Geus, E; Gunst, A W; Heald, G; Hoeft, M; Horneffer, A; Iacobelli, M; Kuper, G; Maat, P; Macario, G; Markoff, S; McKean, J P; Mevius, M; Miller-Jones, J C A; Morganti, R; Munk, H; Orrú, E; Paas, H; Pandey-Pommier, M; Pandey, V N; Pizzo, R; Polatidis, A G; Rawlings, S; Reich, W; Röttgering, H; Scaife, A M M; Schoenmakers, A; Shulevski, A; Sluman, J; Steinmetz, M; Tagger, M; Tang, Y; Tasse, C; ter Veen, S; Vermeulen, R; van de Brink, R H; van Weeren, R J; Wijers, R A M J; Wise, M W; Wucknitz, O; Yatawatta, S; Zarka, P

    2013-01-25

    Pulsars emit from low-frequency radio waves up to high-energy gamma-rays, generated anywhere from the stellar surface out to the edge of the magnetosphere. Detecting correlated mode changes across the electromagnetic spectrum is therefore key to understanding the physical relationship among the emission sites. Through simultaneous observations, we detected synchronous switching in the radio and x-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio-"bright" mode, the x-rays show only an unpulsed, nonthermal component. Conversely, when the pulsar is in a radio-"quiet" mode, the x-ray luminosity more than doubles and a 100% pulsed thermal component is observed along with the nonthermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories.

  3. Influence of material anisotropy in the switching toggle mode in MRAM devices

    NASA Astrophysics Data System (ADS)

    Olariu, Cristina Stefania; Stoleriu, Laurentiu; Stancu, Alexandru

    2007-09-01

    In the development of magneto-resistance random access memory (MRAM), the theoretical studies are now concentrated in various parameters improving. Some important parameters are the range of the operating field and the switching time. The analysis presented in this paper is concentrated to a synthetic antiferromagnet (SAF). Recently a considerable effort has been expended by Fujiwara and co-workers to the analysis of the switching mode suggested by Savtchenko et al., called also toggle MRAM, and a number of conditions were found to maximize the operating field margin; most of these studies were based on a critical-curve approach. For uniaxial anisotropy, an analytical approach is possible and simple results and critical curves are presented. For the more general case, only the micromagnetic simulation can offer results. The studies are made for different coupling constants between the two ferromagnetic layers and the results are discussed.

  4. Control system of mutually coupled switched reluctance motor drive of mining machines in generator mode

    NASA Astrophysics Data System (ADS)

    Ivanov, A. S.; Kalanchin, I. Yu; Pugacheva, E. E.

    2017-09-01

    One of the first electric motors, based on the use of electromagnets, was a reluctance motor in the XIX century. Due to the complexities in the implementation of control system the development of switched reluctance electric machines was repeatedly initiated only in 1960 thanks to the development of computers and power electronic devices. The main feature of these machines is the capacity to work both in engine mode and in generator mode. Thanks to a simple and reliable design in which there is no winding of the rotor, commutator, permanent magnets, a reactive gate-inductor electric drive operating in the engine mode is actively being introduced into various areas such as car industry, production of household appliances, wind power engineering, as well as responsible production processes in the oil and mining industries. However, the existing shortcomings of switched reluctance electric machines, such as nonlinear pulsations of electromagnetic moment, the presence of three or four phase supply system and sensor of rotor position prevent wide distribution of this kind of electric machines.

  5. 1400, +/- 900V PEAK PULSE SWITCH MODE POWER SUPPLIES FOR SNS INJECTION KICKERS.

    SciTech Connect

    LAMBIASE,R.ENG,W.SANDBERG,J.DEWAN,S.HOLMES,R.RUST,K.ZENG,J.

    2004-03-10

    This paper describes simulation and experimental results for a 1400A, {+-} 900V peak rated, switch mode power supply for SNS Injection Kicker Magnets. For each magnet (13 m{Omega}, 160{micro}H), the power supply must supply controlled pulses at 60 Hz repetition rate. The pulse current must rise from zero to maximum in less than 1 millisec in a controlled manner, flat top for up to 2 millisec, and should fall in a controlled manner to less than 4A within 500{micro}s. The low current performance during fall time is the biggest challenge in this power supply. The simulation results show that to meet the controlled fall of the current and the current ripple requirements, voltage loop bandwidth of at least 10 kHz and switching frequency of at least 100 kHz are required. To achieve high power high frequency switching with IGBT switches, a series connected topology with three phase shifted (O{sup o}, 60{sup o} & 120{sup o}) converters each with 40 kHz switching frequency (IGBT at 20kHz), has been achieved. In this paper, the circuit topology, relevant system specifications and experimental results that meet the requirements of the power supply are described in detail. A unique six pulse SCR rectifier circuit with capacitor storage has been implemented to achieve minimum pulse width to meet required performance during current fall time below 50A due to the very narrow pulse width and non-linearity from IGBT turn-on/off times.

  6. The N Terminus Specifies the Switch between Transport Modes of the Human Serotonin Transporter*

    PubMed Central

    Kern, Carina; Erdem, Fatma Asli; El-Kasaby, Ali; Sandtner, Walter; Freissmuth, Michael; Sucic, Sonja

    2017-01-01

    The serotonin transporter (SERT) and other monoamine transporters operate in either a forward transport mode where the transporter undergoes a full transport cycle or an exchange mode where the transporter seesaws through half-cycles. Amphetamines trigger the exchange mode, leading to substrate efflux. This efflux was proposed to rely on the N terminus, which was suggested to adopt different conformations in the inward facing, outward facing and amphetamine-bound states. This prediction was verified by tryptic digestion of SERT-expressing membranes: in the absence of Na+, the N terminus was rapidly digested. Amphetamine conferred protection against cleavage, suggesting a relay between the conformational states of the hydrophobic core and the N terminus. We searched for a candidate segment that supported the conformational switch by serial truncation removing 22 (ΔN22), 32 (ΔN32), or 42 (ΔN42) N-terminal residues. This did not affect surface expression, inhibitor binding, and substrate influx. However, amphetamine-induced efflux by SERT-ΔN32 or SERT-ΔN42 (but not by SERT-ΔN22) was markedly diminished. We examined the individual steps in the transport cycle by recording transporter-associated currents: the recovery rate of capacitive peak, but not of steady state, currents was significantly lower for SERT-ΔN32 than that of wild type SERT and SERT-ΔN22. Thus, the exchange mode of SERT-ΔN32 was selectively impaired. Our observations show that the N terminus affords the switch between transport modes. The findings are consistent with a model where the N terminus acts as a lever to support amphetamine-induced efflux by SERT. PMID:28104804

  7. Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

    NASA Astrophysics Data System (ADS)

    Molli, Giancarlo; Menegon, Luca; Malasoma, Alessandro

    2017-07-01

    The switching in deformation mode (from distributed to localized) and mechanisms (viscous versus frictional) represent a relevant issue in the frame of crustal deformation, being also connected with the concept of the brittle-ductile transition and seismogenesis. In a subduction environment, switching in deformation mode and mechanisms and scale of localization may be inferred along the subduction interface, in a transition zone between the highly coupled (seismogenic zone) and decoupled deeper aseismic domain (stable slip). However, the role of brittle precursors in nucleating crystal-plastic shear zones has received more and more consideration being now recognized as fundamental in some cases for the localization of deformation and shear zone development, thus representing a case in which switching deformation mechanisms and scale and style of localization (deformation mode) interact and relate to each other. This contribution analyses an example of a millimetre-scale shear zone localized by brittle precursor formed within a host granitic protomylonite. The studied structures, developed in ambient pressure-temperature (P-T) conditions of low-grade blueschist facies (temperature T of ca. 300 °C and pressure P ≥ 0. 70 GPa) during involvement of Corsican continental crust in the Alpine subduction. We used a multidisciplinary approach by combining detailed microstructural and petrographic analyses, crystallographic preferred orientation by electron backscatter diffraction (EBSD), and palaeopiezometric studies on a selected sample to support an evolutionary model and deformation path for subducted continental crust. We infer that the studied structures, possibly formed by transient instability associated with fluctuations of pore fluid pressure and episodic strain rate variations, may be considered as a small-scale example of fault behaviour associated with a cycle of interseismic creep and coseismic rupture or a new analogue for episodic tremors and slow

  8. Passively Q-switched and mode-locked Nd:YVO4 laser with sandwich structured wallpaper graphene oxide absorber

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Wang, Y. G.; Yu, H. J.; Sun, W.; Han, Z. H.; Zhang, S. B.; Hou, W.; Lin, X. C.; Li, J. M.; Tang, J.

    2011-11-01

    We report on a passively Q-switched and mode-locked Nd:YVO4 laser using a novel low-cost wallpaper graphene oxide absorber. Sandwich structured wallpaper graphene oxide absorber was constructed by a high transmission mirror, a piece of wallpaper graphene oxide absorber and a reflective mirror. The average output power of 310 mW of passively Q-switched and mode-locked laser was successfully achieved. The repetition rate and pulse width of the Q-switched envelope were 213 kHz and 770 ns, respectively. The repetition rate of passively mode-locked pulse within the Q-switched envelope was 81.3 MHz with the pulse energy of 3.8 nJ.

  9. Electro- and magneto-optical switching of defect modes in one- dimensional photonic crystals

    SciTech Connect

    Arkhipkin, V. G.; Gunyakov, V. A. Myslivets, S. A.; Zyryanov, V. Ya.; Shabanov, V. F.; Lee Wei

    2011-04-15

    The transmission spectra of polarized light waves in a photonic crystal/liquid crystal (PC/LC) cell placed between crossed polarizers and controlled by an electric or magnetic field have been studied experimentally and theoretically. Electro- and magneto-optical switching based on the interference of polarized defect modes has been demonstrated. The transmission spectra of the PC/LC cell have been calculated as a function of the voltage applied to the LC layer and the magnetic field strength. The results of the calculations agree well with the experimental data.

  10. Method of pedestal and common-mode noise correction for switched-capacitor analog memories

    DOEpatents

    Britton, C.L.

    1996-12-31

    A method and apparatus are disclosed for correcting common-mode noise and pedestal noise in a multichannel array of switched-capacitor analog memories wherein each analog memory is connected to an associated analog-to-digital converter. The apparatus comprises a single differential element in two different embodiments. In a first embodiment, the differential element is a reference analog memory connected to a buffer. In the second embodiment, the differential element is a reference analog memory connected to a reference analog-to-digital connected to an array of digital summing circuits. 4 figs.

  11. Method of pedestal and common-mode noise correction for switched-capacitor analog memories

    DOEpatents

    Britton, C.L.

    1997-09-23

    A method and apparatus are disclosed for correcting common-mode noise and pedestal noise in a multichannel array of switched-capacitor analog memories wherein each analog memory is connected to an associated analog-to-digital converter. The apparatus comprises a single differential element in two different embodiments. In a first embodiment, the differential element is a reference analog memory connected to a buffer. In the second embodiment, the differential dement is a reference analog memory connected to a reference analog-to-digital connected to an array of digital summing circuits. 4 figs.

  12. Graph-Switching Based Modeling of Mode Transition Constraints for Model Predictive Control of Hybrid Systems

    NASA Astrophysics Data System (ADS)

    Kobayashi, Koichi; Hiraishi, Kunihiko

    The model predictive/optimal control problem for hybrid systems is reduced to a mixed integer quadratic programming (MIQP) problem. However, the MIQP problem has one serious weakness, i.e., the computation time to solve the MIQP problem is too long for practical plants. For overcoming this technical issue, there are several approaches. In this paper, a modeling of mode transition constraints, which are expressed by a directed graph, is focused, and a new method to represent a directed graph is proposed. The effectiveness of the proposed method is shown by numerical examples on linear switched systems and piecewise linear systems.

  13. Method of pedestal and common-mode noise correction for switched-capacitor analog memories

    DOEpatents

    Britton, Charles L.

    1997-01-01

    A method and apparatus for correcting common-mode noise and pedestal noise in a multichannel array of switched-capacitor analog memories wherein each analog memory is connected to an associated analog-to-digital converter. The apparatus comprises a single differential element in two different embodiments. In a first embodiment, the differential element is a reference analog memory connected to a buffer. In the second embodiment, the differential dement is a reference analog memory connected to a reference analog-to-digital connected to an array of digital summing circuits.

  14. Method of pedestal and common-mode noise correction for switched-capacitor analog memories

    DOEpatents

    Britton, Charles L.

    1996-01-01

    A method and apparatus for correcting common-mode noise and pedestal noise in a multichannel array of switched-capacitor analog memories wherein each analog memory is connected to an associated analog-to-digital converter. The apparatus comprises a single differential element in two different embodiments. In a first embodiment, the differential element is a reference analog memory connected to a buffer. In the second embodiment, the differential element is a reference analog memory connected to a reference analog-to-digital connected to an array of digital summing circuits.

  15. An analysis toolbox to explore mesenchymal migration heterogeneity reveals adaptive switching between distinct modes

    PubMed Central

    Shafqat-Abbasi, Hamdah; Kowalewski, Jacob M; Kiss, Alexa; Gong, Xiaowei; Hernandez-Varas, Pablo; Berge, Ulrich; Jafari-Mamaghani, Mehrdad; Lock, John G; Strömblad, Staffan

    2016-01-01

    Mesenchymal (lamellipodial) migration is heterogeneous, although whether this reflects progressive variability or discrete, 'switchable' migration modalities, remains unclear. We present an analytical toolbox, based on quantitative single-cell imaging data, to interrogate this heterogeneity. Integrating supervised behavioral classification with multivariate analyses of cell motion, membrane dynamics, cell-matrix adhesion status and F-actin organization, this toolbox here enables the detection and characterization of two quantitatively distinct mesenchymal migration modes, termed 'Continuous' and 'Discontinuous'. Quantitative mode comparisons reveal differences in cell motion, spatiotemporal coordination of membrane protrusion/retraction, and how cells within each mode reorganize with changed cell speed. These modes thus represent distinctive migratory strategies. Additional analyses illuminate the macromolecular- and cellular-scale effects of molecular targeting (fibronectin, talin, ROCK), including 'adaptive switching' between Continuous (favored at high adhesion/full contraction) and Discontinuous (low adhesion/inhibited contraction) modes. Overall, this analytical toolbox now facilitates the exploration of both spontaneous and adaptive heterogeneity in mesenchymal migration. DOI: http://dx.doi.org/10.7554/eLife.11384.001 PMID:26821527

  16. Electrochemical treatment of tannery effluent using a battery integrated DC-DC converter and solar PV power supply--an approach towards environment and energy management.

    PubMed

    Iyappan, K; Basha, C Ahmed; Saravanathamizhan, R; Vedaraman, N; Tahiyah Nou Shene, C A; Begum, S Nathira

    2014-01-01

    Electrochemical oxidation of tannery effluent was carried out in batch, batch recirculation and continuous reactor configurations under different conditions using a battery-integrated DC-DC converter and solar PV power supply. The effect of current density, electrolysis time and fluid flow rate on chemical oxygen demand (COD) removal and energy consumption has been evaluated. The results of batch reactor show that a COD reduction of 80.85% to 96.67% could be obtained. The results showed that after 7 h of operation at a current density of 2.5 A dm(-2) and flow rate of 100 L h(-1) in batch recirculation reactor, the removal of COD is 82.14% and the specific energy consumption was found to be 5.871 kWh (kg COD)(-1) for tannery effluent. In addition, the performance of single pass flow reactors (single and multiple reactors) system of various configurations are analyzed.

  17. The Radio and X-ray Mode-Switching Pulsar PSR B0943+10

    NASA Astrophysics Data System (ADS)

    Mereghetti, Sandro; Rigoselli, Michela

    2017-09-01

    Observations obtained in the last years challenged the widespread notion that rotation-powered neutron stars are steady X-ray emitters. Besides a few allegedly rotation-powered neutron stars that showed `magnetar-like' variability, a particularly interesting case is that of PSR B0943+10. Recent observations have shown that this pulsar, well studied in the radio band where it alternates between a bright and a quiescent mode, displays significant X-ray variations, anticorrelated in flux with the radio emission. The study of such synchronous radio/X-ray mode switching opens a new window to investigate the processes responsible for the pulsar radio and high-energy emission. Here we review the main X-ray properties of PSR B0943+10 derived from recent coordinated X-ray and radio observations.

  18. Promotion of protein crystal growth by actively switching crystal growth mode via femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Tominaga, Yusuke; Maruyama, Mihoko; Yoshimura, Masashi; Koizumi, Haruhiko; Tachibana, Masaru; Sugiyama, Shigeru; Adachi, Hiroaki; Tsukamoto, Katsuo; Matsumura, Hiroyoshi; Takano, Kazufumi; Murakami, Satoshi; Inoue, Tsuyoshi; Yoshikawa, Hiroshi Y.; Mori, Yusuke

    2016-11-01

    Large single crystals with desirable shapes are essential for various scientific and industrial fields, such as X-ray/neutron crystallography and crystalline devices. However, in the case of proteins the production of such crystals is particularly challenging, despite the efforts devoted to optimization of the environmental, chemical and physical parameters. Here we report an innovative approach for promoting the growth of protein crystals by directly modifying the local crystal structure via femtosecond laser ablation. We demonstrate that protein crystals with surfaces that are locally etched (several micrometers in diameter) by femtosecond laser ablation show enhanced growth rates without losing crystal quality. Optical phase-sensitive microscopy and X-ray topography imaging techniques reveal that the local etching induces spiral growth, which is energetically advantageous compared with the spontaneous two-dimensional nucleation growth mode. These findings prove that femtosecond laser ablation can actively switch the crystal growth mode, offering flexible control over the size and shape of protein crystals.

  19. A new current regulator for the APS storage ring correction magnet bipolar switching mode converters.

    SciTech Connect

    Wang, J.; Accelerator Systems Division

    2004-01-01

    The correction magnets in the Advanced Photon Source's storage ring are powered by PWM-controlled bipolar switching-mode converters. These converters are designed to operate at up to {+-}150 A. The original control circuit used a polarity detection circuit with a hysteresis to determine which IGBT was needed to regulate the current with a given polarity. Only the required IGBT was switched with PWM pulses while others were held on or off continuously. The overall IGBT switching losses were minimized by the design. The shortcoming of the design was that the converter's output was unstable near zero current because of the hysteresis. To improve the stability, a new current regulator using a different PWM method has been developed to eliminate the requirement of the polarity detection. With the new design, converters can operate smoothly in the full range of {+-}150 A. The new design also meets tighter specs in terms of the ripple current and dynamic response. This paper describes the design of the new regulator and the test results.

  20. Common mechanics of mode switching in locomotion of limbless and legged animals.

    PubMed

    Kuroda, Shigeru; Kunita, Itsuki; Tanaka, Yoshimi; Ishiguro, Akio; Kobayashi, Ryo; Nakagaki, Toshiyuki

    2014-06-06

    Crawling using muscular waves is observed in many species, including planaria, leeches, nemertea, aplysia, snails, chitons, earthworms and maggots. Contraction or extension waves propagate along the antero-posterior axis of the body as the crawler pushes the ground substratum backward. However, the observation that locomotory waves can be directed forward or backward has attracted much attention over the past hundred years. Legged organisms such as centipedes and millipedes exhibit parallel phenomena; leg tips form density waves that propagate backward or forward. Mechanical considerations reveal that leg-density waves play a similar role to locomotory waves in limbless species, and that locomotory waves are used by a mechanism common to both legged and limbless species to achieve crawling. Here, we report that both mode switching of the wave direction and friction control were achieved when backward motion was induced in the laboratory. We show that the many variations of switching in different animals can essentially be classified in two types according to mechanical considerations. We propose that during their evolution, limbless crawlers first moved in a manner similar to walking before legs were obtained. Therefore, legged crawlers might have learned the mechanical mode of movement involved in walking long before obtaining legs.

  1. Using the Virtual Heart Model to validate the mode-switch pacemaker operation.

    PubMed

    Jiang, Zhihao; Connolly, Allison; Mangharam, Rahul

    2010-01-01

    Artificial pacemakers are one of the most widely-used implantable devices today, with millions implanted worldwide. The main purpose of an artificial pacemaker is to treat bradycardia, or slow heart beats, by pacing the atrium and ventricles at a faster rate. While the basic functionality of the device is fairly simple, there are many documented cases of death and injury due to device malfunctions. The frequency of malfunctions due to firmware problems will only increase as the pacemaker operations become more complex in an attempt to expand the use of the device. One reason these malfunctions arise is that there is currently no methodology for formal validation and verification of medical device software, as there are in the safety-critical domains of avionics and industrial control automation. We have developed a timed-automata based Virtual Heart Model (VHM) to act as platform for medical device software validation and verification. Through a case study involving multiple arrhythmias, this investigation shows how the VHM can be used with closed-loop operation of a pacemaker to validate the necessity and functionality of the complex mode-switch pacemaker operation. We demonstrate the correct pacemaker operation, to switch from one rhythm management mode to another, in patients with supraventricular tachycardias. (1).

  2. Common mechanics of mode switching in locomotion of limbless and legged animals

    PubMed Central

    Kuroda, Shigeru; Kunita, Itsuki; Tanaka, Yoshimi; Ishiguro, Akio; Kobayashi, Ryo; Nakagaki, Toshiyuki

    2014-01-01

    Crawling using muscular waves is observed in many species, including planaria, leeches, nemertea, aplysia, snails, chitons, earthworms and maggots. Contraction or extension waves propagate along the antero-posterior axis of the body as the crawler pushes the ground substratum backward. However, the observation that locomotory waves can be directed forward or backward has attracted much attention over the past hundred years. Legged organisms such as centipedes and millipedes exhibit parallel phenomena; leg tips form density waves that propagate backward or forward. Mechanical considerations reveal that leg-density waves play a similar role to locomotory waves in limbless species, and that locomotory waves are used by a mechanism common to both legged and limbless species to achieve crawling. Here, we report that both mode switching of the wave direction and friction control were achieved when backward motion was induced in the laboratory. We show that the many variations of switching in different animals can essentially be classified in two types according to mechanical considerations. We propose that during their evolution, limbless crawlers first moved in a manner similar to walking before legs were obtained. Therefore, legged crawlers might have learned the mechanical mode of movement involved in walking long before obtaining legs. PMID:24718452

  3. Nonlinear mode switching in lithium niobate nanowaveguides to control light directionality.

    PubMed

    Escalé, Marc Reig; Sergeyev, Anton; Geiss, Reinhard; Grange, Rachel

    2017-02-20

    The ability of nanowaveguides to confine and guide light has been applied for developing optical applications such as nanolasers, optical switching and localized imaging. These and others applications can be further complemented by the optical control of the guided modes within the nanowaveguide, which in turn dictates the light emission pattern. It has been shown that the light directionality can be shaped by varying the nanowire cross-sections. Here, we demonstrate that the directionality of the light can be modified using a single nanowaveguide with a nonlinear phenomenon such as second-harmonic generation. In individual lithium niobate nanowaveguides, we use second-harmonic modal phase-matching and we apply it to switch the guided modes within its sub-micron cross-section. In doing so, we can vary the light directionality of the generated light from straight (0° with respect to the propagation direction) to large spread angles (almost 54°). Further, we characterize the directionality of the guided light by means of optical Fourier transformation and show that the directionality of the guided light changes for different wavelengths.

  4. Multiparameter bifurcations and mixed-mode oscillations in Q-switched CO2 lasers.

    PubMed

    Doedel, Eusebius J; Pando L, Carlos L

    2014-05-01

    We study the origin of mixed-mode oscillations and related bifurcations in a fully molecular laser model that describes CO2 monomode lasers with a slow saturable absorber. Our study indicates that the presence of isolas of periodic mixed-mode oscillations, as the pump parameter and the cavity-frequency detuning change, is inherent to Q-switched CO2 monomode lasers. We compare this model, known as the dual four-level model, to the more conventional 3:2 model and to a CO2 laser model for fast saturable absorbers. In these models, we find similarities as well as qualitative differences, such as the different nature of the homoclinic tangency to a relevant unstable periodic orbit, where the Gavrilov-Shilnikov theory and its extensions may hold. We also show that there are isolas of periodic mixed-mode oscillations in a model for CO2 lasers with modulated losses, as the pump parameter varies. The coarse-grained bifurcation diagrams of the periodic mixed-mode oscillations in these models suggest that these oscillations belong to similar classes.

  5. Model predictive control of an air suspension system with damping multi-mode switching damper based on hybrid model

    NASA Astrophysics Data System (ADS)

    Sun, Xiaoqiang; Yuan, Chaochun; Cai, Yingfeng; Wang, Shaohua; Chen, Long

    2017-09-01

    This paper presents the hybrid modeling and the model predictive control of an air suspension system with damping multi-mode switching damper. Unlike traditional damper with continuously adjustable damping, in this study, a new damper with four discrete damping modes is applied to vehicle semi-active air suspension. The new damper can achieve different damping modes by just controlling the on-off statuses of two solenoid valves, which makes its damping adjustment more efficient and more reliable. However, since the damping mode switching induces different modes of operation, the air suspension system with the new damper poses challenging hybrid control problem. To model both the continuous/discrete dynamics and the switching between different damping modes, the framework of mixed logical dynamical (MLD) systems is used to establish the system hybrid model. Based on the resulting hybrid dynamical model, the system control problem is recast as a model predictive control (MPC) problem, which allows us to optimize the switching sequences of the damping modes by taking into account the suspension performance requirements. Numerical simulations results demonstrate the efficacy of the proposed control method finally.

  6. Digitally Controlled 4-Phase Bi-Directional Interleaved Dc-Dc Converter with Coupled Inductors / Digitāli Vadāms 4 Fāžu Divvirziena Līdzstrāvas Pārveidotājs Ar Saistītajām Droselēm

    NASA Astrophysics Data System (ADS)

    Kroics, K.; Sirmelis, U.; Grigans, L.

    2015-08-01

    The main advantages of multiphase interleaved DC-DC converters over single-phase converters are reduced current stress and reduced output current ripple. Nevertheless, inductor current ripple cannot be reduced only by an interleaving method. The integrated magnetic structure can be used to solve this problem. In this paper, the application of 2-phase coupled inductor designed in a convenient way by using commercially manufactured coil formers and ferrite cores is analysed to develop a 4-phase interleaved DC-DC converter. The steady state phase and output current ripple in a boost mode of the interleaved bidirectional DC-DC converter with integrated magnetics are analysed. The prototype of the converter has been built. The experimental results of the current ripple are presented in the paper. Šajā rakstā piedāvāta magnētiski saistīta drosele, kas izveidota, izmantojot plaša patēriņa ferrīta serdi un tinuma formētāju. Izmantojot šādas droseles, var tikt izveidots vairākfāžu pārveidotājs ar mazām izejas un iejas strāvas pulsācijām, kā arī samazinātām strāvas pulsācijām droselē. Rakstā sīkāk apskatīts līdzstrāvas pārveidotājs, kas sastāv no četrām fāzēm. Šim gadījumam izvestas teorētiskās formulas strāvas pulsāciju aprēķinam, kā arī rakstā parādīti eksperimentālie rezultāti, kas iegūti, testējot prototipu. Teorētiskie rezultāti sakrīt ar eksperimentālajiem

  7. A stable polarization switching laser from a bidirectional passively mode-locked thulium-doped fiber oscillator.

    PubMed

    Zhou, Wei; Shen, Deyuan; Wang, Yishan; Ma, Hefeng; Wang, Fei

    2013-04-08

    We report on a novel polarization switching laser from a bidirectional passively mode-locked thulium(Tm)-doped fiber oscillator, which was characterized by the periodical change of polarization state of every pulse. The switching laser was created by combing two orthogonally stable vector solitons, which were found to be wave-breaking-free pulses in the all-anomalous-dispersion regime. The measured repetition rates of switching laser and the corresponding vector solitons were 49.596 MHz, 24.798 MHz, and 24.798MHz. By controlling wave plates, either of the polarized pulse trains can be switched on or off. To our knowledge, this is the first report of polarization switching laser with vector solitons in Tm fiber oscillators.

  8. Clinical efficacy of the dual-pulsed Q-switched neodymium:yttrium-aluminum-garnet laser: Comparison with conservative mode.

    PubMed

    Kim, Byung Wook; Lee, Mi Hye; Chang, Sung Eun; Yun, Woo Jin; Won, Chong Hyun; Lee, Mi Woo; Choi, Jee Ho; Moon, Kee Chan

    2013-12-01

    The quality (Q)-switched neodymium:yttrium-aluminum-garnet (Nd:YAG) laser is one of the first non-ablative lasers to be used for facial resurfacing and photorejuvenation. Recently, the method of low-fluence Q-switched Nd:YAG lasers known as 'laser toning' has been used for non-ablative skin rejuvenation and for the treatment of melasma in Asian countries. We report our experience of using a novel Q-switched Nd:YAG laser that was operated as a dual pulse at half fluence and 140-μs intervals compared with conservative mode laser.

  9. Structure of picosecond pulses of a Q-switched and mode-locked diode-pumped Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Donin, V. I.; Yakovin, D. V.; Gribanov, A. V.

    2015-12-01

    The pulse duration of a diode-pumped Nd:YAG laser, in which Q-switching with mode-locking (QML regime) is achieved using a spherical mirror and a travelling-wave acousto-optic modulator, is directly measured with a streak camera. It is found that the picosecond pulses can have a non-single-pulse structure, which is explained by excitation of several competing transverse modes in the Q-switching regime with a pulse repetition rate of 1 kHz. In the case of cw mode-locking (without Q-switching), a new (auto-QML) regime is observed, in which the pulse train repetition rate is determined by the frequency of the relaxation oscillations of the laser field while the train contains single picosecond pulses.

  10. Structure of picosecond pulses of a Q-switched and mode-locked diode-pumped Nd:YAG laser

    SciTech Connect

    Donin, V I; Yakovin, D V; Gribanov, A V

    2015-12-31

    The pulse duration of a diode-pumped Nd:YAG laser, in which Q-switching with mode-locking (QML regime) is achieved using a spherical mirror and a travelling-wave acousto-optic modulator, is directly measured with a streak camera. It is found that the picosecond pulses can have a non-single-pulse structure, which is explained by excitation of several competing transverse modes in the Q-switching regime with a pulse repetition rate of 1 kHz. In the case of cw mode-locking (without Q-switching), a new (auto-QML) regime is observed, in which the pulse train repetition rate is determined by the frequency of the relaxation oscillations of the laser field while the train contains single picosecond pulses. (control of laser radiation parameters)

  11. Efficient AlGaN/GaN Linear and Digital-Switch-Mode Power Amplifiers for Operation at 2GHz

    NASA Astrophysics Data System (ADS)

    Maroldt, Stephan; Wiegner, Dirk; Vitanov, Stanislav; Palankovski, Vassil; Quay, Rüdiger; Ambacher, Oliver

    This work addresses the enormous efficiency and linearity potential of optimized AlGaN/GaN high-electron mobility transistors (HEMT) in conventional Doherty linear base-station amplifiers at 2.7GHz. Supported by physical device simulation, the work further elaborates on the use of AlGaN/GaN HEMTs in high-speed current-switch-mode class-D (CMCD)/class-S MMICs for data rates of up to 8Gbit/s equivalent to 2GHz RF-operation. The device needs for switch-mode operation are derived and verified by MMIC results in class-S and class-D operation. To the authors' knowledge, this is the first time 2GHz-equivalent digital-switch-mode RF-operation is demonstrated with GaN HEMTs with high efficiency.

  12. How to test mode switching in pacemakers implanted in patients: the MOST study.

    PubMed

    Padeletti, Luigi; Gasparini, Maurizio; Porciani, Maria Cristina; Pieragnoli, Paolo; Colella, Andrea; Michelucci, Antonio; Proclemer, Alessandro; Tognarini, Stefano; Mantica, Massimo; Coltorti, Fernando; Corbucci, Giorgio; Sutton, Richard

    2002-02-01

    Optimal management of atrial arrhythmias with dual chamber pacemakers requires proper performance of automatic mode switching (AMS). The aim of this study was to develop a reliable technique to test the AMS function by using an external electronic device capable of mimicking the occurrence of supraventricular arrhythmias (Supraventricular Arrhythmia Simulator [SAS]). The SAS delivers low voltage pulse trains (200 mV, 20 ms) through two skin electrodes. Each pulse train lasts 15 seconds and starts synchronously with a pacing pulse of the implanted pacemaker to avoid interference from the operator. The pulse train rate is set at 350, 250, and 160 beats/min to simulate AF, atrial flutter, and atrial tachycardia (AT), respectively. Thirty-five patients implanted with Vitatron pacemakers, whose AMS system has been previously validated, were enrolled. Atrial and ventricular sensing were programmed in unipolar mode at 0.5 mV and in bipolar mode at > 2 mV, respectively. All pulses from the SAS were detected by the atrial channel at an amplitude ranging from 1 to 3 mV. The test proved to be safe and reliable at rest and during exercise. AMS occurred immediately at onset or at offset of atrial arrhythmias, and no adverse interference on pacemaker function was seen from the SAS. In conclusion, the described technique and the SAS are safe and reliable for patient and pacemaker function and can be proposed as a useful method to verify proper performance of AMS function irrespective of the type of implanted devices.

  13. Passively Q-switched Single-longitudinal-mode c-cut Nd:GdVO4 laser with a twisted-mode cavity.

    PubMed

    Pan, Haifeng; Xu, Shixiang; Zeng, Heping

    2005-04-04

    Single-longitudinal-mode operation is achieved in a twisted-mode-cavity c-cut Nd:GdVO4 laser. With a semiconductor saturable absorption mirror as an intracavity saturable absorber to launch passive Q-switching, no mode-locked spikes are observed on the temporal envelopes of the Q-switched output pulses due to the complete elimination of spatial hole burning in the gain medium to suppress longitudinal multi-modes. The maximal average output power is 1.24 W with the repetition rate of 76.3 kHz, and the single pulse energy is 16.0 microJ. The pulse width and polarization ratio of the output laser beam are measured about 150 ns and 53:1, respectively.

  14. LD-pumped acousto-optical Q-switched burst-mode Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Pan, Hu; Yan, Renpeng; Li, Xudong; Ma, Yufei; Yu, Xin; Chen, Deying

    2016-04-01

    A high-repetition-rate, high-peak-power burst-mode laser for laser-based measurement applications is presented by using a master oscillator power amplifier structure. An laser diode arrays (LDA) side-pumped Nd:YAG acousto-optical (A-O) Q-switched laser serves as the master oscillator. Under pulsed pumping, pulse trains with 2-25 pulses are obtained when the repetition rate changes from 10 kHz to 100 kHz. The maximum pulse burst energy of 31.2 mJ is achieved in the A-O Q-switched pulse burst laser oscillator at 10 kHz. Two LDA side pumped Nd:YAG modules are employed in the amplification stage. After the amplification, the pulse burst energy at 10 kHz reaches ~170 mJ with a single pulse energy of 85.2 mJ and a pulse width of 14.5 ns, generating a peak power of 6.1 MW. At 100 kHz, the total burst energy reaches 220 mJ with a single pulse energy of 8.8 mJ in the pulse burst laser system.

  15. Sandia`s network for supercomputing `95: Validating the progress of Asynchronous Transfer Mode (ATM) switching

    SciTech Connect

    Pratt, T.J.; Vahle, O.; Gossage, S.A.

    1996-04-01

    The Advanced Networking Integration Department at Sandia National Laboratories has used the annual Supercomputing conference sponsored by the IEEE and ACM for the past three years as a forum to demonstrate and focus communication and networking developments. For Supercomputing `95, Sandia elected: to demonstrate the functionality and capability of an AT&T Globeview 20Gbps Asynchronous Transfer Mode (ATM) switch, which represents the core of Sandia`s corporate network, to build and utilize a three node 622 megabit per second Paragon network, and to extend the DOD`s ACTS ATM Internet from Sandia, New Mexico to the conference`s show floor in San Diego, California, for video demonstrations. This paper documents those accomplishments, discusses the details of their implementation, and describes how these demonstrations supports Sandia`s overall strategies in ATM networking.

  16. Mode-locked and Q-switched fiber lasers with graphene oxide based saturable absorber

    NASA Astrophysics Data System (ADS)

    Cheng, Zhaochen; Xu, Jia; Liu, Jiang; Ren, Jun; Wang, Pu

    2015-05-01

    We review our work on a femtosecond erbium-doped all-fiber laser mode-locked with graphene oxide saturable absorber, which can be conveniently obtained from natural graphite by simple oxidation and ultra-sonication process. The laser directly generated 200 fs pulses at a repetition rate of 22.9 MHz. The stable passively Q-switched operation by graphene oxide saturable absorber in the 1 μm ytterbium-, 1.5 μm erbium-, and 2 μm thulium-doped fiber lasers will be demonstrated as well. These results are comparable with those of graphene saturable absorbers and the superiority of easy fabrication and hydrophilic property of graphene oxide will facilitate its potential applications for ultrafast photonics.

  17. Transverse field-induced nucleation pad switching modes during domain wall injection

    SciTech Connect

    Bryan, M. T.; Fry, P. W.; Schrefl, T.; Gibbs, M. R. J.; Allwood, D. A.; Im, M.-Y.; Fischer, P.

    2010-03-12

    We have used magnetic transmission X-ray microscopy (M-TXM) to image in-field magnetization configurations of patterned Ni{sub 80}Fe{sub 20} domain wall 'injection pads' and attached planar nanowires. Comparison with micromagnetic simulations suggests that the evolution of magnetic domains in rectangular injection pads depends on the relative orientation of closure domains in the remanent state. The magnetization reversal pathway is also altered by the inclusion of transverse magnetic fields. These different modes explain previous results of domain wall injection into nanowires. Even more striking was the observation of domain walls injecting halfway across the width of wider (>400 nm wide) wires but over wire lengths of several micrometers. These extended Neel walls can interact with adjacent nanowires and cause a switching in the side of the wire undergoing reversal as the domain wall continues to expand.

  18. Automatic mode switching of implantable pacemakers: I. Principles of instrumentation, clinical, and hemodynamic considerations.

    PubMed

    Lau, Chu-Pak; Leung, Sum-Kin; Tse, Hung-Fat; Barold, S Serge

    2002-06-01

    Automatic mode switching (AMS) is now a programmable function in most contemporary dual chamber pacemakers. Atrial tachyarrhythmias are detected when the sensed atrial rate exceeds a "rate-cutoff," "running average," "sensor-based physiological" rate, or using "complex" detection algorithms. AMS algorithms differ in their atrial tachyarrhythmia detection method, sensitivity, and specificity and, thus, respond differently to atrial tachyarrhythmia in terms of speed to the AMS onset, rate stability of the response, and speed to resynchronize to sinus rhythm. AMS is hemodynamically beneficial, and most patients with atrial tachyarrhythmias are symptomatically better with an AMS algorithm in their pacemakers. New diagnostic capabilities of pacemaker especially stored electrograms not only allow programming of the AMS function, but enable quantification of atrial fibrillation burden that facilitate clinical management of patients with implantable devices who have concomitant atrial tachyarrhythmia.

  19. Depletion-Mode GaN HEMT Q-Spoil Switches for MRI Coils.

    PubMed

    Lu, Jonathan Y; Grafendorfer, Thomas; Zhang, Tao; Vasanawala, Shreyas; Robb, Fraser; Pauly, John M; Scott, Greig C

    2016-12-01

    Q-spoiling is the process of decoupling an MRI receive coil to protect the equipment and patient. Conventionally, Q-spoiling is performed using a PIN diode switch that draws significant current. In this work, a Q-spoiling technique using a depletion-mode Gallium Nitride HEMT device was developed for coil detuning at both 1.5 T and 3 T MRI. The circuits with conventional PIN diode Q-spoiling and the GaN HEMT device were implemented on surface coils. SNR was measured and compared for all surfaces coils. At both 1.5 T and 3 T, comparable SNR was achieved for all coils with the proposed technique and conventional Q-spoiling. The GaN HEMT device has significantly reduced the required power for Q-spoiling. The GaN HEMT device also provides useful safety features by detuning the coil when unpowered.

  20. All-optical scanhead for ultrasound and photoacoustic imaging—Imaging mode switching by dichroic filtering☆

    PubMed Central

    Hsieh, Bao-Yu; Chen, Sung-Liang; Ling, Tao; Guo, L. Jay; Li, Pai-Chi

    2014-01-01

    Ultrasound (US) and photoacoustic (PA) multimodality imaging has the advantage of combining good acoustic resolution with high optical contrast. The use of an all-optical scanhead for both imaging modalities can simplify integration of the two systems and miniaturize the imaging scanhead. Herein we propose and demonstrate an all-optical US/PA scanhead using a thin plate for optoacoustic generation in US imaging, a polymer microring resonator for acoustic detection, and a dichroic filter to switch between the two imaging modes by changing the laser wavelength. A synthetic-aperture focusing technique is used to improve the resolution and contrast. Phantom images demonstrate the feasibility of this design, and show that axial and lateral resolutions of 125 μm and 2.52°, respectively, are possible. PMID:25302154

  1. Pigeon interaction mode switch-based UAV distributed flocking control under obstacle environments.

    PubMed

    Qiu, Huaxin; Duan, Haibin

    2017-07-28

    Unmanned aerial vehicle (UAV) flocking control is a serious and challenging problem due to local interactions and changing environments. In this paper, a pigeon flocking model and a pigeon coordinated obstacle-avoiding model are proposed based on a behavior that pigeon flocks will switch between hierarchical and egalitarian interaction mode at different flight phases. Owning to the similarity between bird flocks and UAV swarms in essence, a distributed flocking control algorithm based on the proposed pigeon flocking and coordinated obstacle-avoiding models is designed to coordinate a heterogeneous UAV swarm to fly though obstacle environments with few informed individuals. The comparative simulation results are elaborated to show the feasibility, validity and superiority of our proposed algorithm. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  2. Methods for testing automatic mode switching in patients implanted with DDD(R) pacemakers.

    PubMed

    Lau, Chu-Pak; Mascia, Franco; Corbucci, Giorgio; Padeletti, Luigi

    2004-01-01

    The assessment of automatic mode switching (AMS) algorithms is impossible in vivo, due to a low chance of seeing the patient at the onset of a spontaneous episode of atrial fibrillation (AF). As the induction of AF to test AMS has clinical concerns, three alternative and non-invasive techniques may be proposed for this purpose: myopotentials, chest wall stimulation, and an external supraventricular arrhythmia simulator. The first method is simple and does not require additional equipment, even though in some patients adequate signals cannot be generated with a soft effort such as handgrip or hand compression. The main advantage of the chest wall stimulation method is the possibility that it be performed in every implanting center, since it is based on the use of standard devices for cardiac stimulation. The method based on the external supraventricular arrhythmia simulator allows the most detailed of the ECG traces, but it needs a dedicated electronic device.

  3. Importance of ventricular rate after mode switching during low intensity exercise as assessed by clinical symptoms and ventilatory gas exchange.

    PubMed

    Brunner-La Rocca, H P; Rickli, H; Weilenmann, D; Duru, F; Candinas, R

    2000-01-01

    Automatic mode switching from DDD(R) to DDI(R) or VVI(R) pacing modes has improved dual chamber pacing in patients at high risk for supraventricular tachyarrhythmias. However, little is known about the effect of ventricular pacing rate adaptation after mode switching. We conducted a single-blinded, crossover study in 15 patients (58 +/- 21 years) with a DDD pacemaker who had AV block and normal sinus node function to investigate the influence of pacing rate adaptation to intrinsic heart rate during low intensity exercise. Patients performed two tests (A/B) of low intensity treadmill exercise (0.5 W/kg) in randomized order. They initially walked for 6 minutes while paced in DDD mode. The pacing mode was then switched to VVI with a pacing rate of either 70 beats/min (test A) or matched to the intrinsic heart rate (95 +/- 11 beats/min test B). Respiratory gas exchange variables were determined and patients classified the effort before and after mode switching on a Borg scale from 6 to 20. Percentage changes of respiratory gas exchange measurements were significantly larger (O2 consumption: -8.2 +/- 5.0% vs. -0.6 +/- 7.2%; ventilatory equivalent of CO2 exhalation: 5.3 +/- 4.9% vs. 1.5 +/- 4.3%; respiratory exchange ratio: 7.0 +/- 2.2% vs. 3.5 +/- 3.0%; end-tidal CO2: -5.7 +/- 2.9% vs. -1.8 +/- 2.7%; all P < 0.01) and the increase in subjective assessment of the effort tended to be higher (mean increase on Borg scale: 1.6 +/- 1.9 vs. 1.1 +/- 1.8, P = 0.07) after heart rate unadjusted than after adjusted mode switching. Mode switching from DDD to VVI pacing is better tolerated and gas exchange measurements are less influenced if ventricular pacing rate is adjusted to the level of physical activity. Thus, pacing rate adjustment should be considered as part of automatic mode switch algorithms.

  4. Observer-based robust finite time H∞ sliding mode control for Markovian switching systems with mode-dependent time-varying delay and incomplete transition rate.

    PubMed

    Gao, Lijun; Jiang, Xiaoxiao; Wang, Dandan

    2016-03-01

    This paper investigates the problem of robust finite time H∞ sliding mode control for a class of Markovian switching systems. The system is subjected to the mode-dependent time-varying delay, partly unknown transition rate and unmeasurable state. The main difficulty is that, a sliding mode surface cannot be designed based on the unknown transition rate and unmeasurable state directly. To overcome this obstacle, the set of modes is firstly divided into two subsets standing for known transition rate subset and unknown one, based on which a state observer is established. A component robust finite-time sliding mode controller is also designed to cope with the effect of partially unknown transition rate. It is illustrated that the reachability, finite-time stability, finite-time boundedness, finite-time H∞ state feedback stabilization of sliding mode dynamics can be ensured despite the unknown transition rate. Finally, the simulation results verify the effectiveness of robust finite time control problem.

  5. Investigation of switching mechanism in HfOx-ReRAM under low power and conventional operation modes

    PubMed Central

    Feng, Wei; Shima, Hisashi; Ohmori, Kenji; Akinaga, Hiroyuki

    2016-01-01

    Low-power resistive random access memory (LP-ReRAM) devices have attracted increasing attention owing to their advantages of low operation power. In this study, a vertical-type LP-ReRAM consisting of TiN/Ti/HfO2/TiN structure was fabricated. The switching mechanism for LP-ReRAM was elucidated as the conductive filament mechanism for conventional mode, and an interface-type switching mechanism for low power mode was proposed. The analysis of low frequency noise shows that power spectral density (PSD) is approximately proportional to 1/f for conventional operation mode. Nevertheless, for low power mode, the PSD of low resistance state (LRS) is proportional to 1/f, while that of high resistance state (HRS) is clear proportional to 1/f2. The envelope of multiple Lorentzian spectra of 1/f2 characteristics due to different traps reveals the characteristics of 1/f. For HRS of low power mode, a limited number of traps results in a characteristic of 1/f2. During the set process, the number of oxygen vacancies increases for LRS. Therefore, the PSD value is proportional to 1/f. Owing to the increase in the number of traps when the operation mode changes to conventional mode, the PSD value is proportional to 1/f. To the best of our knowledge, this is the first study that reveals the different noise characteristics in the low power operation mode from that in the conventional operation mode. PMID:28000741

  6. Investigation of switching mechanism in HfOx-ReRAM under low power and conventional operation modes

    NASA Astrophysics Data System (ADS)

    Feng, Wei; Shima, Hisashi; Ohmori, Kenji; Akinaga, Hiroyuki

    2016-12-01

    Low-power resistive random access memory (LP-ReRAM) devices have attracted increasing attention owing to their advantages of low operation power. In this study, a vertical-type LP-ReRAM consisting of TiN/Ti/HfO2/TiN structure was fabricated. The switching mechanism for LP-ReRAM was elucidated as the conductive filament mechanism for conventional mode, and an interface-type switching mechanism for low power mode was proposed. The analysis of low frequency noise shows that power spectral density (PSD) is approximately proportional to 1/f for conventional operation mode. Nevertheless, for low power mode, the PSD of low resistance state (LRS) is proportional to 1/f, while that of high resistance state (HRS) is clear proportional to 1/f2. The envelope of multiple Lorentzian spectra of 1/f2 characteristics due to different traps reveals the characteristics of 1/f. For HRS of low power mode, a limited number of traps results in a characteristic of 1/f2. During the set process, the number of oxygen vacancies increases for LRS. Therefore, the PSD value is proportional to 1/f. Owing to the increase in the number of traps when the operation mode changes to conventional mode, the PSD value is proportional to 1/f. To the best of our knowledge, this is the first study that reveals the different noise characteristics in the low power operation mode from that in the conventional operation mode.

  7. Investigation of switching mechanism in HfOx-ReRAM under low power and conventional operation modes.

    PubMed

    Feng, Wei; Shima, Hisashi; Ohmori, Kenji; Akinaga, Hiroyuki

    2016-12-21

    Low-power resistive random access memory (LP-ReRAM) devices have attracted increasing attention owing to their advantages of low operation power. In this study, a vertical-type LP-ReRAM consisting of TiN/Ti/HfO2/TiN structure was fabricated. The switching mechanism for LP-ReRAM was elucidated as the conductive filament mechanism for conventional mode, and an interface-type switching mechanism for low power mode was proposed. The analysis of low frequency noise shows that power spectral density (PSD) is approximately proportional to 1/f for conventional operation mode. Nevertheless, for low power mode, the PSD of low resistance state (LRS) is proportional to 1/f, while that of high resistance state (HRS) is clear proportional to 1/f(2). The envelope of multiple Lorentzian spectra of 1/f(2) characteristics due to different traps reveals the characteristics of 1/f. For HRS of low power mode, a limited number of traps results in a characteristic of 1/f(2). During the set process, the number of oxygen vacancies increases for LRS. Therefore, the PSD value is proportional to 1/f. Owing to the increase in the number of traps when the operation mode changes to conventional mode, the PSD value is proportional to 1/f. To the best of our knowledge, this is the first study that reveals the different noise characteristics in the low power operation mode from that in the conventional operation mode.

  8. Shotgun lipidomics on a LTQ Orbitrap mass spectrometer by successive switching between acquisition polarity modes.

    PubMed

    Schuhmann, Kai; Almeida, Reinaldo; Baumert, Mark; Herzog, Ronny; Bornstein, Stefan R; Shevchenko, Andrej

    2012-01-01

    Top-down shotgun lipidomics relies on direct infusion of total lipid extracts into a high-resolution tandem mass spectrometer and implies that individual lipids are recognized by their accurately determined m/z. Lipid ionization efficiency and detection specificity strongly depend on the acquisition polarity, and therefore it is beneficial to analyze lipid mixtures in both positive and negative modes. Hybrid LTQ Orbitrap mass spectrometers are widely applied in top-down lipidomics; however, rapid polarity switching was previously unfeasible because of the severe and immediate degradation of mass accuracy. Here, we report on a method to rapidly acquire high-resolution spectra in both polarity modes with sub-ppm mass accuracy and demonstrate that it not only simplifies and accelerates shotgun lipidomics analyses but also improves the lipidome coverage because more lipid classes and more individual species within each class are recognized. In this way, shotgun analysis of total lipid extracts of human blood plasma enabled to quantify 222 species from 15 major lipid classes within 7 min acquisition cycle. Copyright © 2012 John Wiley & Sons, Ltd.

  9. Tunable graphene Q-switched erbium-doped fiber laser with suppressed self-mode locking effect.

    PubMed

    Zhou, Da-Peng; Wei, Li; Liu, Wing-Ki

    2012-05-10

    Self-mode locking effect in a wideband tunable graphene-based passively Q-switched erbium-doped fiber laser has been observed experimentally. Q-switching is achieved by using graphene as a saturable absorber, while a tunable bandpass filter with a narrow bandwidth is used to obtain wideband tunability. We propose to suppress the modulation on each pulse from self-mode locking by introducing three subring resonators constructed with three 3 dB couplers into the laser ring cavity. Moreover, the laser output characteristics with respect to pump power are studied in detail. A stable Q-switched erbium-doped fiber laser with a tunable range from 1522 nm to 1568 nm is demonstrated experimentally.

  10. Research on power equalization using a low-loss DC-DC chopper for lithium-ion batteries in electric vehicle

    NASA Astrophysics Data System (ADS)

    Wei, Y. W.; Liu, G. T.; Xiong, S. N.; Cheng, J. Z.; Huang, Y. H.

    2017-01-01

    In the near future, electric vehicle is entirely possible to replace traditional cars due to its zero pollution, small power consumption and low noise. Lithium-ion battery, which owns lots of advantages such as lighter and larger capacity and longer life, has been widely equipped in different electric cars all over the world. One disadvantage of this energy storage device is state of charge (SOC) difference among these cells in each series branch. If equalization circuit is not allocated for series-connected batteries, its safety and lifetime are declined due to over-charge or over-discharge happened, unavoidably. In this paper, a novel modularized equalization circuit, based on DC-DC chopper, is proposed to supply zero loss in theory. The proposed circuit works as an equalizer when Lithium-ion battery pack is charging or discharging or standing idle. Theoretical analysis and control method have been finished, respectively. Simulation and small scale experiments are applied to verify its real effect.

  11. Synchronously pumped mode-locked dye laser pumped by a frequency-doubled mode-locked and /ital Q/-switched diode laser pumped Nd:YAG laser

    SciTech Connect

    Maker, G. T.; Ferguson, A. I.

    1989-08-07

    We have developed a powerful and efficient mode-locked and /ital Q/-switched diode laser pumped Nd:YAG laser. Mode locking has been accomplished using intracavity frequency modulation (FM) to produce continuous-wave mode-locked pulses of 12 ps duration. Acousto-optic pre-lase /ital Q/ switching has produced a train of pulses of about 25 ps average duration at a repetition rate of 360 MHz in an envelope of 75 ns duration. When pumped with a 500 mW diode laser array, the energy in the /ital Q/-switched envelope was 15 /mu/J giving a peak power in the largest pulse of 19 kW. The laser has been frequency doubled in a crystal of potassium titanyl phosphate (KTP) with an efficiency of 36%. The doubled radiation at 532 nm has been used to synchronously pump a mode-locked rhodamine 6G dye laser to produce a train of tunable pulses. The pulse duration of the dye laser was 3.2 ps and the peak power of the largest pulse in the train was 10 kW.

  12. Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

    NASA Astrophysics Data System (ADS)

    Molli, Giancarlo; Menegon, Luca; Malasoma, Alessandro

    2017-04-01

    The switching in deformation mode (from distributed to localized) and mechanism (viscous versus frictional) represent a relevant issue in the frame of processes of crustal deformation in turn connected with the concept of the brittle-"ductile" transition and seismogenesis. On the other hand the role of brittle precursors in nucleating crystal-plastic shear zones has received more and more consideration being now recognized as having a fundamental role in the localization of deformation and shear zone development, thus representing a case in which switching deformation mode and mechanisms interact and relate to each other. This contribution analyses an example of a crystal plastic shear zone localized by brittle precursor formed within a host granitic-mylonite during deformation in subduction-related environment. The studied sample come from the external Corsican continental crust units involved in alpine age subduction and characterized by a low grade blueschist facies peak assemblages. The blueschist facies host rock is cut by a thin (< 1 cm thick) brittle-viscous shear zone that preserves domains with a cataclastic microstructure overprinted by mylonitic deformation. Blue amphibole is stable in the shear zone foliation, which therefore formed under HP/LT metamorphic conditions in a subduction environment. Quartz microstructure in the damage zone flanking the brittle-viscous shear zone shows evidence of both microcracking and dislocation glide, with limited recrystallization localized in intracrystalline bands. In the mylonite portion of the shear zone, quartz forms polycrystalline ribbons of dynamically recrystallized grains with a crossed-girdle c-axis CPO. Extrapolation of laboratory-derived flow laws indicates strain rate of ca. 3.5 * 10-12 s-1 during viscous flow in the shear zone. The studied structures, possibly formed by transient instability related to episodic stress/strain rate variations, may be considered as a small scale example of fault behaviour

  13. Power Quality Improvement in Bridgeless Ac-Dc Converter Based Multi-output Switched Mode Power Supply

    NASA Astrophysics Data System (ADS)

    Singh, Shihka; Singh, Bhim; Bhuvaneswari, G.; Bist, Vashist

    2014-12-01

    Computer power supplies are required to have multiple isolated regulated dc voltages with low ripple content and high input power factor at the utility interface. A dc-dc converter is used for obtaining these isolated multi-output dc voltages with excellent regulation. In this paper, a non-isolated ac-dc converter is proposed as the first stage converter to obtain a regulated dc output rather than using a simple uncontrolled diode bridge rectifier at the front end. A dc-dc converter is used at the second stage that has a high frequency transformer with multiple secondary windings to obtain different dc voltage levels at the output. The proposed bridgeless converter based power supply is designed using fundamental design equations, and different component values are calculated. Extensive simulations are carried out to demonstrate the improved performance of the proposed bridgeless converter based multi-output computer power supply at varying source voltages and load conditions. Experimental validation of the power supply is carried on a developed hardware prototype, and the test results are compared with the simulated performance for design verification.

  14. 40 Gb/s 2R Burst Mode Receiver with a single integrated SOA-MZI switch.

    PubMed

    Kanellos, G T; Pleros, N; Petrantonakis, D; Zakynthinos, P; Avramopoulos, H; Maxwell, G; Poustie, A

    2007-04-16

    We demonstrate a novel scheme for 2R burst mode reception capable of operating error-free with 40 Gb/s variable length, asynchronous optical data packets that exhibit up to 9 dB packet-to-packet power variation. It consists of a single, hybrid integrated, SOA-based Mach-Zehnder Interferometer (SOA-MZI) with unequal splitting ratio couplers, configured to operate as a self-switch. We analyze theoretically the power equalization properties of unequal splitting ratio SOA-MZI switches and show good agreement between theory and experiment.

  15. Challenges and implementation aspects of switched-mode power supplies with digital control for automotive applications

    NASA Astrophysics Data System (ADS)

    Quenzer-Hohmuth, Samuel; Rosahl, Thoralf; Ritzmann, Steffen; Wicht, Bernhard

    2016-09-01

    Switched-mode power supplies (SMPS) convert an input DC-voltage into a higher or lower output voltage. In automotive, analog control is mostly used in order to keep the required output voltages constant and resistant to disturbances. The design of robust analog control for SMPS faces parameter variations of integrated and external passive components. Using digital control, parameter variations can be eliminated and the required area for the integrated circuit can be reduced at the same time. Digital control design bears challenges like the prevention of limit cycle oscillations and controller-wind-up. This paper reviews how to prevent these effects. Digital control loops introduce new sources for dead times in the control loop, for example the latency of the analog-to-digital-converter (ADC). Dead times have negative influence on the stability of the control loop, because they lead to phase delays. Consequently, low latency is one of the key requirements for analog-to-digital-converters in digitally controlled SMPS. Exploiting the example of a 500 kHz-buck converter with a crossover frequency of 70 kHz, this paper shows that the 5 µs-latency of a ΔΣ-analog-to-digital-converter leads to a reduction in phase margin of 126°. The latency is less critical for boost converters because of their inherent lower crossover frequencies. Finally, the paper shows a comparison between analog and digital control of SMPS with regard to chip area and test costs.

  16. Dual-mode ion switching conducting polymer films as high energy supercapacitor materials

    SciTech Connect

    Naoi, Katsuhiko; Oura, Yasushi

    1995-12-31

    The electropolymerized polypyrrole films formed from micellar solution of anionic surfactants, viz., Dodecylbenzene sulfonate (DBS), showed potential-dependent anion and cation ion switching behavior and the peculiar columnar structure. The formation process and the redox of the polypyrrole was studied with the in situ atomic force microscopy (AFM) and electrochemical quartz crystal microbalance (EQCM) methods. In-situ AFM observation clearly indicated that such a columnar structure started to form around critical charge densities of 60--100 mC cm{sup {minus}2}. The cyclic voltammogram for the PPy doped with DBS{sup {minus}} film showed two redox couples, each of which corresponds to a cation and an anion exchange process. Thus, the film behaves as a dual-mode ion doping/undoping exchanger. As the PPy film was prepared in higher concentration of the surfactant dopant, where the micelles are formed in solution, the resulting film showed a considerably higher (ca. three orders of magnitude) diffusion coefficient compared to ordinary PPy films so far reported. Such an enhanced diffusivity of ions could be attributed to a peculiar structure of the polymer formed. The feasibility of such polypyrrole in use of supercapacitor material was discussed.

  17. Determination of appropriate DC voltage for switched mode power supply (SMPS) loads

    NASA Astrophysics Data System (ADS)

    Setiawan, Eko Adhi; Setiawan, Aiman; Purnomo, Andri; Djamal, Muchlishah Hadi

    2017-03-01

    Nowadays, most of modern and efficient household electronic devices operated based on Switched Mode Power Supply (SMPS) technology which convert AC voltage from the grid to DC voltage. Based on theory and experiment, SMPS loads could be supplied by DC voltage. However, the DC voltage rating to energize electronic home appliances is not standardized yet. This paper proposed certain method to determine appropriate DC voltage, and investigated comparison of SMPS power consumption which is supplied from AC and DC voltage. To determine the appropriate DC voltage, lux value of several lamps which have same specification energized by using AC voltage and the results is using as reference. Then, the lamps were supplied by various DC voltage to obtain the trends of the lux value to the applied DC voltage. After that, by using the trends and the reference lux value, the appropriate DC voltage can be determined. Furthermore, the power consumption on home appliances such as mobile phone, laptop and personal computer by using AC voltage and the appropriate DC voltage were conducted. The results show that the total power consumption of AC system is higher than DC system. The total power (apparent power) consumed by the lamp, mobile phone and personal computer which operated in 220 VAC were 6.93 VA, 34.31 VA and 105.85 VA respectively. On the other hand, under 277 VDC the load consumption were 5.83 W, 19.11 W and 74.46 W respectively.

  18. Nonpolar resistive memory switching with all four possible resistive switching modes in amorphous LaHoO{sub 3} thin films

    SciTech Connect

    Sharma, Yogesh; Pavunny, Shojan P.; Katiyar, Ram S.; Fachini, Esteban; Scott, James F.

    2015-09-07

    We studied the resistive memory switching in pulsed laser deposited amorphous LaHoO{sub 3} (a-LHO) thin films for non-volatile resistive random access memory applications. Nonpolar resistive switching (RS) was achieved in Pt/a-LHO/Pt memory cells with all four possible RS modes (i.e., positive unipolar, positive bipolar, negative unipolar, and negative bipolar) having high R{sub ON}/R{sub OFF} ratios (in the range of ∼10{sup 4}–10{sup 5}) and non-overlapping switching voltages (set voltage, V{sub ON} ∼ ±3.6–4.2 V and reset voltage, V{sub OFF} ∼ ±1.3–1.6 V) with a small variation of about ±5–8%. Temperature dependent current-voltage (I–V) characteristics indicated the metallic conduction in low resistance states (LRS). We believe that the formation (set) and rupture (reset) of mixed conducting filaments formed out of oxygen vacancies and metallic Ho atoms could be responsible for the change in the resistance states of the memory cell. Detailed analysis of I–V characteristics further corroborated the formation of conductive nanofilaments based on metal-like (Ohmic) conduction in LRS. Simmons-Schottky emission was found to be the dominant charge transport mechanism in the high resistance state.

  19. A simple and tunable switch between slow- and fast-light in two signal modes with an optomechanical system

    NASA Astrophysics Data System (ADS)

    Ma, Peng-Cheng; Yan, Lei-Lei; Chen, Gui-Bin; Li, Xiao-Wei; Zhan, You-Bang

    2016-12-01

    The control of slow and fast light propagation is a challenging task. Here, we theoretically study the dynamics of a driven optomechanical cavity coupled to a charged nanomechanical resonator (NR) via Coulomb interaction. We find that the tunable switch between slow- and fast-light for two signal modes can be observed from the output field by adjusting the laser-cavity detuning in this system. Moreover, the frequencies of two signal light can be tuned by Coulomb coupling strength. In comparison with previous schemes, the clear advantage of our scheme is that we can simply switch from fast- to slow-light in two signal modes by only adjusting the laser-cavity deturning from Δ ={ω1} to Δ =-{ω1} . The proposal may have potential application in optical router and quantum optomechanical memory.

  20. An actively Q-switched single-longitudinal-mode fiber laser with an optically pumped saturable absorber

    NASA Astrophysics Data System (ADS)

    Yun, Hyo-Geun; Lee, Seoung Hun; Lee, Min Hee; Kim, Kyong Hon

    2013-09-01

    We have demonstrated an actively Q-switched single-longitudinal-mode (SLM) erbium-doped fiber (EDF) ring laser by using an EDF saturable absorber modulated under an external laser pulse injection. A laser output of 1531.9 nm wavelength from a distributed-feedback laser diode was amplified with an EDF amplifier and modulated with an external electro-optical modulator, and the modulated signals were used as control pulses to saturate the EDF saturable absorber for the actively Q-switched ring-type fiber laser operation. Actively Q-switched 1542 nm wavelength laser pulses of 4.5 nJ pulse energy and of 4.0μs pulse width were achieved at a repetition rate of 100 Hz. When the Q-switched laser pulse energy was reduced to about 0.54 nJ by decreasing the gain-pump power used for exciting the ring cavity and the control-pulse beam power used for bleaching out the saturable absorber, the SLM laser pulses were achieved. Further improvement of the Q-switched SLM laser pulse output can be achieved simply by using an external laser amplifier and by shortening the cavity length with short pigtailed-fiber laser components, and thus the SLM laser pulses can be useful for various applications.

  1. Mode locking and Q switching of a diode laser pumped neodymium-doped yttrium lithium fluoride laser

    SciTech Connect

    Maker, G.T.; Ferguson, A.I.

    1989-01-30

    We have developed a mode-locked, diode pumped, neodymium-doped yttrium lithium fluoride (Nd:YLF) laser operating at 1.053 ..mu..m. The laser produces pulses of 18 ps duration at an average power level of 12 mW. When Q switched the duration of the pulse train was 140 ns, giving rise to peak powers of 15 kW.

  2. Intrinsic neuronal properties switch the mode of information transmission in networks.

    PubMed

    Gjorgjieva, Julijana; Mease, Rebecca A; Moody, William J; Fairhall, Adrienne L

    2014-12-01

    represent and propagate information, and suggests a role for background synaptic noise in switching the mode of information transmission.

  3. Passively Q-switched and mode-locked erbium doped fiber laser based on N-doped graphene saturable absorber

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Aidit, S. N.; Ooi, S. I.; Rezayi, M.; Tiu, Z. C.

    2017-10-01

    A passively Q-switched and mode-locked erbium-doped fiber laser based on a nitrogen-doped graphene saturable absorber is demonstrated. The N-doped graphene based saturable absorber has a modulation depth of 37.88% and a saturation intensity of 0.016 73 MW cm‑2. By integrating the N-doped graphene saturable absorber into the laser cavity, a stable Q-switched operation with a centre wavelength of 1561.1 nm is obtained with a pulse energy of up to 29.0 nJ. As the pump power increases, the Q-switching operation transits into a mode-locking operation. The mode-locking operation is achieved with a centre wavelength of 1560 nm, a pulse width of 0.98 ps, a repetition rate of 28.5 MHz and a signal to noise ratio of up to 40 dB in the RF spectrum.

  4. Multilayer graphene for Q-switched mode-locking operation in an erbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Wang, Zhiteng; Zhu, Shou-En; Chen, Yu; Wu, Man; Zhao, Chujun; Zhang, Han; Janssen, G. C. A. M.; Wen, Shuangchun

    2013-07-01

    We report the laser operation of Q-switched mode-locking (QML) in an erbium-doped fiber laser by using a multilayer graphene saturable absorber (SA), which consists of 22-layer of graphene fabricated by the chemical vapor deposition method. Based on our balanced twin detector measurement, the graphene sample is confirmed to show a saturable intensity of 3.375 MW/cm2 and an absolute modulation depth of 40.27%. It is demonstrated that this graphene SA can readily produce high quality QML pulses. At the pump power of 391.9 mW, the stable mode-locked pulse train with the Q-switched envelope repetition rate of 16.98 kHz and the envelope width of 13.84 μs are achieved. The maximal main pulse peak power can reach up to 35.89 W. This verifies that the multilayer graphene can be still applied as an effective saturable absorber for passively Q-switched mode-locked operation.

  5. The Finite Horizon Optimal Multi-Modes Switching Problem: The Viscosity Solution Approach

    SciTech Connect

    El Asri, Brahim Hamadene, Said

    2009-10-15

    In this paper we show existence and uniqueness of a solution for a system of m variational partial differential inequalities with inter-connected obstacles. This system is the deterministic version of the Verification Theorem of the Markovian optimal m-states switching problem. The switching cost functions are arbitrary. This problem is in relation with the valuation of firms in a financial market.

  6. 25-Gbit/s burst-mode optical receiver using high-speed avalanche photodiode for 100-Gbit/s optical packet switching.

    PubMed

    Nada, Masahiro; Nakamura, Makoto; Matsuzaki, Hideaki

    2014-01-13

    25-Gbit/s error-free operation of an optical receiver is successfully demonstrated against burst-mode optical input signals without preambles. The receiver, with a high-sensitivity avalanche photodiode and burst-mode transimpedance amplifier, exhibits sufficient receiver sensitivity and an extremely quick response suitable for burst-mode operation in 100-Gbit/s optical packet switching.

  7. Simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822-09

    NASA Astrophysics Data System (ADS)

    Hermsen, W.; Kuiper, L.; Hessels, J. W. T.; Mitra, D.; Rankin, J. M.; Stappers, B. W.; Wright, G. A. E.; Basu, R.; Szary, A.; van Leeuwen, J.

    2017-04-01

    We report on simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822-09 with ESA's XMM-Newton and the Westerbork Synthesis Radio Telescope, Giant Metrewave Radio Telescope and Lovell radio telescopes. PSR B1822-09 switches between a radio-bright and radio-quiet mode, and we discovered a relationship between the durations of its modes and a known underlying radio-modulation time-scale within the modes. We discovered X-ray (energies 0.2-1.4 keV) pulsations with a broad sinusoidal pulse, slightly lagging the radio main pulse in phase by 0.094 ± 0.017, with an energy-dependent pulsed fraction varying from ∼0.15 at 0.3 keV to ∼0.6 at 1 keV. No evidence is found for simultaneous X-ray and radio mode switching. The total X-ray spectrum consists of a cool component (T ∼0.96 × 106 K, hotspot radius R ∼2.0 km) and a hot component (T ∼2.2 × 106 K, R ∼100 m). The hot component can be ascribed to the pulsed emission and the cool component to the unpulsed emission. The high-energy characteristics of PSR B1822-09 resemble those of middle-aged pulsars such as PSR B0656+14, PSR B1055-52 and Geminga, including an indication for pulsed high-energy gamma-ray emission in Fermi Large Area Telescope data. Explanations for the high pulsed fraction seem to require different temperatures at the two poles of this orthogonal rotator, or magnetic anisotropic beaming effects in its strong magnetic field. In our X-ray skymap, we found a harder source at only 5.1 ± 0.5 arcsec from PSR B1822-09, which might be a pulsar wind nebula.

  8. A Deep Campaign to Characterize the Synchronous Radio/X-Ray Mode Switching of PSR B0943+10

    NASA Astrophysics Data System (ADS)

    Mereghetti, S.; Kuiper, L.; Tiengo, A.; Hessels, J.; Hermsen, W.; Stovall, K.; Possenti, A.; Rankin, J.; Esposito, P.; Turolla, R.; Mitra, D.; Wright, G.; Stappers, B.; Horneffer, A.; Oslowski, S.; Serylak, M.; Grießmeier, J.-M.

    2016-11-01

    Observations of PSR B0943+10 with XMM-Newton and the LOFAR, LWA, and Arecibo radio telescopes in 2014 November confirm the synchronous X-ray/radio switching between a radio-bright (B) mode and a radio-quiet (Q) mode, in which the X-ray flux is a factor ˜2.4 higher than in the B-mode. We discovered X-ray pulsations during the B-mode (0.5-2 keV pulsed fraction of (38 ± 5)%) and confirm their presence in the Q-mode, where the pulsed fraction increases with energy from ˜20% to ˜65% at 2 keV. We found marginal evidence for an increase in the X-ray pulsed fraction during the B-mode on a timescale of hours. The X-ray spectrum during the Q-mode requires a fit with either a power law plus blackbody or the sum of two blackbodies, while in the B-mode it is well fit by a single blackbody (a single power law is rejected). In the Q-mode, the pulsed emission has a blackbody spectrum with temperature ˜ 3.4× {10}6 K and the unpulsed emission is a power law with photon index ˜2.5, while during the B-mode both the pulsed and unpulsed emission can be fit by either a blackbody or a power law with similar values of temperature and index. A Chandra image does not show diffuse X-ray emission. These results support a scenario in which unpulsed non-thermal emission, likely magnetospheric, and pulsed thermal emission from a small polar cap (˜1500 m2) with a non-dipolar field (˜1014 G) are present during both modes and vary in a correlated way. This is broadly consistent with the partially screened gap model and does not necessarily imply global magnetospheric rearrangements to explain the mode switching.

  9. A Cr4+:YAG passively Q-switched Nd:YVO4 microchip laser for controllable high-order Hermite-Gaussian modes

    NASA Astrophysics Data System (ADS)

    Dong, Jun; He, Yu; Bai, Sheng-Chuang; Ueda, Ken-ichi; Kaminskii, Alexander A.

    2016-09-01

    A nanosecond, high peak power, passively Q-switched laser for controllable Hermite-Gaussian (HG) modes has been achieved by manipulating the saturated inversion population inside the gain medium. The stable HG modes are generated in a Cr4+:YAG passively Q-switched Nd:YVO4 microchip laser by applying a tilted pump beam. The asymmetrical saturated inversion population distribution inside the Nd:YVO4 crystal for desirable HG modes is manipulated by choosing the proper pump beam diameter and varying pump power. A HG9,8 mode passively Q-switched Nd:YVO4 microchip laser with average output power of 265 mW has been obtained. Laser pulses with a pulse width of 7.3 ns and peak power of over 1.7 kW working at 21 kHz have been generated in the passively Q-switched Nd:YVO4 microchip laser.

  10. Exciter switch

    NASA Technical Reports Server (NTRS)

    Mcpeak, W. L.

    1975-01-01

    A new exciter switch assembly has been installed at the three DSN 64-m deep space stations. This assembly provides for switching Block III and Block IV exciters to either the high-power or 20-kW transmitters in either dual-carrier or single-carrier mode. In the dual-carrier mode, it provides for balancing the two drive signals from a single control panel located in the transmitter local control and remote control consoles. In addition to the improved switching capabilities, extensive monitoring of both the exciter switch assembly and Transmitter Subsystem is provided by the exciter switch monitor and display assemblies.

  11. Survival and failure modes: platform-switching for internal and external hexagon cemented fixed dental prostheses.

    PubMed

    Anchieta, Rodolfo B; Machado, Lucas S; Hirata, Ronaldo; Coelho, Paulo G; Bonfante, Estevam A

    2016-10-01

    This study evaluated the probability of survival (reliability) of platform-switched fixed dental prostheses (FDPs) cemented on different implant-abutment connection designs. Eighty-four-three-unit FDPs (molar pontic) were cemented on abutments connected to two implants of external or internal hexagon connection. Four groups (n = 21 each) were established: external hexagon connection and regular platform (ERC); external hexagon connection and switched platform (ESC); internal hexagon and regular platform (IRC); and internal hexagon and switched platform (ISC). Prostheses were subjected to step-stress accelerated life testing in water. Weibull curves and probability of survival for a mission of 100,000 cycles at 400 N (two-sided 90% CI) were calculated. The beta values of 0.22, 0.48, 0.50, and 1.25 for groups ERC, ESC, IRC, and ISC, respectively, indicated a limited role of fatigue in damage accumulation, except for group ISC. Survival decreased for both platform-switched groups (ESC: 74%, and ISC: 59%) compared with the regular matching platform counterparts (ERC: 95%, and IRC: 98%). Characteristic strength was higher only for ERC compared with ESC, but not different between internal connections. Failures chiefly involved the abutment screw. Platform switching decreased the probability of survival of FDPs on both external and internal connections. The absence in loss of characteristic strength observed in internal hexagon connections favor their use compared with platform-switched external hexagon connections. © 2016 Eur J Oral Sci.

  12. Analysis of the Hysteresis Phenomenon in the Intrinsic Half-V-Shaped Switching Ferroelectric Liquid Crystal Mode

    NASA Astrophysics Data System (ADS)

    Asao, Yasufumi; Yoshinaga, Hideki; Isobe, Ryuichiro; Togano, Takeshi; Mori, Hideo

    2003-09-01

    The intrinsic half-V-shaped switching ferroelectric liquid crystal mode (iHV-FLC mode) is known to be able to easily yield excellent moving pictures without blurring, based on the nonholding display by simple AC driving in the ideal condition. However, we have sometimes observed the blurred moving pictures even in the iHV-FLC mode with very short response time. We have conducted the detailed measurement of the electrooptical response. The protracted hysteresis phenomenon could be observed in some cells. This phenomenon had a strong relationship with the internal ionic impurity density. The 1st frame hysteresis phenomenon could be observed even in the purest cells. It is considered to be caused by the c-director position at zero field and its driving scheme.

  13. On the functional significance of retrieval mode: Task switching disrupts the recollection of conceptual stimulus information from episodic memory.

    PubMed

    Küper, Kristina

    2017-10-03

    Episodic memory retrieval is assumed to be associated with the tonic cognitive state of retrieval mode. Despite extensive research into the neurophysiological correlates of retrieval mode, as of yet, relatively little is known about its functional significance. The present event-related potential (ERP) study was aimed at examining the impact of retrieval mode on the specificity of memory content retrieved in the course of familiarity and recollection processes. In two experiments, participants performed a recognition memory inclusion task in which they had to distinguish identically repeated and re-colored versions of study items from new items. In Experiment 1, participants had to alternate between the episodic memory task and a semantic task requiring a natural/artificial decision. In Experiment 2, the two tasks were instead performed in separate blocks. ERPs locked to the preparatory cues in the test phases indicated that participants did not establish retrieval mode on switch trials in Experiment 1. In the absence of retrieval mode, neither type of studied item elicited ERP correlates of familiarity-based retrieval (FN400). Recollection-related late positive complex (LPC) old/new effects emerged only for identically repeated but not for conceptually identical but perceptually changed versions of study items. With blocked retrieval in Experiment 2, both types of old items instead elicited equivalent FN400 and LPC old/new effects. The LPC data indicate that retrieval mode may play an important role in the successful recollection of conceptual stimulus information. The FN400 results additionally suggest that task switching may have a detrimental effect on familiarity-based memory retrieval. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Hippocampal pyramidal neurons switch from a multipolar migration mode to a novel "climbing" migration mode during development.

    PubMed

    Kitazawa, Ayako; Kubo, Ken-ichiro; Hayashi, Kanehiro; Matsunaga, Yuki; Ishii, Kazuhiro; Nakajima, Kazunori

    2014-01-22

    The hippocampus plays important roles in brain functions. Despite the importance of hippocampal functions, recent analyses of neuronal migration have mainly been performed on the cerebral neocortex, and the cellular mechanisms responsible for the formation of the hippocampus are not yet completely understood. Moreover, why a prolonged time is required for hippocampal neurons to complete their migration has been unexplainable for several decades. We analyzed the migratory profile of neurons in the developing mouse hippocampal CA1 region and found that the hippocampal pyramidal neurons generated near the ventricle became postmitotic multipolar cells and accumulated in the multipolar cell accumulation zone (MAZ) in the late stage of development. The hippocampal neurons passed through the pyramidal layer by a unique mode of migration. Their leading processes were highly branched and made contact with many radial fibers. Time-lapse imaging revealed that the migrating cells changed their scaffolds from the original radial fibers to other radial fibers, and as a result they proceed in a zigzag manner, with long intervals. The migrating cells in the hippocampus reminded us of "rock climbers" that instead of using their hands to pull up their bodies were using their leading processes to pull up their cell bodies. Because this mode of migration had never been described, we called it the "climbing" mode. The change from the "climbing" mode in the hippocampus to the "locomotion" mode in the neocortex may have contributed to the brain expansion during evolution.

  15. Effect of cavity length on low-energy single longitudinal mode pre-lase Q-switched laser

    NASA Astrophysics Data System (ADS)

    Qing-Song, Li; Yuan, Dong; Yu, Liu; Xi-He, Zhang; Yong-Ji, Yu; Guang-Yong, Jin

    2017-09-01

    In this paper, the effect of cavity length on a low-energy single longitudinal mode (SLM) pre-lase Q-switched laser is analyzed and demonstrated. Taking a Pr:YLF laser as an example, the basic output characteristics under pre-lase technology are shown. The SLM is degraded when the cavity length is as large as 25 mm. Further, for cavity lengths of 15 or 20 mm, SLM is achieved with different output characteristics. Compared with a long cavity (20 mm), the short-cavity case (15 mm) is indeed helpful for obtaining an SLM laser; however, the single-pulse energy, pulse width, and energy extraction efficiency are decreased by 4.7, 48, and 6.7%, respectively. The results of this analysis show that the cavity length influences the output characteristics and determines the realization of SLM in a pre-lase Q-switched laser. This is because the short cavity induces a relatively strong gain identification for the seed signal. Then, the time cost of the mode competition decreases and SLM can be achieved easily. However, a long cavity is conducive to mode competition, which generates superior output characteristics.

  16. WS₂ as a saturable absorber for ultrafast photonic applications of mode-locked and Q-switched lasers.

    PubMed

    Wu, Kan; Zhang, Xiaoyan; Wang, Jun; Li, Xing; Chen, Jianping

    2015-05-04

    Two-dimensional (2D) nanomaterials, especially the transition metal sulfide semiconductors, have drawn great interests due to their potential applications in viable photonic and optoelectronic devices. In this work, 2D tungsten disulfide (WS2) based saturable absorber (SA) for ultrafast photonic applications was demonstrated. WS2 nanosheets were prepared using liquid-phase exfoliation method and embedded in polyvinyl alcohol (PVA) thin film for the practical usage. Saturable absorption was discovered in the WS2-PVA SA at the telecommunication wavelength near 1550 nm. By incorporating WS2-PVA SA into a fiber laser cavity, both stable mode locking operation and Q-switching operation were achieved. In the mode locking operation, the laser obtained femtosecond output pulse width and high spectral purity in the radio frequency spectrum. In the Q-switching operation, the laser had tunable repetition rate and output pulse energy of a few tens of nano joule. Our findings suggest that few-layer WS2 nanosheets embedded in PVA thin film are promising nonlinear optical materials for ultrafast photonic applications as a mode locker or Q-switcher.

  17. Short-pulse controlled optical switch using external cavity based single mode Fabry-Pérot laser diode.

    PubMed

    Nakarmi, Bikash; Hoai, Tran Quoc; Won, Yong-Hyub; Zhang, Xuping

    2014-06-30

    We propose and demonstrate a novel scheme for short pulse controlled all-optical switch using external cavity based single mode Fabry- Pérot laser diode (SMFP-LD). The proposed scheme consists of control unit and switching unit as two essential blocks. The basic principle of the proposed scheme is the optical bistability property of SMFP-LD for the control unit and the suppression of the dominant beam of SMFP-LD with injection locking for the switching unit. We also present the analysis of hysteresis width and rising/falling time with change in wavelength detuning which helps to find the optimum wavelength detuning value and power of light beams at different stages of the proposed scheme that gives wide input dynamic power range, high ON/OFF contrast ratio, and low rising/falling time. Input data of 10 Gb/s Non Return to Zero (NRZ) signal is switched at output ports depending upon the control signal generated by the control unit, which comprises of optical SR latch. Output waveforms, clear eye diagrams with extinction ratio of about 11 dB, rising/falling time of about 30 ps and 40 ps, and bit error rate (BER) are measured to validate proposed scheme. No noise floor is observed at output ports up to BER of 10-(12) and the maximum power penalty recorded is about 1.7 dB at a BER of 10-(9) which shows good performance of the proposed short pulse controlled optical switch using SMFP-LDs.

  18. Q-switched and mode-locked Er{sup 3+}-doped fibre laser using a single-multi-single fibre filter and piezoelectric

    SciTech Connect

    Ji Wang; Yunjun Zhang; Aotuo Dong; Xiaoxin Xu; Youlun Ju; Baoquan Yao

    2014-04-28

    The active Q-switched and passive mode-locked Er{sup 3+}-doped all-fibre laser is presented. The fibre laser centre wavelength is located at 1563 nm and determined by the homemade singlemulti- single (SMS) in-line fibre filter. The laser spectrum width is nearly 0.1 nm. The active Q-switched mechanism relies on the polarisation state control using a piezoelectric to press a segment of passive fibre on the circular cavity. The nonlinear polarisation rotation technology is used to realise the passive self-started modelocked operation. In the passive mode-locked regimes, the output average power is 2.1 mW, repetition frequency is 11.96 MHz, and single pulse energy is 0.18 nJ. With the 100-Hz Q-switched regimes running, the output average power is 1.5 mW. The total Q-switched pulse width is 15 μs, and every Q-switched pulse is made up by several tens of mode-locked peak pulses. The calculated output pulse energy of the Q-switched fibre laser is about 15 μJ, and the energy of every mode-locked pulse is about 64–68 nJ during a Q-switched pulse taking into account the power fraction propagating between pulses. (lasers)

  19. Q-switched and mode-locked Er3+-doped fibre laser using a single-multi-single fibre filter and piezoelectric

    NASA Astrophysics Data System (ADS)

    Wang, Ji; Zhang, Yunjun; Dong, Aotuo; Xu, Xiaoxin; Ju, Youlun; Yao, Baoquan

    2014-04-01

    The active Q-switched and passive mode-locked Er3+-doped all-fibre laser is presented. The fibre laser centre wavelength is located at 1563 nm and determined by the homemade singlemulti- single (SMS) in-line fibre filter. The laser spectrum width is nearly 0.1 nm. The active Q-switched mechanism relies on the polarisation state control using a piezoelectric to press a segment of passive fibre on the circular cavity. The nonlinear polarisation rotation technology is used to realise the passive self-started modelocked operation. In the passive mode-locked regimes, the output average power is 2.1 mW, repetition frequency is 11.96 MHz, and single pulse energy is 0.18 nJ. With the 100-Hz Q-switched regimes running, the output average power is 1.5 mW. The total Q-switched pulse width is 15 μs, and every Q-switched pulse is made up by several tens of mode-locked peak pulses. The calculated output pulse energy of the Q-switched fibre laser is about 15 μJ, and the energy of every mode-locked pulse is about 64-68 nJ during a Q-switched pulse taking into account the power fraction propagating between pulses.

  20. Characteristics of polarization switching from the low to the high frequency mode in vertical-cavity surface-emitting lasers

    SciTech Connect

    Ackemann, T.; Sondermann, M.

    2001-06-04

    Polarization selection in small-area vertical-cavity surface-emitting lasers is studied experimentally in dependence of injection current and substrate temperature in the vicinity of the minimum threshold condition. Polarization switching from the low to the high frequency fundamental spatial mode is demonstrated. The effective birefringence displays a minimum in the transition region. The observation of dynamical transition states hints to the relevance of nonlinear effects. A comparison to the predictions of the San Miguel{endash}Feng{endash}Moloney model based on phase-amplitude coupling is given. {copyright} 2001 American Institute of Physics.

  1. Q-switched-like soliton bunches and noise-like pulses generation in a partially mode-locked fiber laser.

    PubMed

    Wang, Zhenhong; Wang, Zhi; Liu, Yan-Ge; Zhao, Wenjing; Zhang, Hao; Wang, Shangcheng; Yang, Guang; He, Ruijing

    2016-06-27

    We report an intermediate regime between c.w. emission and noise-like pulses (NLPs) regime in an Er-doped partially mode-locked fiber laser with nonlinear polarization rotation. In this regime, the soliton bunches stochastically turn up from a quasi-cw background in the Q-switched-like envelope. The soliton bunches normally last for tens or hundreds of intracavity round-trips. When the soliton bunches vanish, typical NLPs chains are generated sporadically at location where the soliton bunches collapses. These results would be helpful to understand the generation and property of the NLPs regime.

  2. How yawning switches the default-mode network to the attentional network by activating the cerebrospinal fluid flow.

    PubMed

    Walusinski, Olivier

    2014-03-01

    Yawning is a behavior to which little research has been devoted. However, its purpose has not yet been demonstrated and remains controversial. In this article, we propose a new theory involving the brain network that is functional during the resting state, that is, the default mode network. When this network is active, yawning manifests a process of switching to the attentional system through its capacity to increase circulation of cerebrospinal fluid (CSF), thereby increasing clearance of somnogenic factors (prostaglandin D(2), adenosine, and others) accumulating in the cerebrospinal fluid. Copyright © 2013 Wiley Periodicals, Inc.

  3. Simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822$-$09

    DOE PAGES

    Hermsen, W.; Kuiper, L.; Hessels, J. W. T.; ...

    2016-12-05

    Here, we report on simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822–09 with ESA's XMM–Newton and the Westerbork Synthesis Radio Telescope, Giant Metrewave Radio Telescope and Lovell radio telescopes. PSR B1822–09 switches between a radio-bright and radio-quiet mode, and we discovered a relationship between the durations of its modes and a known underlying radio-modulation time-scale within the modes. We discovered X-ray (energies 0.2–1.4 keV) pulsations with a broad sinusoidal pulse, slightly lagging the radio main pulse in phase by 0.094 ± 0.017, with an energy-dependent pulsed fraction varying from ~0.15 at 0.3 keV to ~0.6 at 1more » keV. No evidence is found for simultaneous X-ray and radio mode switching. The total X-ray spectrum consists of a cool component (T ~0.96 × 106 K, hotspot radius R ~2.0 km) and a hot component (T ~2.2 × 106 K, R ~100 m). The hot component can be ascribed to the pulsed emission and the cool component to the unpulsed emission. The high-energy characteristics of PSR B1822–09 resemble those of middle-aged pulsars such as PSR B0656+14, PSR B1055–52 and Geminga, including an indication for pulsed high-energy gamma-ray emission in Fermi Large Area Telescope data. Explanations for the high pulsed fraction seem to require different temperatures at the two poles of this orthogonal rotator, or magnetic anisotropic beaming effects in its strong magnetic field. In our X-ray skymap, we found a harder source at only 5.1 ± 0.5 arcsec from PSR B1822–09, which might be a pulsar wind nebula.« less

  4. Simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822$-$09

    SciTech Connect

    Hermsen, W.; Kuiper, L.; Hessels, J. W. T.; Mitra, D.; Rankin, J. M.; Stappers, B. W.; Wright, G. A. E.; Basu, R.; Szary, A.; van Leeuwen, J.

    2016-12-05

    Here, we report on simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822–09 with ESA's XMM–Newton and the Westerbork Synthesis Radio Telescope, Giant Metrewave Radio Telescope and Lovell radio telescopes. PSR B1822–09 switches between a radio-bright and radio-quiet mode, and we discovered a relationship between the durations of its modes and a known underlying radio-modulation time-scale within the modes. We discovered X-ray (energies 0.2–1.4 keV) pulsations with a broad sinusoidal pulse, slightly lagging the radio main pulse in phase by 0.094 ± 0.017, with an energy-dependent pulsed fraction varying from ~0.15 at 0.3 keV to ~0.6 at 1 keV. No evidence is found for simultaneous X-ray and radio mode switching. The total X-ray spectrum consists of a cool component (T ~0.96 × 106 K, hotspot radius R ~2.0 km) and a hot component (T ~2.2 × 106 K, R ~100 m). The hot component can be ascribed to the pulsed emission and the cool component to the unpulsed emission. The high-energy characteristics of PSR B1822–09 resemble those of middle-aged pulsars such as PSR B0656+14, PSR B1055–52 and Geminga, including an indication for pulsed high-energy gamma-ray emission in Fermi Large Area Telescope data. Explanations for the high pulsed fraction seem to require different temperatures at the two poles of this orthogonal rotator, or magnetic anisotropic beaming effects in its strong magnetic field. In our X-ray skymap, we found a harder source at only 5.1 ± 0.5 arcsec from PSR B1822–09, which might be a pulsar wind nebula.

  5. Vibration-Rotation Relaxation Using Mode Locked and Q-Switch Gas Lasers.

    DTIC Science & Technology

    equilibration of the vibrational modes among themselves is typically 100-1000 times faster than the rate of equilibration of the vibrational degrees of...been developed which provides insight into the paths by which the vibrational modes of this molecule come into equilibrium with each other. Such maps

  6. A novel approach for state of charge estimation based on adaptive switching gain sliding mode observer in electric vehicles

    NASA Astrophysics Data System (ADS)

    Chen, Xiaopeng; Shen, Weixiang; Cao, Zhenwei; Kapoor, Ajay

    2014-01-01

    In this paper, a novel approach for battery state of charge (SOC) estimation in electric vehicles (EVs) based on an adaptive switching gain sliding mode observer (ASGSMO) has been presented. To design the ASGSMO for the SOC estimation, the state equations based on a battery equivalent circuit model (BECM) are derived to represent dynamic behaviours of a battery. Comparing with a conventional sliding mode observer, the ASGSMO has a capability of minimising chattering levels in the SOC estimation by using the self-adjusted switching gain while maintaining the characteristics of being able to compensate modelling errors caused by the parameter variations of the BECM. Lyapunov stability theory is adopted to prove the error convergence of the ASGSMO for the SOC estimation. The lithium-polymer battery (LiPB) is utilised to conduct experiments for determining the parameters of the BECM and verifying the effectiveness of the proposed ASGSMO in various discharge current profiles including EV driving conditions in both city and suburban.

  7. A new asymmetric directional microphone algorithm with automatic mode-switching ability for binaural hearing support devices.

    PubMed

    Kim, Jinryoul; Nam, Kyoung Won; Yook, Sunhyun; Jang, Dong Pyo; Kim, In Young; Hong, Sung Hwa

    2015-06-01

    For hearing support devices, it is important to minimize the negative effect of ambient noises for speech recognition but also, at the same time, supply natural ambient sounds to the hearing-impaired person. However, conventional fixed bilateral asymmetric directional microphone (DM) algorithms cannot perform in such a way when the DM-mode device and a dominant noise (DN) source are placed on the same lateral hemisphere. In this study, a new binaural asymmetric DM algorithm that can overcome the defects of conventional algorithms is proposed. The proposed algorithm can estimate the position of a specific DN in the 90°-270° range and switch directional- and omnidirectional-mode devices automatically if the DM-mode device and the DN are placed in opposite lateral hemispheres. Computer simulation and KEMAR mannequin recording tests demonstrated that the performance of the conventional algorithm deteriorated when the DM-mode device and the DN were placed in the opposite hemisphere; in contrast, the performance of the proposed algorithm was consistently maintained regardless of directional variations in the DN. Based on these experimental results, the proposed algorithm may be able to improve speech quality and intelligibility for hearing-impaired persons who have similar degrees of hearing impairment in both ears.

  8. Optically-induced switching between mode-locked and unmode-locked continuous wave regimes of a femtosecond Cr4+:forsterite laser

    NASA Astrophysics Data System (ADS)

    Walsh, D. A.; Crombie, C. E.; Sibbett, W.; Brown, C. T. A.; Savitski, V. G.; Burns, D.; Calvez, S.

    2012-06-01

    The ability to control the temporal output from a femtosecond laser can enable the same laser to be used for multiple functions, for example, the laser used in an optical tweezers system could be used as a constant-intensity source to trap a biological cell and then be temporarily switched to mode-locked operation to effect photoporation. Here, we report the rapid switching of a Cr4+:forsterite laser between mode-locked and unmode-locked continuous wave (CW) regimes via the optical pumping of an intracavity SESAM element. Mode-locking of the laser was initiated by an intracavity quantum well (GaInAsN) SESAM having an anti-resonant design (ΔR~0.3%, λPL~1310nm) that yielded transform-limited 89fs pulses centered around 1296nm with a repetition rate of 162MHz at an average power of 64mW. Upon excitation of the SESAM with 600mW of extra-cavity power from an 808nm semiconductor diode laser, switching could be induced between the unmode-locked and mode-locked regimes. Transitions free of Q-switching or relaxation oscillations were observed with <200μs switching times for both for the initiation and cessation of mode-locking. Periods of mode-locked operation of custom duration could be produced by appropriate control of the SESAM pump diode enabling the generation of bursts of pulses as short as 400μs. Switching was confirmed to originate from local pump-induced heating of the SESAM by observing the laser going through identical regime switching when the chip temperature of the 'unpumped' SESAM was raised by ~20°C.

  9. Polarization switching and polarization mode hopping in quantum dot vertical-cavity surface-emitting lasers.

    PubMed

    Olejniczak, Lukasz; Panajotov, Krassimir; Thienpont, Hugo; Sciamanna, Marc; Mutig, Alex; Hopfer, Friedhelm; Bimberg, Dieter

    2011-01-31

    We show experimentally that polarization mode hopping in quantum dot vertical cavity surface emitting lasers (VCSELs) takes place between nonorthogonal elliptically polarized modes. In contrast to quantum well VCSELs the average dwell time decreases with injection current. This decrease is by 8 orders of magnitude: from seconds to nanoseconds and is achieved without any modifications of the VCSEL internal anisotropies. The observed scaling happens in a range of currents as wide as 8 times the threshold value.

  10. An improved switching converter model using discrete and average techniques

    NASA Technical Reports Server (NTRS)

    Shortt, D. J.; Lee, F. C.

    1982-01-01

    The nonlinear modeling and analysis of dc-dc converters has been done by averaging and discrete-sampling techniques. The averaging technique is simple, but inaccurate as the modulation frequencies approach the theoretical limit of one-half the switching frequency. The discrete technique is accurate even at high frequencies, but is very complex and cumbersome. An improved model is developed by combining the aforementioned techniques. This new model is easy to implement in circuit and state variable forms and is accurate to the theoretical limit.

  11. Q-switched mode-locked erbium-doped fiber laser based on topological insulator Bi(2)Se(3) deposited fiber taper.

    PubMed

    Gao, Lei; Huang, Wei; Zhang, Jing Dong; Zhu, Tao; Zhang, Han; Zhao, Chu Jun; Zhang, Wei; Zhang, Hua

    2014-08-10

    We have demonstrated the passive Q-switching mode-locking operation in an erbium-doped fiber (EDF) laser by using topological insulator Bi(2)Se(3) deposited on fiber taper, whose damage threshold can be further increased by the large evanescent field interacting length. Due to the low saturation intensity, stable Q-switched mode-locked fiber lasers centered at 1562 nm can be generated at a pump power of 10 mW. The temporal and spectral characteristics for different pump strengths have also been investigated. To the best of our knowledge, it is the first time a Q-switched mode-locked EDF laser based on the fiber taper deposited by Bi(2)Se(3) was generated.

  12. Stochastic kinetic model of two component system signalling reveals all-or-none, graded and mixed mode stochastic switching responses.

    PubMed

    Kierzek, Andrzej M; Zhou, Lu; Wanner, Barry L

    2010-03-01

    Two-component systems (TCSs) are prevalent signal transduction systems in bacteria that control innumerable adaptive responses to environmental cues and host-pathogen interactions. We constructed a detailed stochastic kinetic model of two component signalling based on published data. Our model has been validated with flow cytometry data and used to examine reporter gene expression in response to extracellular signal strength. The model shows that, depending on the actual kinetic parameters, TCSs exhibit all-or-none, graded or mixed mode responses. In accordance with other studies, positively autoregulated TCSs exhibit all-or-none responses. Unexpectedly, our model revealed that TCSs lacking a positive feedback loop exhibit not only graded but also mixed mode responses, in which variation of the signal strength alters the level of gene expression in induced cells while the regulated gene continues to be expressed at the basal level in a substantial fraction of cells. The graded response of the TCS changes to mixed mode response by an increase of the translation initiation rate of the histidine kinase. Thus, a TCS is an evolvable design pattern capable of implementing deterministic regulation and stochastic switches associated with both graded and threshold responses. This has implications for understanding the emergence of population diversity in pathogenic bacteria and the design of genetic circuits in synthetic biology applications. The model is available in systems biology markup language (SBML) and systems biology graphical notation (SBGN) formats and can be used as a component of large-scale biochemical reaction network models.

  13. Coexistence of unipolar and bipolar modes in Ag/ZnO/Pt resistive switching memory with oxygen-vacancy and metal-Ag filaments

    NASA Astrophysics Data System (ADS)

    Ma, Han-Lu; Wang, Zhong-Qiang; Xu, Hai-Yang; Zhang, Lei; Zhao, Xiao-Ning; Han, Man-Shu; Ma, Jian-Gang; Liu, Yi-Chun

    2016-12-01

    In this study, the unipolar resistive switching (URS) and bipolar resistive switching (BRS) are demonstrated to be coexistent in the Ag/ZnO/Pt memory device, and both modes are observed to strongly depend on the polarity of forming voltage. The mechanisms of the URS and BRS behaviors could be attributed to the electric-field-induced migration of oxygen vacancies (VO) and metal-Ag conducting filaments (CFs) respectively, which are confirmed by investigating the temperature dependences of low resistance states in both modes. Furthermore, we compare the resistive switching (RS) characteristics (e.g., forming and switching voltages, reset current and resistance states) between these two modes based on VO- and Ag-CFs. The BRS mode shows better switching uniformity and lower power than the URS mode. Both of these modes exhibit good RS performances, including good retention, reliable cycling and high-speed switching. The result indicates that the coexistence of URS and BRS behaviors in a single device has great potential applications in future nonvolatile multi-level memory. Project supported by the National Natural Science Foundation of China for Excellent Young Scholars (Grant No. 51422201), the National Natural Science Foundation of China (Grant Nos. 51172041, 51372035, 11304035, 61574031, and 61404026), the National Basic Research Program of China (Grant No. 2012CB933703), the “111” Project, China (Grant No. B13013), the Fund from Jilin Province, China (Grant Nos. 20140520106JH and 20140201008GX), the Research Fund for the Doctoral Program of Higher Education, China (Grant No. 20130043110004), the Fundamental Research Funds for the Central Universities, China (Grant Nos. 2412015KJ008 and 2412016KJ003).

  14. Inappropriate implantable cardioverter-defibrillator magnet-mode switch induced by a laptop computer.

    PubMed

    Tiikkaja, Maria; Aro, Aapo; Alanko, Tommi; Lindholm, Harri; Hietanen, Maila

    2012-06-01

    An implantable cardioverter-defibrillator (ICD) experienced electromagnetic interference from a laptop computer's hard disk. The patient with the ICD was using his laptop computer at home while lying on his bed. The laptop was positioned on his chest, when he heard a beeping sound from the ICD, indicating magnet mode conversion. This situation was replicated in a controlled environment, and the conversion was found to be due to the static magnetic field produced by the laptop's hard disk. The ICD's conversion to magnet mode can be dangerous because it ends all tachyarrhythmia detections and therapies.

  15. Passively Q-switched and mode-locked dual-wavelength Nd:GGG laser with Cr4+:YAG as a saturable absorber

    NASA Astrophysics Data System (ADS)

    Chu, Hongwei; Zhao, Shengzhi; Li, Yufei; Yang, Kejian; Li, Guiqiu; Li, Dechun; Zhao, Jia; Qiao, Wenchao; Li, Tao; Feng, Chuansheng; Zhang, Haijuan

    2014-03-01

    By using neodymium-doped gadolinium gallium garnet (Nd:GGG) as a laser medium, a simultaneously passively Q-switched and mode-locked (QML) dual-wavelength laser with Cr4+:YAG as a saturable absorber is presented. The laser simultaneously oscillated at 1061 nm and 1063 nm, corresponding to a frequency difference of 0.53 THz. QML pulses with nearly 100% modulation depth were observed. The mode-locked pulse duration underneath the Q-switched envelope was estimated to be about 908 ps. The experimental results indicated that the dual-wavelength QML Nd:GGG laser can be an excellent candidate for the generation of THz waves.

  16. Diode-pumped simultaneously Q-switched and mode-locked YVO4/Nd:YVO4/YVO4 crystal self-Raman first-Stokes laser.

    PubMed

    Huang, Guoxi; Yu, Yongqin; Xie, Xiaohua; Zhang, Yufeng; Du, Chenlin

    2013-08-26

    A diode-end-pumped simultaneously Q-switched and modelocked self-Raman YVO(4)/Nd:YVO(4)/YVO(4) laser at first-Stokes wavelength of 1175.9 nm was demonstrated. The shortest mode-locked pulse width of the laser was obtained to be ~23.57 ps, with the corresponding timebandwidth product of ~0.51. The maximum average output power, the highest pulse energy and the highest peak power were obtained to be 1.83 W, 6.1 μJ and 220 kW, respectively. The nonlinear Raman process improved the Q-switched mode-locking performance of the Stokes pulses.

  17. Time dependent Bloch mode transmittance in self-assembled random photonic crystal for photonic time delay switching

    NASA Astrophysics Data System (ADS)

    Bingi, Jayachandra; Nair, Radhika V.; Vijayan, C.

    2017-02-01

    Light propagation and localization in a random structure with a periodic background is an upcoming paradigm for novel photonic applications. This paper demonstrates the phenomenon of time dependent transmittance of evanescent Bloch modes (EBM) in ZnS random photonic crystal (RPC) which forms the basis for photonic delay switching. The RPC is fabricated by colloidal self-assembly with ZnS nanospheres of size 215 nm. An anomalous reciprocity and time dependent transmission at EBM (mid band gap wavelength) are observed in coherent back scattering and transmission studies respectively. These are explained on the basis of restricted propagation of EBMs through random channels in the periodic background and enhanced field storage inside RPC. The channelized propagation of EBMs is evident from decreasing time delay of transmittance at reduced thicknesses. The proportionality between transmission time delay and incident power confirms photon (field) storage within the RPC. The results indicate that structures with systematically engineered EBM channels can work as wavelength selective delay switch and further provide a short time photon storage system under non-absorbing conditions.

  18. Mode-locking and Q-switching in multi-wavelength fiber ring laser using low frequency phase modulation.

    PubMed

    Jun, Chang Su; Kim, Byoung Yoon

    2011-03-28

    We describe experimental investigation of pulsed output from a multi-wavelength fiber ring laser incorporating low frequency phase modulation with large modulation amplitude. The Erbium-doped fiber (EDF) ring laser generated more than 8 wavelength channels with the help of a phase modulator operating at 26.2 kHz and a periodic intra-cavity filter. For most cases, the laser output is pulsed in the form of mode-locking at 5.62 MHz and/or Q-switching at harmonic and sub-harmonic of the phase modulation frequency. Chaotic pulse output is also observed. The behavior of the output pulses are described as functions of pump power and phase modulation amplitude. The relative intensity noise (RIN) value of a single wavelength channel is measured to be under -100 dB/Hz (-140 dB/Hz beyond 1.5 GHz).

  19. Ubiquitination switches EphA2 vesicular traffic from a continuous safeguard to a finite signalling mode

    PubMed Central

    Sabet, Ola; Stockert, Rabea; Xouri, Georgia; Brüggemann, Yannick; Stanoev, Angel; Bastiaens, Philippe I. H.

    2015-01-01

    Autocatalytic phosphorylation of receptor tyrosine kinases (RTKs) enables diverse, context-dependent responses to extracellular signals but comes at the price of autonomous, ligand-independent activation. Using a conformational biosensor that reports on the kinase activity of the cell guidance ephrin receptor type-A (EphA2) in living cells, we observe that autonomous EphA2 activation is suppressed by vesicular recycling and dephosphorylation by protein tyrosine phosphatases 1B (PTP1B) near the pericentriolar recycling endosome. This spatial segregation of catalytically superior PTPs from RTKs at the plasma membrane is essential to preserve ligand responsiveness. Ligand-induced clustering, on the other hand, promotes phosphorylation of a c-Cbl docking site and ubiquitination of the receptor, thereby redirecting it to the late endosome/lysosome. We show that this switch from cyclic to unidirectional receptor trafficking converts a continuous suppressive safeguard mechanism into a transient ligand-responsive signalling mode. PMID:26292967

  20. Multiple-mode reconfigurable electro-optic switching network for optical fiber sensor array

    NASA Technical Reports Server (NTRS)

    Chen, Ray T.; Wang, Michael R.; Jannson, Tomasz; Baumbick, Robert

    1991-01-01

    This paper reports the first switching network compatible with multimode fibers. A one-to-many cascaded reconfigurable interconnection was built. A thin glass substrate was used as the guiding medium which provides not only higher coupling efficiency from multimode fiber to waveguide but also better tolerance of phase-matching conditions. Involvement of a total-internal-reflection hologram and multimode waveguide eliminates interface problems between fibers and waveguides. The DCG polymer graft has proven to be reliable from -180 C to +200 C. Survivability of such an electrooptic system in harsh environments is further ensured. LiNbO3 was chosen as the E-O material because of its stability at high temperatures (phase-transition temperature of more than 1000 C) and maturity of E-O device technology. Further theoretical calculation was conducted to provide the optimal interaction length and device capacitance.

  1. A Switched-Mode Breast Coil for 7 T MRI Using Forced-Current Excitation

    PubMed Central

    Bosshard, John C.; Rispoli, Joseph V.; Dimitrov, Ivan E.; Cheshkov, Sergey; McDougall, Mary Preston; Malloy, Craig; Wright, Steven M.

    2015-01-01

    In high-field magnetic resonance imaging, the radio frequency wavelength within the human body is comparable to anatomical dimensions, resulting in B1 inhomogeneity and nonuniform sensitivity patterns. Thus, this relatively short wavelength presents engineering challenges for RF coil design. In this study, a bilateral breast coil for 1H imaging at 7 T was designed and constructed using forced-current excitation. By forcing equal current through the coil elements, we reduce the effects of coupling between the elements to simplify tuning and to ensure a uniform field across both breasts. To combine the benefits of the higher power efficiency of a unilateral coil with the bilateral coverage of a bilateral coil, a switching circuit was implemented to allow the coil to be reconfigured for imaging the left, right, or both breasts. PMID:25706501

  2. Herd Those Sheep: Emergent Multiagent Coordination and Behavioral-Mode Switching.

    PubMed

    Nalepka, Patrick; Kallen, Rachel W; Chemero, Anthony; Saltzman, Elliot; Richardson, Michael J

    2017-05-01

    Effectively coordinating one's behaviors with those of others is essential for successful multiagent activity. In recent years, increased attention has been given to understanding the dynamical principles that underlie such coordination because of a growing interest in behavioral synchrony and complex-systems phenomena. Here, we examined the behavioral dynamics of a novel, multiagent shepherding task, in which pairs of individuals had to corral small herds of virtual sheep in the center of a virtual game field. Initially, all pairs adopted a complementary, search-and-recover mode of behavioral coordination, in which both members corralled sheep predominantly on their own sides of the field. Over the course of game play, however, a significant number of pairs spontaneously discovered a more effective mode of behavior: coupled oscillatory containment, in which both members synchronously oscillated around the sheep. Analysis and modeling revealed that both modes were defined by the task's underlying dynamics and, moreover, reflected context-specific realizations of the lawful dynamics that define functional shepherding behavior more generally.

  3. Switchable dual-wavelength Q-switched and mode-locked fiber lasers using a large-angle tilted fiber grating.

    PubMed

    Zhang, Zuxing; Mou, Chengbo; Yan, Zhijun; Wang, Yongjin; Zhou, Kaiming; Zhang, Lin

    2015-01-26

    We proposed and demonstrated pulsed fiber lasers Q-switched and mode-locked by using a large-angle tilted fiber grating, for the first time to our best knowledge. Owing to the unique polarization properties of the large-angle tilted fiber grating (LA-TFG), i.e. polarization-dependent loss and polarization-mode splitting, switchable dual-wavelength Q-switched and mode-locked pulses have been achieved with short and long cavities, respectively. For the mode-locking case, the laser was under the operation of nanosecond rectangular pulses, due to the peak-power clamping effect. With the increasing pump power, the durations of both single- and dual-wavelength rectangular pulses increase. It was also found that each filtered wavelength of the dual-wavelength rectangular pulse corresponds to an individual nanosecond rectangular pulse by employing a tunable bandpass filter.

  4. Optically controlled low-power on-off mode resonant tunneling oscillator with a heterojunction phototransistor switch.

    PubMed

    Lee, Kiwon; Park, Jaehong; Lee, Jooseok; Yang, Kyounghoon

    2015-03-15

    We report an optically controlled low-power on-off mode oscillator based on a resonant tunneling diode (RTD) that is monolithically integrated with a heterojunction phototransistor (HPT) optical switch. In order to achieve a low-power operation at a wavelength of 1.55 μm an InP-based quantum-effect tunneling diode is used for microwave signal generation based on a unique negative differential conductance (NDC) characteristic of the RTD at a low applied voltage. In addition, the high-gain HPT is used for converting incident optical data to an electrical data signal. The fabricated on-off mode oscillator shows a low-power consumption of 5 mW and a high-data-rate of 1  Gb/s at an oscillation frequency of 4.7 GHz. A good energy efficiency of 5  pJ/bit has been obtained due to the low DC power consumption along with high-data-rate performance of the RTD-based optoelectronic integration scheme.

  5. Switching sliding mode force tracking control of piezoelectric-hydraulic pump-based friction element actuation systems for automotive transmissions

    NASA Astrophysics Data System (ADS)

    Kim, Gi-Woo; Wang, K. W.

    2009-08-01

    In this study, a nonlinear sliding-mode controller is designed for force tracking of a piezoelectric-hydraulic pump (PHP)-based actuation system, which is developed to replace the current electro-hydraulic actuation systems for automatic transmission (AT) friction elements, such as band brakes or clutches. By utilizing the PHP, one can eliminate the various hydraulic components (oil pump, regulating valve and control valve) in current ATs and achieve a simpler configuration with more efficient operation. With the derived governing equation of motion of the PHP-based actuation system integrated with the friction element (band brake), a switching control law is synthesized based on the sliding-mode theory. To evaluate the effectiveness of the proposed control law, its force tracking performance for the engagement of a friction element during an AT 1\\to 2 up-shift is examined experimentally. It is shown that one can successfully track the desired force trajectory for AT shift control with small tracking error. This study demonstrates the potential of the PHP as a new controllable actuation system for AT friction elements.

  6. Structural Determinant for Switching between the Polymerase and Exonuclease Modes in the PCNA-Replicative DNA Polymerase Complex

    NASA Astrophysics Data System (ADS)

    Nishida, Hirokazu; Mayanagi, Kouta; Ishino, Yoshizumi; Morikawa, Kosuke

    Proliferating cell nuclear antigen (PCNA) is responsible for the processivity of DNA polymerase. We determined the crystal structure of Pyrococcus furiosus DNA polymerase (PfuPol) complexed with a cognate monomeric PCNA, which allowed us to construct a convincing model of the polymerase-PCNA ring interaction. Electron microscopy analyses confirmed that this complex structure exists among the multiple functional configurations in solution. Together with data from mutational analyses, this structural study indicated that the novel interaction between a stretched loop of PCNA and the PfuPol Thumb domain is quite important, in addition to the authentic PCNA-polymerase recognition site (PIP box). A comparison of the present structures with the previously reported structures of polymerases complexed with DNA suggested that the second interaction site plays a crucial role in switching between the polymerase and exonuclease modes, by stabilizing only the polymerase mode. This proposed mechanism of fidelity control of replicative DNA polymerases was supported by experiments, in which a mutation within the second interaction site caused an enhancement in the exonuclease activity in the presence of PCNA.

  7. Subducting-slab transition-zone interaction: Stagnation, penetration and mode switches

    NASA Astrophysics Data System (ADS)

    Agrusta, Roberto; Goes, Saskia; van Hunen, Jeroen

    2017-04-01

    Seismic tomography shows that subducting slabs can either sink straight into the lower mantle, or lie down in the mantle transition zone. Moreover, some slabs seem to have changed mode from stagnation to penetration or vice versa. We investigate the dynamic controls on these modes and particularly the transition between them using 2D self-consistent thermo-mechanical subduction models. Our models confirm that the ability of the trench to move is key for slab flattening in the transition zone. Over a wide range of plausible Clapeyron slopes and viscosity jumps at the base of the transition zone, hot young slabs (25 Myr in our models) are most likely to penetrate, while cold old slabs (150 Myr) drive more trench motion and tend to stagnate. Several mechanisms are able to induce penetrating slabs to stagnate: ageing of the subducting plate, decreasing upper plate forcing, and increasing Clapeyron slope (e.g. due to the arrival of a more hydrated slab). Getting stagnating slabs to penetrate is more difficult. It can be accomplished by an instantaneous change in the forcing of the upper plate from free to motionless, or a sudden decrease in the Clapeyron slope. A rapid change in plate age at the trench from old to young cannot easily induce penetration. On Earth, ageing of the subducting plate (with accompanying upper plate rifting) may be the most common mechanism for causing slab stagnation, while strong changes in upper plate forcing appear required for triggering slab penetration.

  8. Substitution of tryptophan 89 with tyrosine switches the DNA binding mode of PC4.

    PubMed

    Huang, Jinguang; Zhao, Yanxiang; Liu, Huaian; Huang, Dan; Cheng, Xiankun; Zhao, Wensheng; Taylor, Ian A; Liu, Junfeng; Peng, You-Liang

    2015-03-05

    PC4, a well-known general transcription cofactor, has multiple functions in transcription and DNA repair. Residue W89, is engaged in stacking interactions with DNA in PC4, but substituted by tyrosine in some PC4 orthologous proteins. In order to understand the consequences and reveal the molecular details of this substitution we have determined the crystal structures of the PC4 orthologue MoSub1 and a PC4 W89Y mutant in complex with DNA. In the structure of MoSub1-DNA complex, Y74 interacts directly with a single nucleotide of oligo DNA. By comparison, the equivalent residue, W89 in wild type PC4 interacts with two nucleotides and the base of the second nucleotide has distinct orientation relative to that of the first one. A hydrophobic patch around W89 that favours interaction with two nucleotides is not formed in the PC4 W89Y mutant. Therefore, the change of the surface hydrophobicity around residue 89 results in a difference between the modes of DNA interaction. These results indicate that the conserved Y74 in MoSub1 or W89 in PC4, are not only key residues in making specific interactions with DNA but also required to determine the DNA binding mode of PC4 proteins.

  9. Optical parametric generation by a simultaneously Q-switched mode-locked single-oscillator thulium-doped fiber laser in orientation-patterned gallium arsenide.

    PubMed

    Donelan, Brenda; Kneis, Christian; Scurria, Giuseppe; Cadier, Benoît; Robin, Thierry; Lallier, Eric; Grisard, Arnaud; Gérard, Bruno; Eichhorn, Marc; Kieleck, Christelle

    2016-11-01

    Optical parametric generation is demonstrated in orientation-patterned gallium arsenide, pumped by a novel single-oscillator simultaneously Q-switched and mode-locked thulium-doped fiber laser, downconverting the pump radiation into the mid-infrared wavelength regime. The maximum output energy reached is greater than 2.0 μJ per pump pulse.

  10. Switching from pure- into simple-shear mode during uplift of the Altiplano plateau (Central Andes)

    NASA Astrophysics Data System (ADS)

    Babeyko, A. Yu.; Sobolev, S. V.

    2003-04-01

    The Altiplano plateau of the Central Andes is the second greatest plateau in the world after Tibet with an average elevation of about 4 km formed as a result of ocean-continent collision between subducting Nasca plate on the west and Brazilian shield on the east. According to the well known Isacks (1988) scenario, the Cenozoic evolution of the plateau started ca. 30 Ma in response to the retreat of the flat-subducted Nasca plate. Astenospheric material, which replaced the retreated plate, thermally thinned and softened the overlying lithosphere. The Altiplano crust, being pushed by the Brazilian shield from the east, was first shortened in a pure-shear mode and reached 60-70 km in thickness. At ca. 8-10 Ma deformation changed to a simple-shear mode: it was ceased in the upper crust of the plateau and migrated eastwards, into the Subandean, while the plateau itself continued to grow due to ongoing shortening in the lower crust. We employ numerical 2D thermomechanical modelling to test the above scenario and to evaluate the key parameters, which account for the transition from pure- to simple- shear style of the lithosphere-scale deformation under pure-shear boundary condition. As a numerical tool we use explicit finite difference/finite element lagrangian code with markers tracking material properties. The model contains rheologically different layers representing sediments, felsic and mafic crust, lithospheric mantle, and astenosphere. Rheological laws are Mohr-Coloumb elasto-plastic with softening and Maxwell visco-elastic with nonlinear power-law creep. Initial and boundary conditions simulate thermal activation of the Altiplano lithosphere by upwelling astenosphere as well as its westward pushing by the cold Brazilian shield with constant velocity. We found that model shortening always occurs in a pure-shear mode unless the uppermost crust of the Brazilian shield becomes during the deformation considerably weaker than the Altiplano upper crust (drop of friction

  11. Poliovirus Switches to an eIF2-Independent Mode of Translation during Infection▿

    PubMed Central

    White, James P.; Reineke, Lucas C.; Lloyd, Richard E.

    2011-01-01

    Inhibition of translation is an integral component of the innate antiviral response and is largely accomplished via interferon-activated phosphorylation of the α subunit of eukaryotic initiation factor 2 (eIF2α). To successfully infect a host, a virus must overcome this blockage by either controlling eIF2α phosphorylation or by utilizing a noncanonical mode of translation initiation. Here we show that enterovirus RNA is sensitive to translation inhibition resulting from eIF2α phosphorylation, but it becomes resistant as infection progresses. Further, we show that the cleavage of initiation factor eIF5B during enteroviral infection, along with the viral internal ribosome entry site, plays a role in mediating viral translation under conditions that are nonpermissive for host cell translation. Together, these results provide a mechanism by which enteroviruses evade the antiviral response and provide insight into a noncanonical mechanism of translation initiation. PMID:21697471

  12. Generation of Q-switched mode locking controlled rectangular noise-like soliton bunching in a Tm-doped fiber laser.

    PubMed

    Qiao, Tian; Chen, Weicheng; Lin, Wei; Yang, Zhongmin

    2016-08-08

    We report on an interesting phenomenon of the combination of Q-switched mode locked pulses (QSMLP) and rectangular noise-like pulses (RNLP) as a unit in a Tm-doped ring fiber laser which contains a Fabry-Perot (F-P) subcavity based on the nonlinear polarization evolution (NPE) technique. The RNLP and QSMLP are independently generated in the ring cavity and F-P subcavity, respectively. A notable characteristic is that the physical parameters of RNLP, e.g. repetition rate and pulse duration, are controlled by QSMLP. Thus, they form as a composite bunching, which is termed as "Q-switched mode locking controlled rectangular noise-like soliton bunching (QRNSB)". Further investigation shows that the existence of QRNSB only occurs in high pumping conditions, while both fundamental mode-locking pulses and the coexistence of QSMLP and solitons are achieved in low pumping ones. Our work can enrich the understanding of the nonlinear dynamics in fiber lasers.

  13. As-grown uniform MoS2/mica saturable absorber for passively Q-switched mode-locked Nd:GdVO4 laser

    NASA Astrophysics Data System (ADS)

    Xu, Yuanyuan; Yang, Cheng; Ge, Pengguang; Liu, Jie; Jiang, Shouzhen; Li, Chun; Man, Baoyuan

    2016-08-01

    Molybdenum disulfide (MoS2) has recently attracted growing attention due to its distinctive properties and potential applications in optoelectronics and electronics. Here, large-area and high-quality MoS2 film with uniform thickness was obtained by thermally decomposing ammonium thiomolybdate. Besides, it is firstly demonstrated that the as-grown MoS2/mica can be directly inserted into Nd:GdVO4 laser cavity as saturable absorber for the output of diode-pumped passively Q-switched mode-locked pulse trains. Using the MoS2 saturable absorbers, the stable Q-switched mode-locked pulse trains with high modulation depth were realized, suggesting that the broadband MoS2 SA could potentially be employed in mode-locking laser system

  14. TRPV1 activation power can switch an action mode for its polypeptide ligands.

    PubMed

    Nikolaev, Maxim V; Dorofeeva, Natalia A; Komarova, Margarita S; Korolkova, Yuliya V; Andreev, Yaroslav A; Mosharova, Irina V; Grishin, Eugene V; Tikhonov, Denis B; Kozlov, Sergey A

    2017-01-01

    TRPV1 (vanilloid) receptors are activated by different types of stimuli including capsaicin, acidification and heat. Various ligands demonstrate stimulus-dependent action on TRPV1. In the present work we studied the action of polypeptides isolated from sea anemone Heteractis crispa (APHC1, APHC2 and APHC3) on rat TRPV1 receptors stably expressed in CHO cells using electrophysiological recordings, fluorescent Ca2+ measurements and molecular modeling. The APHCs potentiated TRPV1 responses to low (3-300 nM) concentrations of capsaicin but inhibited responses to high (>3.0 μM) concentrations. The activity-dependent action was also found for TRPV1 responses to 2APB and acidification. Thus the action mode of APHCs is bimodal and depended on the activation stimuli strength-potentiation of low-amplitude responses and no effect/inhibition of high-amplitude responses. The double-gate model of TRPV1 activation suggests that APHC-polypeptides may stabilize an intermediate state during the receptor activation. Molecular modeling revealed putative binding site at the outer loops of TRPV1. Binding to this site can directly affect activation by protons and can be allosterically coupled with capsaicin site. The results are important for further investigations of both TRPV1 and its ligands for potential therapeutic use.

  15. "Molecular Switches" on mGluR Allosteric Ligands That Modulate Modes of Pharmacology

    PubMed Central

    Wood, Michael R.; Hopkins, Corey R.; Brogan, John T.; Conn, P. Jeffrey; Lindsley, Craig W.

    2013-01-01

    G-Protein-coupled receptors (GPCRs) represent the largest class of drug targets, accounting for more than 40% of marketed drugs; however, discovery efforts for many GPCRs have failed to provide viable drug candidates. Historically, drug discovery efforts have focused on developing ligands that act at the orthosteric site of the endogenous agonist. Recently, efforts have focused on functional assay paradigms and the discovery of ligands that act at allosteric sites to modulate receptor function in either a positive, negative, or neutral manner. Allosteric modulators have numerous advantages over orthosteric ligands, including high subtype selectivity; the ability to mimic physiological conditions; the lack of densensitization, downregulation, and internalization; and reduced side effects. Despite these virtues, challenging issues have now arisen for allosteric modulators of metabotropic glutamate receptors (mGluRs): shallow SAR, ligand-directed trafficking, and the identification of subtle “molecular switches” that modulate the modes of pharmacology. Here, we will discuss the impact of modest structural changes to multiple mGluR allosteric ligands scaffolds that unexpectedly modulate pharmacology and raise concerns over metabolism and the pharmacology of metabolites. PMID:21341760

  16. Liquid Nitrogen Temperature Operation of a Switching Power Converter

    NASA Technical Reports Server (NTRS)

    Ray, Biswajit; Gerber, Scott S.; Patterson, Richard L.; Myers, Ira T.

    1995-01-01

    The performance of a 42/28 V, 175 W, 50 kHz pulse-width modulated buck dc/dc switching power converter at liquid nitrogen temperature (LNT) is compared with room temperature operation. The power circuit as well as the control circuit of the converter, designed with commercially available components, were operated at LNT and resulted in a slight improvement in converter efficiency. The improvement in power MOSFET operation was offset by deteriorating performance of the output diode rectifier at LNT. Performance of the converter could be further improved at low temperatures by using only power MOSFET's as switches. The use of a resonant topology will further improve the circuit performance by reducing the switching noise and loss.

  17. Dynamical modeling and experiment for an intra-cavity optical parametric oscillator pumped by a Q-switched self-mode-locking laser

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Liu, Nianqiao; Song, Peng; Zhang, Haikun

    2016-11-01

    The rate-equation-based model for the Q-switched mode-locking (QML) intra-cavity OPO (IOPO) is developed, which includes the behavior of the fundamental laser. The intensity fluctuation mechanism of the fundamental laser is first introduced into the dynamics of a mode-locking OPO. In the derived model, the OPO nonlinear conversion is considered as a loss for the fundamental laser and thus the QML signal profile originates from the QML fundamental laser. The rate equations are solved by a digital computer for the case of an IOPO pumped by an electro-optic (EO) Q-switched self-mode-locking fundamental laser. The simulated results for the temporal shape with 20 kHz EO repetition and 11.25 W pump power, the signal average power, the Q-switched pulsewidth and the Q-switched pulse energy are obtained from the rate equations. The signal trace and output power from an EO QML Nd3+: GdVO4/KTA IOPO are experimentally measured. The theoretical values from the rate equations agree with the experimental results well. The developed model explains the behavior, which is helpful to system optimization.

  18. Substrate Binding Mode and Molecular Basis of a Specificity Switch in Oxalate Decarboxylase

    PubMed Central

    2016-01-01

    Oxalate decarboxylase (OxDC) catalyzes the conversion of oxalate into formate and carbon dioxide in a remarkable reaction that requires manganese and dioxygen. Previous studies have shown that replacing an active-site loop segment Ser161-Glu162-Asn163-Ser164 in the N-terminal domain of OxDC with the cognate residues Asp161-Ala162-Ser-163-Asn164 of an evolutionarily related, Mn-dependent oxalate oxidase gives a chimeric variant (DASN) that exhibits significantly increased oxidase activity. The mechanistic basis for this change in activity has now been investigated using membrane inlet mass spectrometry (MIMS) and isotope effect (IE) measurements. Quantitative analysis of the reaction stoichiometry as a function of oxalate concentration, as determined by MIMS, suggests that the increased oxidase activity of the DASN OxDC variant is associated with only a small fraction of the enzyme molecules in solution. In addition, IE measurements show that C–C bond cleavage in the DASN OxDC variant proceeds via the same mechanism as in the wild-type enzyme, even though the Glu162 side chain is absent. Thus, replacement of the loop residues does not modulate the chemistry of the enzyme-bound Mn(II) ion. Taken together, these results raise the possibility that the observed oxidase activity of the DASN OxDC variant arises from an increased level of access of the solvent to the active site during catalysis, implying that the functional role of Glu162 is to control loop conformation. A 2.6 Å resolution X-ray crystal structure of a complex between oxalate and the Co(II)-substituted ΔE162 OxDC variant, in which Glu162 has been deleted from the active site loop, reveals the likely mode by which the substrate coordinates the catalytically active Mn ion prior to C–C bond cleavage. The “end-on” conformation of oxalate observed in the structure is consistent with the previously published V/K IE data and provides an empty coordination site for the dioxygen ligand that is thought to

  19. Structural determinant for switching between the polymerase and exonuclease modes in the PCNA-replicative DNA polymerase complex

    PubMed Central

    Nishida, Hirokazu; Mayanagi, Kouta; Kiyonari, Shinichi; Sato, Yuichi; Oyama, Takuji; Ishino, Yoshizumi; Morikawa, Kosuke

    2009-01-01

    Proliferating cell nuclear antigen (PCNA) is responsible for the processivity of DNA polymerase. We determined the crystal structure of Pyrococcus furiosus DNA polymerase (PfuPol) complexed with the cognate monomeric PCNA, which allowed us to construct a convincing model of the polymerase-PCNA ring interaction, with unprecedented configurations of the two molecules. Electron microscopic analyses indicated that this complex structure exists in solution. Our structural study revealed that an interaction occurs between a stretched loop of PCNA and the PfuPol Thumb domain, in addition to the authentic PCNA-polymerase recognition site (PIP box). Comparisons of the present structure with the previously reported structures of polymerases complexed with DNA, suggested that the second interaction plays a crucial role in switching between the polymerase and exonuclease modes, by inducing a PCNA-polymerase complex configuration that favors synthesis over editing. This putative mechanism for fidelity control of replicative DNA polymerases is supported by experiments, in which mutations at the second interaction site caused enhancements in the exonuclease activity in the presence of PCNA. PMID:19934045

  20. Enhancement of viewing angle properties of a single-domain fringe-field switching mode using zero pretilt alignment

    NASA Astrophysics Data System (ADS)

    Oh, Seong-Woo; Lee, Dong-Jin; Park, Min-Kyu; Park, Kyoung Ho; Lee, Joun-Ho; Kim, Byeong Koo; Kim, Hak-Rin

    2015-10-01

    We demonstrated the effect of the pretilt angle on the viewing angle properties of the single-domain fringe-field switching (FFS) mode, and proposed a method to enhance the viewing angle properties. Firstly, we investigated the origin of the asymmetric viewing angle problems in the field-on and off states by performing a field-induced liquid crystal (LC) reorientation analysis. Because of the asymmetric properties induced by the coupling between the tilting angle of the LC director and the polar component of the electric field, a zero pretilt angle is essential for the symmetric viewing angle properties. Secondly, to eliminate the pretilt angle, which is generally inevitable with the rubbing process, we applied polystyrene (PS) alignment layer which generates an easy axis perpendicular to the rubbing direction. Azimuthal anchoring energy and thermal stability of the PS layer were improved by employing UV-curable reactive mesogen (RM) within the LC cell. The RM-stabilized PS layer preserved the zero pretilt angle with enhanced thermal stability. Finally, by evaluating 2.4 in QVGA single-domain FFS LC cells, we confirmed the improved alignment ability of the RM-stabilized PS layer and the effect of the zero pretilt angle on electro-optical properties such as response time and viewing angle.

  1. Treatment of Melasma with the Photoacoustic Twin Pulse Mode of Low-Fluence 1,064 nm Q-Switched Nd:YAG Laser.

    PubMed

    Kim, Jee Young; Choi, Misoo; Nam, Chan Hee; Kim, Ji Seok; Kim, Myung Hwa; Park, Byung Cheol; Hong, Seung Phil

    2016-06-01

    Low-fluence 1,064 nm Q-switched Nd:YAG laser has been widely used for the treatment of melasma. Although new Q-switched Nd:YAG lasers with photoacoustic twin pulse (PTP) mode have been recently developed for high-efficiency, there is limited information available for the new technique. This study was designed to investigate the efficacy and adverse effects after few sessions of repeated low fluence 1,064 nm Q-switched Nd:YAG laser treatment with PTP mode in Asian women with melasma. Twenty-two Korean women were treated with a total of five sessions of low-fluence PTP mode Nd:YAG laser treatment (Pastelle®) at 2 weeks interval. Responses to treatments were evaluated by using Melasma Area and Severity Index (MASI) scoring, colorimeter measurement, and the investigators' and patients' overall assessments. Adverse events were recorded at each visit. Investigators' and patients' overall assessment showed that 'significantly improved' was assessed by 13 (59.1%) and 19 of 22 patients (86.4%), respectively. MASI scores were significantly reduced by 20.4%. The lightness, measured by using a colorimeter, was significantly increased by 1.3 point. Notable adverse events were not observed. After 5 sessions of laser therapy alone, about 60% of the subjects showed significant improvement. Few sessions of repeated laser toning treatment using the PTP mode is a safe and effective way to treat facial melasma.

  2. Treatment of Melasma with the Photoacoustic Twin Pulse Mode of Low-Fluence 1,064 nm Q-Switched Nd:YAG Laser

    PubMed Central

    Kim, Jee Young; Choi, Misoo; Nam, Chan Hee; Kim, Ji Seok; Kim, Myung Hwa; Park, Byung Cheol

    2016-01-01

    Background Low-fluence 1,064 nm Q-switched Nd:YAG laser has been widely used for the treatment of melasma. Although new Q-switched Nd:YAG lasers with photoacoustic twin pulse (PTP) mode have been recently developed for high-efficiency, there is limited information available for the new technique. Objective This study was designed to investigate the efficacy and adverse effects after few sessions of repeated low fluence 1,064 nm Q-switched Nd:YAG laser treatment with PTP mode in Asian women with melasma. Methods Twenty-two Korean women were treated with a total of five sessions of low-fluence PTP mode Nd:YAG laser treatment (Pastelle®) at 2 weeks interval. Responses to treatments were evaluated by using Melasma Area and Severity Index (MASI) scoring, colorimeter measurement, and the investigators' and patients' overall assessments. Adverse events were recorded at each visit. Results Investigators' and patients' overall assessment showed that 'significantly improved' was assessed by 13 (59.1%) and 19 of 22 patients (86.4%), respectively. MASI scores were significantly reduced by 20.4%. The lightness, measured by using a colorimeter, was significantly increased by 1.3 point. Notable adverse events were not observed. Conclusion After 5 sessions of laser therapy alone, about 60% of the subjects showed significant improvement. Few sessions of repeated laser toning treatment using the PTP mode is a safe and effective way to treat facial melasma. PMID:27274626

  3. Diode-pumped passively Q-switched and mode-locked Nd:GdVO4 laser at 1.34 microm with V:YAG saturable absorber.

    PubMed

    Yang, Kejian; Zhao, Shengzhi; He, Jingliang; Zhang, Baitao; Zuo, Chunhua; Li, Guiqiu; Li, Dechun; Li, Ming

    2008-12-08

    Using V:YAG as the saturable absorber, a diode-pumped passively Q-switched and mode-locked Nd:GdVO(4) laser at 1.34 microm is realized. Nearly 100% modulation depth of mode-locking has been achieved. The width of the mode-locked pulse is estimated to be less than 460 ps with 125 MHz repetition rate within an about 1 micros-long Q-switched pulse envelope. A maximum output power of 220 mW and Q-switched pulse energy of 10.5 microJ is obtained. Using the hyperbolic secant function methods, a fluctuation rate equation model considering the Gaussian distribution of the intracavity photon density and the population inversion in the gain medium as well as the ground-state population intensity of the saturable absorber has been proposed to describe the mode-locking process of diode-pumped Nd:GdVO(4)/V(3+):YAG laser. With the space-dependent rate equations solved numerically, the theoretical calculations reproduce the laser characteristics well.

  4. Application of small-signal modeling and measurement techniques to the stability analysis of an integrated switching-mode power system. [onboard Dynamics Explorer Satellite

    NASA Technical Reports Server (NTRS)

    Wong, R. C.; Owen, H. A., Jr.; Wilson, T. G.; Rodriguez, G. E.

    1980-01-01

    Small-signal modeling techniques are used in a system stability analysis of a breadboard version of a complete functional electrical power system. The system consists of a regulated switching dc-to-dc converter, a solar-cell-array simulator, a solar-array EMI filter, battery chargers and linear shunt regulators. Loss mechanisms in the converter power stage, including switching-time effects in the semiconductor elements, are incorporated into the modeling procedure to provide an accurate representation of the system without requiring frequency-domain measurements to determine the damping factor. The small-signal system model is validated by the use of special measurement techniques which are adapted to the poor signal-to-noise ratio encountered in switching-mode systems. The complete electrical power system with the solar-array EMI filter is shown to be stable over the intended range of operation.

  5. Investigations of Q-switching and mode locking in diode-pumped Nd:YVO4 laser with passive saturable absorbers

    NASA Astrophysics Data System (ADS)

    Kwiatkowski, Jacek; Jabczynski, Jan K.; Zendzian, Waldemar

    2005-03-01

    The saturable absorbers (Cr4+:YAG, GaAs and LiF crystals for 1064-nm wavelength, V3+:YAG crystals for 1340-nm respectively) were examined as passive Mode Lockers and Q-switches in diode pumped Nd:YVO4 lasers in the Z-type resonators. In each case, partially modulated long trains of QML pulses were observed. As a rule, envelopes with about 1 μs duration and more than 50% depth of modulation were observed. For stabilization of the mode locking trains nonlinear crystals (KTP or LBO) as negative feedback elements were inserted. The fully modulated QML trains for intracavity II harmonic conversion at 670-nm wavelength in V3+:YAG Q-switched Nd:YVO4 laser with LBO crystal were demonstrated.

  6. Optically controlled switch-mode current-source amplifiers for on-coil implementation in high-field parallel transmission.

    PubMed

    Gudino, Natalia; Duan, Qi; de Zwart, Jacco A; Murphy-Boesch, Joe; Dodd, Stephen J; Merkle, Hellmut; van Gelderen, Peter; Duyn, Jeff H

    2016-07-01

    We tested the feasibility of implementing parallel transmission (pTX) for high-field MRI using a radiofrequency (RF) amplifier design to be located on or in the immediate vicinity of an RF transmit coil. We designed a current-source switch-mode amplifier based on miniaturized, nonmagnetic electronics. Optical RF carrier and envelope signals to control the amplifier were derived, through a custom-built interface, from the RF source accessible in the scanner control. Amplifier performance was tested by benchtop measurements as well as with imaging at 7T (300 MHz) and 11.7 T (500 MHz). The ability to perform pTX was evaluated by measuring interchannel coupling and phase adjustment in a two-channel setup. The amplifier delivered in excess of 44 W RF power and caused minimal interference with MRI. The interface derived accurate optical control signals with carrier frequencies ranging from 64 to 750 MHz. Decoupling better than 14 dB was obtained between two coil loops separated by only 1 cm. Application to MRI was demonstrated by acquiring artifact-free images at 7 T and 11.7 T. We propose an optically controlled miniaturized RF amplifier for on-coil implementation at high fields that should facilitate implementation of high-density pTX arrays. Magn Reson Med 76:340-349, 2016. Published 2015. This article is a U.S. Government work and is in the public domain in the USA. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

  7. Linearly polarized pumped passively Q-switched Nd:YVO4 microchip laser for Ince-Gaussian laser modes with controllable orientations

    NASA Astrophysics Data System (ADS)

    He, Hong-Sen; Zhang, Ming-Ming; Dong, Jun; Ueda, Ken-Ichi

    2016-12-01

    A tilted, linearly polarized laser diode end-pumped Cr4+:YAG passively Q-switched a-cut Nd:YVO4 microchip laser for generating numerous Ince-Gaussian (IG) laser modes with controllable orientations has been demonstrated by selecting the crystalline orientation of an a-cut Nd:YVO4 crystal. The same IG laser mode with different orientations has been achieved with the same absorbed pump power in a passively Q-switched Nd:YVO4 microchip laser under linearly polarized pumping when the incident pump power and the crystalline orientation of an a-cut Nd:YVO4 crystal are both properly selected. The significant improvement of pulsed laser performance of controllable IG modes has been achieved by selecting the crystalline orientation of an a-cut Nd:YVO4 crystal. The maximum pulse energy is obtained along the a-axis of an a-cut Nd:YVO4 crystal and the highest peak power is achieved along the c-axis of an a-cut Nd:YVO4 crystal, respectively, which has potential applications on quantum computation and optical manipulation. The generation of controllable IG laser modes in microchip lasers under linearly polarized pumping provides a convenient and universal way to control IG laser mode numbers with anisotropic crystal as a gain medium.

  8. C-cut Nd-doped vanadate crystal self-Raman laser with narrow Q-switched envelope and high mode-locked repetition rate

    NASA Astrophysics Data System (ADS)

    Li, Zuo-han; Peng, Ji-ying; Zheng, Yi; Yang, Ye; Kou, Jin-hua

    2014-11-01

    In this paper, a passively Q-switched and mode-locked c-cut Nd-doped vanadate crystal self-Raman laser at 1.17 μm is firstly demonstrated by using Cr4+:YAG. Two crystals of Nd3+:YVO4 and Nd3+:GdVO4 are adopted to generate laser, respectively. With the incident pump power of 13 W, the average output powers of 678 mW and 852 mW at 1.17 μm are obtained with the durations of Q-switched envelope of 1.8 ns and 2 ns, respectively. The mode-locked repetition rates are as high as 2.3 Hz and 2.2 GHz, respectively. As far as we know, the Q-switched envelope is the narrowest and the mode-locked repetition rate is the highest at present in this field. In addition, yellow laser output is also achieved by using the LiB3O5 frequency doubling crystal.

  9. Optical switch

    DOEpatents

    Reedy, Robert P.

    1987-01-01

    An optical switching device (10) is provided whereby light from a first glass fiber (16) or a second glass fiber (14) may be selectively transmitted into a third glass fiber (18). Each glass fiber is provided with a focusing and collimating lens system (26, 28, 30). In one mode of operation, light from the first glass fiber (16) is reflected by a planar mirror (36) into the third glass fiber (18). In another mode of operation, light from the second glass fiber (14) passes directly into the third glass fiber (18). The planar mirror (36) is attached to a rotatable table (32) which is rotated to provide the optical switching.

  10. Optical switch

    DOEpatents

    Reedy, R.P.

    1987-11-10

    An optical switching device is provided whereby light from a first glass fiber or a second glass fiber may be selectively transmitted into a third glass fiber. Each glass fiber is provided with a focusing and collimating lens system. In one mode of operation, light from the first glass fiber is reflected by a planar mirror into the third glass fiber. In another mode of operation, light from the second glass fiber passes directly into the third glass fiber. The planar mirror is attached to a rotatable table which is rotated to provide the optical switching. 3 figs.

  11. Optical switch

    DOEpatents

    Reedy, R.P.

    1985-01-18

    An optical switching device is provided whereby light from a first glass fiber or a second glass fiber may be selectively transmitted into a third glass fiber. Each glass fiber is provided with a focusing and collimating lens system. In one mode of operation, light from the first glass fiber is reflected by a planar mirror into the third glass fiber. In another mode of operation, light from the second glass fiber passes directly into the third glass fiber. The planar mirror is attached to a rotatable table which is rotated to provide the optical switching.

  12. A Frequency Domain Approach for Controlling Fast-Scale Instabilities in Switching Power Converters

    NASA Astrophysics Data System (ADS)

    Rodriguez, E.; Alarcón, E.; Iu, H. H. C.; El Aroudi, A.

    This paper deals with controllers of fast-scale instabilities in DC-DC switching power converters from a frequency domain standpoint with the aim of understanding their working principle and hence simplifying their design. Some approaches for controlling fast-scale instabilities and their limitations are revisited. Considering the frequency domain transfer function of already existing controllers, a simple and extended notch filter centered at half of the switching frequency is proposed to avoid these instabilities. However, a switching converter under this controller may still exhibit the undesired slow-scale instability. Accordingly, the paper explores an alternative approach based on amplifying the harmonic at the switching frequency. Numerical simulations show that the new proposed controller can concurrently improve both fast-scale and slow-scale stability margins. The results from the different controllers are contrasted in terms of stability boundaries, indicating that the last one presents a wider stability range.

  13. Failure mode analysis of a spacecraft power system

    SciTech Connect

    Lee, J.R.

    1995-12-31

    For the spacecraft power system`s dynamic analyses, dc/dc converters are usually modeled with a linearized model using the state space averaging technique. The linearized model can be used for small-signal ac and transient analyses. However, since the linearized model has limitations in its accuracies, certain types of transient analyses including a failure mode must be performed by using a more accurate cycle-by-cycle model. In this paper, a failure mode analysis is presented with a small-signal analysis and corresponding transient simulations.

  14. Solid state lasers based on chromium- and neodymium-activated scandium garnets operating in the Q-switched mode

    NASA Astrophysics Data System (ADS)

    Denisov, A. L.; Zharikov, E. V.; Zavartsev, Iu. D.; Zagumennyi, A. I.; Lutts, G. B.

    1991-02-01

    The development of passively Q-switched and self-Q-switched lasers based on chromium-containing scandium garnets with phototropic centers is reported. The lasers operate over a wide frequency repetition rate with a mean output up to 100 W. The characteristics of phototropic absorption in the 1-micron region are examined, and the possibility of lasing at the weak transition of the Nd(3+) ion in chromium-containing scandium garnets with phototropic centers is discussed.

  15. R&D100: 6.5kV Enhancement-Mode Silicon Carbide JFET Switch

    ScienceCinema

    Dries, Chris; Hostetler, John; Atcitty, Stan

    2016-10-19

    Researchers at Sandia National Laboratories have partnered with United Silicon Carbide, Inc. to combine advanced materials with novel manufacturing ideas to build a new product for significantly more efficient power conversion. Harnessing the unique features of silicon carbide, this first of its kind device allows higher voltage switching, and reductions in switching losses to significantly boost the efficiency and reliability of power generation and power conversion.

  16. R&D100: 6.5kV Enhancement-Mode Silicon Carbide JFET Switch

    SciTech Connect

    Dries, Chris; Hostetler, John; Atcitty, Stan

    2015-11-19

    Researchers at Sandia National Laboratories have partnered with United Silicon Carbide, Inc. to combine advanced materials with novel manufacturing ideas to build a new product for significantly more efficient power conversion. Harnessing the unique features of silicon carbide, this first of its kind device allows higher voltage switching, and reductions in switching losses to significantly boost the efficiency and reliability of power generation and power conversion.

  17. Phase-inversion-based selective harmonic elimination (PI-SHE) in multi-level switched-mode tone- and frequency-modulated excitation.

    PubMed

    Cowell, David M J; Smith, Peter R; Freear, Steven

    2013-06-01

    Switched-mode operation allows the miniaturization of excitation circuitry but suffers from high harmonic distortion. This paper presents a method of phase-inversion-based selective harmonic elimination (PI-SHE) and the use of multiple switching levels. PI-SHE is shown to enable multiples of any selected harmonic to be eliminated through controlled timing of the transition between different excitation voltage levels. Multiples of the third harmonic are shown to be eliminated in three-level tone waveforms. In addition, multiples of the fifth harmonic are shown to be eliminated using five-level tone waveforms. A method of calculating the expected amplitude of each harmonic is presented. The application of PI-SHE in linear frequency-modulated (LFM) excitation is proposed. A heuristic derivation of the spectral properties of multilevel switched LFM waveforms is presented. The performance of the proposed PI-SHE method is confirmed through experimental measurement of the harmonics present in an ultrasound wave using two, three, and five levels for both tone and LFM excitation. The proposed method of controlling harmonics through the use of multilevel switched excitation is especially suitable for applications in which portability, high channel counts, and precise harmonic control are required.

  18. A Coupled Field Multiphysics Modeling Approach to Investigate RF MEMS Switch Failure Modes under Various Operational Conditions

    PubMed Central

    Sadek, Khaled; Lueke, Jonathan; Moussa, Walied

    2009-01-01

    In this paper, the reliability of capacitive shunt RF MEMS switches have been investigated using three dimensional (3D) coupled multiphysics finite element (FE) analysis. The coupled field analysis involved three consecutive multiphysics interactions. The first interaction is characterized as a two-way sequential electromagnetic (EM)-thermal field coupling. The second interaction represented a one-way sequential thermal-structural field coupling. The third interaction portrayed a two-way sequential structural-electrostatic field coupling. An automated substructuring algorithm was utilized to reduce the computational cost of the complicated coupled multiphysics FE analysis. The results of the substructured FE model with coupled field analysis is shown to be in good agreement with the outcome of previously published experimental and numerical studies. The current numerical results indicate that the pull-in voltage and the buckling temperature of the RF switch are functions of the microfabrication residual stress state, the switch operational frequency and the surrounding packaging temperature. Furthermore, the current results point out that by introducing proper mechanical approaches such as corrugated switches and through-holes in the switch membrane, it is possible to achieve reliable pull-in voltages, at various operating temperatures. The performed analysis also shows that by controlling the mean and gradient residual stresses, generated during microfabrication, in conjunction with the proposed mechanical approaches, the power handling capability of RF MEMS switches can be increased, at a wide range of operational frequencies. These design features of RF MEMS switches are of particular importance in applications where a high RF power (frequencies above 10 GHz) and large temperature variations are expected, such as in satellites and airplane condition monitoring. PMID:22408490

  19. Robust pre-specified time synchronization of chaotic systems by employing time-varying switching surfaces in the sliding mode control scheme

    NASA Astrophysics Data System (ADS)

    Khanzadeh, Alireza; Pourgholi, Mahdi

    2016-08-01

    In the conventional chaos synchronization methods, the time at which two chaotic systems are synchronized, is usually unknown and depends on initial conditions. In this work based on Lyapunov stability theory a sliding mode controller with time-varying switching surfaces is proposed to achieve chaos synchronization at a pre-specified time for the first time. The proposed controller is able to synchronize chaotic systems precisely at any time when we want. Moreover, by choosing the time-varying switching surfaces in a way that the reaching phase is eliminated, the synchronization becomes robust to uncertainties and exogenous disturbances. Simulation results are presented to show the effectiveness of the proposed method of stabilizing and synchronizing chaotic systems with complete robustness to uncertainty and disturbances exactly at a pre-specified time.

  20. Self-organization of the Q-switched mode-locked regime in a diode-pumped Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Donin, V. I.; Yakovin, D. V.; Gribanov, A. V.

    2015-06-01

    A new Q-switched mode-locked generation regime of a solid-state laser, in which a Q-switch is "spontaneously" formed at the frequency of relaxation oscillations, has been observed for the first time. The new generation has been implemented by means of the previously proposed method of an acoustic modulator of a traveling wave in combination with a spherical mirror of a cavity. Stable pulse trains with a repetition frequency of ~30 kHz and a duration of ~2 µs have been observed in the diode-pump Nd:YAG laser with an average output power of ~3 W. Each train contains about 200 equispaced single pulses with a duration of ~45 ps.

  1. Stable Q-switched and mode-locked Nd:GdVO4/KTP green laser with dual-loss-modulation.

    PubMed

    Zhang, Gang; Zhao, Shengzhi; Li, Guiqiu; Li, Dechun; Yang, Kejian; Cheng, Kang; Zhang, Yan

    2010-08-20

    A diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:GdVO(4)/KTP green laser with an acousto-optic modulator (AOM) and GaAs saturable absorber is presented. The experimental results show that the stability and the peak power of the dual-loss-modulated QML Nd:GdVO(4)/KTP green laser are significantly improved. The pulse width of the Q-switched pulse envelope in the dual-loss-modulation QML green laser has a compression of 50% compared with that in the singly passively QML green laser with GaAs. By using a hyperbolic secant square function and considering the Gaussian distribution of the intracavity photon density, the coupled equations for diode-pumped dual-loss-modulated QML Nd:GdVO(4) green laser are given, and the numerical solutions of the equations are in good agreement with the experimental results.

  2. Design, Modeling, and Fabrication of Chemical Vapor Deposition Grown MoS2 Circuits with E-Mode FETs for Large-Area Electronics.

    PubMed

    Yu, Lili; El-Damak, Dina; Radhakrishna, Ujwal; Ling, Xi; Zubair, Ahmad; Lin, Yuxuan; Zhang, Yuhao; Chuang, Meng-Hsi; Lee, Yi-Hsien; Antoniadis, Dimitri; Kong, Jing; Chandrakasan, Anantha; Palacios, Tomas

    2016-10-12

    Two-dimensional electronics based on single-layer (SL) MoS2 offers significant advantages for realizing large-scale flexible systems owing to its ultrathin nature, good transport properties, and stable crystalline structure. In this work, we utilize a gate first process technology for the fabrication of highly uniform enhancement mode FETs with large mobility and excellent subthreshold swing. To enable large-scale MoS2 circuit, we also develop Verilog-A compact models that accurately predict the performance of the fabricated MoS2 FETs as well as a parametrized layout cell for the FET to facilitate the design and layout process using computer-aided design (CAD) tools. Using this CAD flow, we designed combinational logic gates and sequential circuits (AND, OR, NAND, NOR, XNOR, latch, edge-triggered register) as well as switched capacitor dc-dc converter, which were then fabricated using the proposed flow showing excellent performance. The fabricated integrated circuits constitute the basis of a standard cell digital library that is crucial for electronic circuit design using hardware description languages. The proposed design flow provides a platform for the co-optimization of the device fabrication technology and circuits design for future ubiquitous flexible and transparent electronics using two-dimensional materials.

  3. All-fiber dual-wavelength Q-switched and mode-locked EDFL by SMF-THDF-SMF structure as a saturable absorber

    NASA Astrophysics Data System (ADS)

    Latiff, A. A.; Kadir, N. A.; Ismail, E. I.; Shamsuddin, H.; Ahmad, H.; Harun, S. W.

    2017-04-01

    We demonstrate all-fiber dual-wavelength Q-switched and mode-locked erbium-doped fiber laser (EDFL) by utilizing the thulium-holmium-doped fiber (THDF) as a fiber saturable absorber (SA) and also a Mach-Zehnder interferometer (MZI) element. The 19 cm long THDF has a core diameter of 11.5 μm, refractive index difference of 0.005, and cutoff wavelength of 1810 nm. Stable dual-wavelength Q-switching operation was generated at 1555.14 nm and 1557.64 nm with free spectral range (FSR) of 2.5 nm. The repetition rate of 14.45-78.49 kHz was obtained between 12 and 100 mW pump power. At maximum pump power, the maximum output power and pulse energy were 2.58 mW and 32.87 nJ, respectively. By adding 195 cm long SMF in the same cavity, the stable dual-wavelength mode-locking operation was started at 166 mW and continue stable to 201 mW pump power. This mode-locking operation produced stable dual-wavelength pulses at 1530.34 nm and 1532.84 nm with a repetition rate of 1 MHz with a pulse duration of 128 ns and signal-to-noise ratio (SNR) of 62 dB. It shares the same value of FSR in Q-switching operation. The highest output power of 1.57 nJ corresponds to the maximum output power of 1.57 mW was obtained. Our results validate the linear absorption characteristic at C-band region and multimode fiber effect of THDF can be utilized as SA to generate stable all-fiber dual-wavelength pulsed lasers. Remarkably, these findings expand a fiber gain medium application in short pulse generation.

  4. Quality engineering tools focused on high power LED driver design using boost power stages in switch mode

    NASA Astrophysics Data System (ADS)

    Ileana, Ioan; Risteiu, Mircea; Marc, Gheorghe

    2016-12-01

    This paper is a part of our research dedicated to high power LED lamps designing. The boost-up selected technology wants to meet driver producers' tendency in the frame of efficiency and disturbances constrains. In our work we used modeling and simulation tools for implementing scenarios of the driver work when some controlling functions are executed (output voltage/ current versus input voltage and fixed switching frequency, input and output electric power transfer versus switching frequency, transient inductor voltage analysis, and transient out capacitor analysis). Some electrical and thermal stress conditions are also analyzed. Based on these aspects, a high reliable power LED driver has been designed.

  5. Passively Q-switched and mode-locked Nd:GGG laser with a Bi-doped GaAs saturable absorber.

    PubMed

    Cong, Wen; Li, Dechun; Zhao, Shengzhi; Yang, Kejian; Li, Xiangyang; Qiao, Hui; Liu, Ji

    2014-06-16

    A simultaneously passively Q-switched and mode-locked (QML) Nd:GGG laser using a Bi-doped GaAs wafer as saturable absorber is accomplished for the first time. The Bi-doped GaAs wafer is fabricated by ion implantation and subsequent annealing. In comparison to the passively QML laser with GaAs, the QML laser with Bi-doped GaAs can generate more stable pulses with 99% modulation depth. The experiment results indicate that the Bi-doped GaAs could be an excellent saturable absorber for diode-pumped QML lasers.

  6. Switching phase separation mode by varying the hydrophobicity of polymer additives in solution-processed semiconducting small-molecule/polymer blends

    NASA Astrophysics Data System (ADS)

    He, Zhengran; Li, Dawen; Hensley, Dale K.; Rondinone, Adam J.; Chen, Jihua

    2013-09-01

    Lateral and vertical phase separations play critical roles in the performance of the next-generation organic and hybrid electronic devices. A method is demonstrated here to switch between lateral and vertical phase separations in semiconducting 6,13-bis(triisopropylsilylethynyl) pentacene (TIPSE pentacene)/polymer blend films by simply varying the alkyl length of the polyacrylate polymer component. The phase separation modes depend on intermolecular interactions between small molecule TIPSE pentancene and polymer additives. The blend film with a dominant vertical phase separation exhibits a significant enhancement in average mobility and performance consistency of organic thin-film transistors.

  7. Numerical simulation of dual-loss-modulated Q-switched and mode-locked laser with an acousto-optic and Cr4+:YAG saturable absorber.

    PubMed

    Zhao, Shengzhi; Li, Guiqiu; Li, Dechun; Yang, Kejian; Li, Yufei; Li, Ming; Li, Tao; Zhang, Gang; Cheng, Kang

    2010-04-01

    By considering the influence of the turn-off time and the modulation frequency of the acousto-optic (AO) modulator as well as the Gaussian spatial distribution of the photon density, we give a developed rate equation model for a diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:GdVO(4) laser with AO modulator and Cr(4+):YAG saturable absorber. With this developed model, the dual-loss-modulated QML laser characteristics, such as pulse width and pulse energy, can be numerically simulated, and the theoretical evaluations are in good agreement with the experimental results.

  8. Q-Switched and Mode Locked Short Pulses from a Diode Pumped, YB-Doped Fiber Laser

    DTIC Science & Technology

    2009-03-26

    SESAM ) and through nonlinear polarization rotation (NPR). Output power and spectra were measured in cw after testing two different Yb- fibers and...17.2 MHz. Mode locking was not achieved using the SESAM , but the results that resemble mode beating are presented, and causes for error are analyzed...20 2.5.1 Mode Locking with a Semiconductor Saturable Absorber Mirror ( SESAM ) ..21 2.5.2 Nonlinear Polarization Rotation

  9. Numerical modeling of the phase-conjugate laser with an intra-cavity stimulated Brillouin scattering mirror: Q-switching mode

    NASA Astrophysics Data System (ADS)

    Yashkir, Yuri

    2006-04-01

    We present a new computer numerical model of the phase-conjugate laser, utilizing an intra-cavity Stimulated Brillouin Scattering (SBS) element. The modelled laser system includes the active laser crystal which is placed between the output coupler mirror and a stimulated Brillouin scattering cell. The numerical model includes a set of rate equations for the active crystal inverse population, and for the photon density inside the laser cavity. The SBS backscattering model is based on a reduced set of coupled equations for electromagnetic fields for two waves (a pump wave and an SBS wave) propagating in opposite directions. The numerical integration of the set of equations simulates in detail the temporal dynamics of the laser. A wide range of realistic system parameters was numerically investigated. Different laser regimes (from a quasi -CW mode to a Q-switched mode) were numerically tested. The method of numerical modelling of such laser system can be efficiently used for an optimal laser design.

  10. Passively Q-switched mode-locking Erbium-doped fiber laser with net-normal dispersion using nonlinear polarization rotation technique

    NASA Astrophysics Data System (ADS)

    Wang, L. Y.; Xu, W. C.; Luo, Z. C.; Cao, W. J.; Luo, A. P.; Dong, J. L.; Wang, H. Y.

    2011-10-01

    We experimentally demonstrate a passively Q-switched mode-locking (QML) operation in an Erbium-doped fiber ring laser with net normal dispersion by using nonlinear polarization rotation technique. A 2 m long section of dispersion compensating fiber (DCF) with extra large positive dispersion was inserted into the cavity to ensure the fiber laser working in the region of net positive dispersion. By carefully adjusting the polarization controller, both uniform dissipative mode-locking pulses with fundamental repetition rate and QML pulse trains with tunable repetition rate from 71.58 to 98.83 kHz are achieved. It is found that the QML operation is caused by the interaction between the polarization state of the pulse and the intracavity polarizer.

  11. Electrooptical and Response/Relaxation Properties of Liquid Crystal Cells in In-plane Switching Mode with Polyvinylcinnamate Photoinduced Alignment Layer

    NASA Astrophysics Data System (ADS)

    Zhou, Ying; Sato, Susumu

    1998-08-01

    Using polyvinylcinnamate (PVCi) photoinduced alignment layers and rubbed polyvinylalcohol (PVA) alignment layers, we produced PVCi-PVA and PVA-PVA in-plane switching (IPS) cells. Transmission properties of the two kinds of IPS-mode cells show that it is possible to decrease the driving voltage for the IPS-mode cell with a weak anchoring alignment surface. The response times of the PVCi-PVA cells are almost the same as those of the PVA-PVA cells, however, the measurement results of the relaxation times for the PVCi-PVA cells indicate that they depend on the time of the voltage applied, and the relaxation times increase with the increase of the applying time. Furthermore, we investigate the decline effect of the twist angle of a PVCi-PVA cell with time after a voltage has been applied for a very long time and then removed.

  12. Mode switching in a multi-wavelength distributed feedback quantum cascade laser using an external micro-cavity

    SciTech Connect

    Sidler, Meinrad; Rauter, Patrick; Blanchard, Romain; Métivier, Pauline; Capasso, Federico; Mansuripur, Tobias S.; Wang, Christine; Huang, Yong; Ryou, Jae-Hyun; Dupuis, Russell D.; Faist, Jérôme

    2014-02-03

    We demonstrate a multi-wavelength distributed feedback (DFB) quantum cascade laser (QCL) operating in a lensless external micro-cavity and achieve switchable single-mode emission at three distinct wavelengths selected by the DFB grating, each with a side-mode suppression ratio larger than 30 dB. Discrete wavelength tuning is achieved by modulating the feedback experienced by each mode of the multi-wavelength DFB QCL, resulting from a variation of the external cavity length. This method also provides a post-fabrication control of the lasing modes to correct for fabrication inhomogeneities, in particular, related to the cleaved facets position.

  13. Should I Stay or Should I Switch? An Analysis of Transitions between Modes of Vocational Education and Training

    ERIC Educational Resources Information Center

    Latina, Joelle

    2017-01-01

    How established is the horizontal permeability between modes of vocational education and training (VET) in Switzerland? Formally encouraged by the Swiss law on VET, horizontal permeability refers to transitions across VET modes, i.e. between dual and school-based VET. This paper first discusses why horizontal permeability is indeed relevant and…

  14. Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber

    PubMed Central

    Jia, Chenglai; Shastri, Bhavin J.; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R.; Saad, Mohammed; Chen, Lawrence R.

    2016-01-01

    Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm3+:ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications. PMID:27804993

  15. Quantum dot cadmium selenide as a saturable absorber for Q-switched and mode-locked double-clad ytterbium-doped fiber lasers

    NASA Astrophysics Data System (ADS)

    Mahyuddin, M. B. H.; Latiff, A. A.; Rusdi, M. F. M.; Irawati, N.; Harun, S. W.

    2017-08-01

    This paper demonstrates the integration of quantum dot (QD) cadmium selenide (CdSe) nanoparticles, which is embedded into polymethyl methacrylate (PMMA) film into an ytterbium-doped fiber laser (YDFL) cavity to produce Q-switched and mode-locked fiber lasers. The QD CdSe based film functions as a saturable absorber (SA). For Q-switching operation, stable pulse is generated within 970-1200 mW pump power, with tunable repetition rate and pulse width of 24.5-40.5 kHz and 6.8-3.7 μs, respectively. Maximum pulse energy and peak power are obtained about 1.1 μJ and 0.28 W, respectively. As we tune the polarization state of the laser cavity and use a single QD CdSe film, the mode-locking operation could also be generated within 310-468 mW pump power with repetition rate of 14.5 MHz and pulse width of 3.5 ps. Maximum pulse energy and peak power are obtained about 2 nJ and 0.11 W, respectively. These results may contribute to continuous research work on laser pulse generation, providing new opportunities of CdSe material in photonics applications.

  16. Passively synchronized Q-switched and mode-locked dual-band Tm(3+):ZBLAN fiber lasers using a common graphene saturable absorber.

    PubMed

    Jia, Chenglai; Shastri, Bhavin J; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R; Saad, Mohammed; Chen, Lawrence R

    2016-11-02

    Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm(3+):ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

  17. Optical Switching Using Transition from Dipolar to Charge Transfer Plasmon Modes in Ge2Sb2Te5 Bridged Metallodielectric Dimers

    NASA Astrophysics Data System (ADS)

    Ahmadivand, Arash; Gerislioglu, Burak; Sinha, Raju; Karabiyik, Mustafa; Pala, Nezih

    2017-02-01

    Capacitive coupling and direct shuttling of charges in nanoscale plasmonic components across a dielectric spacer and through a conductive junction lead to excitation of significantly different dipolar and charge transfer plasmon (CTP) resonances, respectively. Here, we demonstrate the excitation of dipolar and CTP resonant modes in metallic nanodimers bridged by phase-change material (PCM) sections, material and electrical characteristics of which can be controlled by external stimuli. Ultrafast switching (in the range of a few nanoseconds) between amorphous and crystalline phases of the PCM section (here Ge2Sb2Te5 (GST)) allows for designing a tunable plasmonic switch for optical communication applications with significant modulation depth (up to 88%). Judiciously selecting the geometrical parameters and taking advantage of the electrical properties of the amorphous phase of the GST section we adjusted the extinction peak of the dipolar mode at the telecommunication band (λ~1.55 μm), which is considered as the OFF state. Changing the GST phase to crystalline via optical heating allows for direct transfer of charges through the junction between nanodisks and formation of a distinct CTP peak at longer wavelengths (λ~1.85 μm) far from the telecommunication wavelength, which constitutes the ON state.

  18. Optical Switching Using Transition from Dipolar to Charge Transfer Plasmon Modes in Ge2Sb2Te5 Bridged Metallodielectric Dimers

    PubMed Central

    Ahmadivand, Arash; Gerislioglu, Burak; Sinha, Raju; Karabiyik, Mustafa; Pala, Nezih

    2017-01-01

    Capacitive coupling and direct shuttling of charges in nanoscale plasmonic components across a dielectric spacer and through a conductive junction lead to excitation of significantly different dipolar and charge transfer plasmon (CTP) resonances, respectively. Here, we demonstrate the excitation of dipolar and CTP resonant modes in metallic nanodimers bridged by phase-change material (PCM) sections, material and electrical characteristics of which can be controlled by external stimuli. Ultrafast switching (in the range of a few nanoseconds) between amorphous and crystalline phases of the PCM section (here Ge2Sb2Te5 (GST)) allows for designing a tunable plasmonic switch for optical communication applications with significant modulation depth (up to 88%). Judiciously selecting the geometrical parameters and taking advantage of the electrical properties of the amorphous phase of the GST section we adjusted the extinction peak of the dipolar mode at the telecommunication band (λ~1.55 μm), which is considered as the OFF state. Changing the GST phase to crystalline via optical heating allows for direct transfer of charges through the junction between nanodisks and formation of a distinct CTP peak at longer wavelengths (λ~1.85 μm) far from the telecommunication wavelength, which constitutes the ON state. PMID:28205643

  19. Optical Switching Using Transition from Dipolar to Charge Transfer Plasmon Modes in Ge2Sb2Te5 Bridged Metallodielectric Dimers.

    PubMed

    Ahmadivand, Arash; Gerislioglu, Burak; Sinha, Raju; Karabiyik, Mustafa; Pala, Nezih

    2017-02-16

    Capacitive coupling and direct shuttling of charges in nanoscale plasmonic components across a dielectric spacer and through a conductive junction lead to excitation of significantly different dipolar and charge transfer plasmon (CTP) resonances, respectively. Here, we demonstrate the excitation of dipolar and CTP resonant modes in metallic nanodimers bridged by phase-change material (PCM) sections, material and electrical characteristics of which can be controlled by external stimuli. Ultrafast switching (in the range of a few nanoseconds) between amorphous and crystalline phases of the PCM section (here Ge2Sb2Te5 (GST)) allows for designing a tunable plasmonic switch for optical communication applications with significant modulation depth (up to 88%). Judiciously selecting the geometrical parameters and taking advantage of the electrical properties of the amorphous phase of the GST section we adjusted the extinction peak of the dipolar mode at the telecommunication band (λ~1.55 μm), which is considered as the OFF state. Changing the GST phase to crystalline via optical heating allows for direct transfer of charges through the junction between nanodisks and formation of a distinct CTP peak at longer wavelengths (λ~1.85 μm) far from the telecommunication wavelength, which constitutes the ON state.

  20. Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber

    NASA Astrophysics Data System (ADS)

    Jia, Chenglai; Shastri, Bhavin J.; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R.; Saad, Mohammed; Chen, Lawrence R.

    2016-11-01

    Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm3+:ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

  1. A possible role of oxidative stress in the switch mechanism of the cell death mode from apoptosis to necrosis--studies on rho0 cells.

    PubMed

    Wochna, Agnieszka; Niemczyk, Edyta; Kurono, Chieko; Masaoka, Makoto; Kedzior, Jakub; Słomińska, Ewa; Lipiński, Marcin; Wakabayashi, Takashi

    2007-01-01

    Apoptosis is induced not only during morphogenesis and embryogenesis but also under various pathological conditions, especially related to oxidative stress. Apoptotic cells are phagocytized by neighboring cells while necrotic cells cause local and general reactions sometimes lethal to our bodies. Data have been accumulated to demonstrate that the switch of the cell death mode from apoptosis to necrosis does occur. However, detailed mechanisms involved in the switch mechanism remain unsolved although decreases in the intracellular level of ATP and a burst in the cellular level of reactive oxygen species (ROS) have been proposed. Recently, we have shown that the population of apoptotic cells reaches maximum in human osteosarcoma 143B cells treated for 6h with menadione (MEN) while necrotic cells become predominant at 9h of the treatment. In the present study we have attempted to clarify the role of cellular ATP in the switch mechanism using rho(0) cells derived from human osteosarcoma rho+ cells. Results are summarized as follows: (1) Apoptotic and necrotic changes in rho(0) cells are much faster than rho+ cells after the treatment with MEN. (2) Cellular level of ATP in rho(0) cells remains essentially in the same level before and after the MEN-treatment while intracellular levels of superoxide continuously increase after the MEN-treatment. (3) rho+ cells treated with MEN in the presence of antimycin A plus oligomycin show similar changes to those of MEN-treated rho(0) cells. (4) MEN-induced increases in the cellular level of superoxide are distinctly suppressed by inhibitors of NADPH oxidase. These results suggest that the intracellular level of superoxide may be a key factor directly related to the switch mechanism from apoptosis to necrosis, and that decreases in cellular level of ATP accelerate both apoptotic and necrotic changes of the cells.

  2. Exploring the self-mode-locked dynamics of cryogenic diode-pumped Nd:YLF lasers: switching of orthogonal polarizations

    NASA Astrophysics Data System (ADS)

    Huang, T. L.; Y Cho, C.; Liang, H. C.; Huang, K. F.; Chen, Y. F.

    2017-08-01

    The self-mode-locked output for cryogenic Nd:YLF laser at the temperature range of 90 K to 290 K is thoroughly investigated. Linearly polarized self-mode-locked lasing at 1047 nm (1053 nm) with a repetition rate up to 1.59 GHz and a pulse width as short as 52 ps can be realized at temperatures above 155 K (below 135 K). Orthogonally polarized self-mode-locked operation can be observed at temperatures near 145 K. During dual-polarization operation, it is found that the polarized component with higher output power is the fundamental transverse mode, whereas the other component with lower output power becomes the high-order transverse mode. The dominant polarized component can be either π- or σ-polarization, depending on the fine adjustment of the cavity.

  3. Allosteric communication pathways routed by Ca2+/Mg2+ exchange in GCAP1 selectively switch target regulation modes

    PubMed Central

    Marino, Valerio; Dell’Orco, Daniele

    2016-01-01

    GCAP1 is a neuronal calcium sensor protein that regulates the phototransduction cascade in vertebrates by switching between activator and inhibitor of the target guanylate cyclase (GC) in a Ca2+-dependent manner. We carried out exhaustive molecular dynamics simulations of GCAP1 and determined the intramolecular communication pathways involved in the specific GC activator/inhibitor switch. The switch was found to depend on the Mg2+/Ca2+ loading states of the three EF hands and on the way the information is transferred from each EF hand to specific residues at the GCAP1/GC interface. Post-translational myristoylation is fundamental to mediate long range allosteric interactions including the EF2-EF4 coupling and the communication between EF4 and the GC binding interface. Some hubs in the identified protein network are the target of retinal dystrophy mutations, suggesting that the lack of complete inhibition of GC observed in many cases is likely due to the perturbation of intra/intermolecular communication routes. PMID:27739433

  4. A crossbar resistance switching memory readout scheme with sneak current cancellation based on a two-port current-mode sensing

    NASA Astrophysics Data System (ADS)

    Bae, Woorham; Yoon, Kyung Jean; Hwang, Cheol Seong; Jeong, Deog-Kyoon

    2016-12-01

    This paper describes a novel readout scheme that enables the complete cancellation of sneak currents in resistive switching random-access memory (RRAM) crossbar array. The current-mode readout is employed in the proposed readout, and a few critical advantages of the current-mode readout for crossbar RRAM are elucidated in this paper. The proposed scheme is based on a floating readout scheme for low power consumption, and one more sensing port is introduced using an additional reference word line. From the additional port, information on the sneak current amount is collected, and simple current-mode arithmetic operations are implemented to cancel out the sneak current from the sensing current. In addition, a simple method of handling the overestimated-sneak-current issue is described. The proposed scheme is verified using HSPICE simulation. Moreover, an example of a current-mode sense amplifier realizing the proposed cancelling technique is presented. The proposed sense amplifier can be implemented with less hardware overhead compared to the previous works.

  5. A crossbar resistance switching memory readout scheme with sneak current cancellation based on a two-port current-mode sensing.

    PubMed

    Bae, Woorham; Yoon, Kyung Jean; Hwang, Cheol Seong; Jeong, Deog-Kyoon

    2016-12-02

    This paper describes a novel readout scheme that enables the complete cancellation of sneak currents in resistive switching random-access memory (RRAM) crossbar array. The current-mode readout is employed in the proposed readout, and a few critical advantages of the current-mode readout for crossbar RRAM are elucidated in this paper. The proposed scheme is based on a floating readout scheme for low power consumption, and one more sensing port is introduced using an additional reference word line. From the additional port, information on the sneak current amount is collected, and simple current-mode arithmetic operations are implemented to cancel out the sneak current from the sensing current. In addition, a simple method of handling the overestimated-sneak-current issue is described. The proposed scheme is verified using HSPICE simulation. Moreover, an example of a current-mode sense amplifier realizing the proposed cancelling technique is presented. The proposed sense amplifier can be implemented with less hardware overhead compared to the previous works.

  6. E-beam high voltage switching power supply

    DOEpatents

    Shimer, Daniel W.; Lange, Arnold C.

    1996-01-01

    A high-power power supply produces a controllable, constant high voltage put under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules.

  7. E-beam high voltage switching power supply

    DOEpatents

    Shimer, D.W.; Lange, A.C.

    1996-10-15

    A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules. 5 figs.

  8. Reversible switching of quantum cascade laser-modes using a pH-responsive polymeric cladding as transducer.

    PubMed

    Basnar, Bernhard; Schartner, Stephan; Austerer, Maximilian; Andrews, Aaron Maxwell; Roch, Tomas; Schrenk, Werner; Strasser, Gottfried

    2008-06-09

    We present a novel approach for the reversible switching of the emission wavelength of a quantum cascade laser (QCL) using a halochromic cladding. An air-waveguide laser ridge is coated with a thin layer of polyacrylic acid. This cladding introduces losses corresponding to the absorption spectrum of the polymer. By changing the state of the polymer, the absorption spectrum and losses change, inducing a shift of 7 cm(-1) in the emission wavelength. This change is induced by exposure to acidic or alkaline vapors under ambient conditions and is fully reversible. Such lasers can be used as multi-color light source and as sensor for atmospheric pH.

  9. Highly efficient, versatile, self-Q-switched, high-repetition-rate microchip laser generating Ince-Gaussian modes for optical trapping

    NASA Astrophysics Data System (ADS)

    Dong, Jun; He, Yu; Zhou, Xiao; Bai, Shengchuang

    2016-03-01

    Lasers operating in the Ince-Gaussian (IG) mode have potential applications for optical manipulation of microparticles and formation of optical vortices, as well as for optical trapping and optical tweezers. Versatile, self-Q-switched, high-peak-power, high-repetition-rate Cr, Nd:YAG microchip lasers operating in the IG mode are implemented under tilted, tightly focused laser-diode pumping. An average output power of over 2 W is obtained at an absorbed pump power of 6.4 W. The highest optical-to-optical efficiency of 33.2% is achieved at an absorbed pump power of 3.9 W. Laser pulses with a pulse energy of 7.5 μJ, pulse width of 3.5 ns and peak power of over 2 kW are obtained. A repetition rate up to 335 kHz is reached at an absorbed pump power of 5.8 W. Highly efficient, versatile, IG-mode lasers with a high repetition rate and a high peak power ensure a better flexibility in particle manipulation and optical trapping.

  10. Highly efficient, versatile, self-Q-switched, high-repetition-rate microchip laser generating Ince–Gaussian modes for optical trapping

    SciTech Connect

    Jun Dong; Yu He; Xiao Zhou; Shengchuang Bai

    2016-03-31

    Lasers operating in the Ince-Gaussian (IG) mode have potential applications for optical manipulation of microparticles and formation of optical vortices, as well as for optical trapping and optical tweezers. Versatile, self-Q-switched, high-peak-power, high-repetition-rate Cr, Nd:YAG microchip lasers operating in the IG mode are implemented under tilted, tightly focused laser-diode pumping. An average output power of over 2 W is obtained at an absorbed pump power of 6.4 W. The highest optical-to-optical efficiency of 33.2% is achieved at an absorbed pump power of 3.9 W. Laser pulses with a pulse energy of 7.5 μJ, pulse width of 3.5 ns and peak power of over 2 kW are obtained. A repetition rate up to 335 kHz is reached at an absorbed pump power of 5.8 W. Highly efficient, versatile, IG-mode lasers with a high repetition rate and a high peak power ensure a better flexibility in particle manipulation and optical trapping. (control of laser radiation parameters)

  11. Improved Transient and Steady-State Performances of Series Resonant ZCS High-Frequency Inverter-Coupled Voltage Multiplier Converter with Dual Mode PFM Control Scheme

    NASA Astrophysics Data System (ADS)

    Chu, Enhui; Gamage, Laknath; Ishitobi, Manabu; Hiraki, Eiji; Nakaoka, Mutsuo

    The A variety of switched-mode high voltage DC power supplies using voltage-fed type or current-fed type high-frequency transformer resonant inverters using MOS gate bipolar power transistors; IGBTs have been recently developed so far for a medical-use X-ray high power generator. In general, the high voltage high power X-ray generator using voltage-fed high frequency inverter with a high voltage transformer link has to meet some performances such as (i) short rising period in start transient of X-ray tube voltage (ii) no overshoot transient response in tube voltage, (iii) minimized voltage ripple in periodic steady-state under extremely wide load variations and filament heater current fluctuation conditions of the X-ray tube. This paper presents two lossless inductor snubber-assisted series resonant zero current soft switching high-frequency inverter using a diode-capacitor ladder type voltage multiplier called Cockcroft-Walton circuit, which is effectively implemented for a high DC voltage X-ray power generator. This DC high voltage generator which incorporates pulse frequency modulated series resonant inverter using IGBT power module packages is based on the operation principle of zero current soft switching commutation scheme under discontinuous resonant current and continuous resonant current transition modes. This series capacitor compensated for transformer resonant power converter with a high frequency transformer linked voltage boost multiplier can efficiently work a novel selectively-changed dual mode PFM control scheme in order to improve the start transient and steady-state response characteristics and can completely achieve stable zero current soft switching commutation tube filament current dependent for wide load parameter setting values with the aid of two lossless inductor snubbers. It is proved on the basis of simulation and experimental results in which a simple and low cost control implementation based on selectively-changed dual-mode PFM for

  12. Developing Seeds of Ricinus communis L., When Detached and Maintained in an Atmosphere of High Relative Humidity, Switch to a Germinative Mode without the Requirement for Complete Desiccation.

    PubMed

    Kermode, A R; Bewley, J D

    1989-06-01

    Immature seeds of castor bean (Ricinus communis) removed from the capsule at 25 to 40 days after pollination (25-40 DAP) and placed in an atmosphere of high relative humidity undergo limited water loss, and germinate upon subsequent return to full hydration. This switch from a developmental to a germinative/growth mode at 40 DAP is reflected in a change in the types of proteins being synthesized in the endosperm; after partial drying, developmental protein synthesis ceases and germinative/growth-related proteins are produced. The nature and timing of these protein synthetic changes elicited upon imbibition are identical to those following premature desiccation/rehydration of 30 and 40 DAP seeds and upon imbibition of the mature dry seed. Enzymes involved in postgerminative reserve mobilization (l-leucyl-beta-naphthylamidase and isocitrate lyase) are induced upon imbibition, following partial drying at 40 DAP, to levels attained in the endosperms of germinated mature, and prematurely dried/rehydrated, seeds. The changes in protein synthesis resulting from partial drying are effected at the transcriptional and post-transcriptional level. Upon return to full hydration some new (i.e. germination and growth-related) mRNAs are synthesized, while others (associated with development) present in the partially dried endosperm decline. Thus developing seeds of castor bean do not have to experience substantial (whole seed) water loss to acquire the ability to germinate and grow upon subsequent imbibition. Seed detachment from the mother plant alone is not sufficient to elicit a switch to germination and growth processes. However, the length of time of detachment from the mother plant, in combination with some water loss may interact to elicit the "switch" from development to germination.

  13. Experimental and theoretical study on an intracavity KTiOPO4 optical parametric oscillator pumped by a dual loss modulated Q-switched and mode-locked laser

    NASA Astrophysics Data System (ADS)

    Qiao, Junpeng; Zhao, Shengzhi; Yang, Kejian; Zhao, Jia; Li, Guiqiu; Li, Dechun; Li, Tao; Qiao, Wenchao; Chu, Hongwei; Luan, Chao

    2017-07-01

    In this paper, a sub-nanosecond KTiOPO4 (KTP)-based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss modulated Q-switched and mode-locked (QML) laser with an acousto-optic modulator (AOM) and a Cr4+:YAG saturable absorber (Cr4+:YAG-SA) has been demonstrated. By changing the initial transmission of Cr4+:YAG-SA and the transmission of the output coupler at the signal wavelength, the signal pulse width compression can be realized. At an incident pump power of 8.3 W and an AOM repetition rate of 15 kHz, a single signal pulse underneath Q-switched envelope with the shortest pulse width of 220 ps was obtained. The experimental results reveal that this is a simple and effective way to obtain the sub-nanosecond OPO signal pulses. In addition, the related coupled rate equations have been set up and the simulation results agreed with the experimental results well.

  14. Modeling and simulation of enhancement mode p-GaN Gate AlGaN/GaN HEMT for RF circuit switch applications

    NASA Astrophysics Data System (ADS)

    Panda, D. K.; Lenka, T. R.

    2017-06-01

    An enhancement mode p-GaN gate AlGaN/GaN HEMT is proposed and a physics based virtual source charge model with Landauer approach for electron transport has been developed using Verilog-A and simulated using Cadence Spectre, in order to predict device characteristics such as threshold voltage, drain current and gate capacitance. The drain current model incorporates important physical effects such as velocity saturation, short channel effects like DIBL (drain induced barrier lowering), channel length modulation (CLM), and mobility degradation due to self-heating. The predicted I d-V ds, I d-V gs, and C-V characteristics show an excellent agreement with the experimental data for both drain current and capacitance which validate the model. The developed model was then utilized to design and simulate a single-pole single-throw (SPST) RF switch.

  15. Black phosphorus: a two-dimension saturable absorption material for mid-infrared Q-switched and mode-locked fiber lasers

    PubMed Central

    Li, Jianfeng; Luo, Hongyu; Zhai, Bo; Lu, Rongguo; Guo, Zhinan; Zhang, Han; Liu, Yong

    2016-01-01

    Black phosphorus (BP) as a novel class of two-dimension (2D) materials has recently attracted enormous attention as a result of its unique physical and chemical features. The remarkably strong light-matter interaction and tunable direct band-gap at a wide range make it an ideal candidate especially in the mid-infrared wavelength region as the saturable absorber (SA). In this paper, the simple and effective liquid phase exfoliation (LPE) method was used to fabricate BP. By introducing the same BP SA into two specifically designed rare earth ions doped fluoride fiber lasers at mid-infrared wavebands, Q-switching with the pulse energy of 4.93 μJ and mode-locking with the pulse duration of 8.6 ps were obtained, respectively. The operation wavelength of ~2970 nm for generated pulse is the reported longest wavelength for BP SA based fiber lasers. PMID:27457338

  16. Eye-Safe KGd(WO4)2:Nd Laser: Nano- and Subnanosecond Pulse Generation in Self-Frequency Raman Conversion Mode with Active Q-Switching

    NASA Astrophysics Data System (ADS)

    Dashkevich, V. I.; Orlovich, V. A.

    2017-03-01

    The shape of the multimode Stokes pulse generated by an eye-safe KGd(WO4)2:Nd laser with self-frequency Raman conversion and active Q-switching was shown to depend on the inhomogeneity of the active-medium pump. The laser generated a short and undistorted Stokes pulse of length 2.5 ns that increased with increasing laser cavity length for a moderately inhomogeneous pump characterized by a higher population inversion in the center of the active element. The energy of the Stokes pulse ( 11.5 mJ) varied little as the output-mirror reflectivity varied in the range 5-45%. The Raman pulse became distorted if the inhomogeneity of the pump was increased considerably. The degree of pump inhomogeneity was negligible with fundamental TEM00 mode selection. The laser generated subnanosecond Stokes pulses with peak power in the MW range.

  17. Black phosphorus: a two-dimension saturable absorption material for mid-infrared Q-switched and mode-locked fiber lasers.

    PubMed

    Li, Jianfeng; Luo, Hongyu; Zhai, Bo; Lu, Rongguo; Guo, Zhinan; Zhang, Han; Liu, Yong

    2016-07-26

    Black phosphorus (BP) as a novel class of two-dimension (2D) materials has recently attracted enormous attention as a result of its unique physical and chemical features. The remarkably strong light-matter interaction and tunable direct band-gap at a wide range make it an ideal candidate especially in the mid-infrared wavelength region as the saturable absorber (SA). In this paper, the simple and effective liquid phase exfoliation (LPE) method was used to fabricate BP. By introducing the same BP SA into two specifically designed rare earth ions doped fluoride fiber lasers at mid-infrared wavebands, Q-switching with the pulse energy of 4.93 μJ and mode-locking with the pulse duration of 8.6 ps were obtained, respectively. The operation wavelength of ~2970 nm for generated pulse is the reported longest wavelength for BP SA based fiber lasers.

  18. Treatment of congenital melanocytic nevi using the combined (normal-mode plus Q-switched) ruby laser in Asians: clinical response in relation to histological type.

    PubMed

    Kono, Taro; Erçöçen, Ali Rza; Nozaki, Motohiro

    2005-05-01

    Clinical response of congenital melanocytic nevus (CMN) to the combined normal-mode ruby laser (NMRL) and Q-switched ruby laser (QSRL) treatment method (ie, NM plus QS) was correlated with the histologic depth of nevomelanocytic nests to predict the efficacy rate and therapeutic outcome of the laser treatment. Thirty-four patients with CMN were treated using the combined (NM plus QS) ruby laser method. The clinical results of the laser treatment demonstrated that 20 had excellent response, 11 had good response, 3 had fair response, and there was no poor response. When correlated with the histologic type, the efficacy rate of the combined ruby laser was significantly higher in the superficial intradermal type than in the others. We conclude that combining the NMRL and QSRL with appropriate parameters to target both superficial and deep nevomelanocytic components provides a greater degree of penetration of laser light.

  19. Artificial Neural Identification and LMI Transformation for Model Reduction-Based Control of the Buck Switch-Mode Regulator

    NASA Astrophysics Data System (ADS)

    Al-Rabadi, Anas N.

    2009-10-01

    This research introduces a new method of intelligent control for the control of the Buck converter using newly developed small signal model of the pulse width modulation (PWM) switch. The new method uses supervised neural network to estimate certain parameters of the transformed system matrix [Ã]. Then, a numerical algorithm used in robust control called linear matrix inequality (LMI) optimization technique is used to determine the permutation matrix [P] so that a complete system transformation {[B˜], [C˜], [Ẽ]} is possible. The transformed model is then reduced using the method of singular perturbation, and state feedback control is applied to enhance system performance. The experimental results show that the new control methodology simplifies the model in the Buck converter and thus uses a simpler controller that produces the desired system response for performance enhancement.

  20. Tunable diode laser-pumped Tm,Ho:YLF laser operated in continuous-wave and Q-switched modes

    NASA Technical Reports Server (NTRS)

    Mcguckin, B. T.; Hemmati, H.; Menzies, R. T.

    1992-01-01

    Tunable continuous-wave and pulsed laser output was obtained from a Tm-sensitized Ho:YLiF4 crystal at subambient temperatures when longitudinally pumped with a diode laser array. A conversion efficiency of 42 percent and slope efficiency of approximately 60 percent relative to the absorbed pumped power have been achieved at a crystal temperature of 275 K. The emission spectrum was etalon tunable over a range of 16/cm centered at 2067 nm with fine tuning capability of the transition frequency with crystal temperature at measured rate of -0.03/cm/K. Output energies of 0.22 mJ per pulse and 22 ns pulse duration were recorded at Q-switch frequencies that correspond to an effective upper laser level lifetime of 6 ms, and a pulse energy extraction efficiency of 64 percent.

  1. 4.5 W mid-infrared supercontinuum generation in a ZBLAN fiber pumped by a Q-switched mode-locked Tm3+- doped fiber laser

    NASA Astrophysics Data System (ADS)

    Kneis, C.; Donelan, B.; Berrou, A.; Manek-Hönninger, I.; Cadier, B.; Robin, T.; Poulain, M.; Joulain, F.; Eichhorn, M.; Kieleck, C.

    2015-02-01

    The generation of mid-infrared (mid-IR) supercontinuum (SC) radiation, ranging from 2 - 5 μm, is subject of intense research due to its wide range of applications. A very popular host media for mid-IR SC generation are soft glass fibers owing to their low-loss transmission in the mid-IR wavelength regime, particularly fluoride fibers are very attractive for high-power operation. In this research study, a diode-pumped Q-switched mode-locked (QML) thulium (Tm3+)-doped double-clad silica fiber laser is used to pump a ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber for mid-IR SC generation. The QML regime of the fiber laser is actively generated by two acousto-optic modulators. The Tm3+-fiber laser provided up to 23.5 W (26 W) of average output power in QML (continuous wave) regime with a slope efficiency of 36 % (32 %). The measured beam quality has been close to the diffraction-limit in QML regime. The system delivered mode-locked pulses with a duration of 7.5 ps, measured with a commercial autocorrelator system, at a repetition rate of 46 MHz. The Q-switched envelopes had a width between 50 and 150 ns depending on the output power level and the adjustable repetition rate. Mid-IR SC with an average output power in all spectral bands of 4.5 W have been achieved with more than 3 W/ 1.7 W/ 1 W/ 0.36 W after a long-wave-pass filter with a 3 dB-edge at 2.15 μm/ 2.65 μm/ 3.1 μm/ 3.5 μm.

  2. Supercontinuum and four-wave mixing with Q-switched pulses in endlessly single-mode photonic crystal fibres.

    PubMed

    Wadsworth, W; Joly, N; Knight, J; Birks, T; Biancalana, F; Russell, P

    2004-01-26

    Photonic crystal fibres exhibiting endlessly single-mode operation and dispersion zero in the range 1040 to 1100 nm are demonstrated. A sub-ns pump source at 1064 nm generates a parametric output at 732 nm with an efficiency of 35%, or parametric gain of 55 dB at 1315 nm. A broad, flat supercontinuum extending from 500 nm to beyond 1750 nm is also demonstrated using the same pump source.

  3. Avalanche Photoconductive Switching

    DTIC Science & Technology

    1989-06-01

    held off across the switch. In our case this corresponds to 70 kV/cm and is limited by surface flashover . The pulse length is determined by the...off across the gap of the switch, which in turn appears to be limited by surface flashover . There appears to be a threshold electric field of 20-60...and understand this mode of operation. Introduction Laser activated photoconductive switching in semiconductors is a promising technology for high

  4. Thermally actuated thermionic switch

    DOEpatents

    Barrus, Donald M.; Shires, Charles D.

    1988-01-01

    A thermally actuated thermionic switch which responds to an increase of temperature by changing from a high impedance to a low impedance at a predictable temperature set point. The switch has a bistable operation mode switching only on temperature increases. The thermionic material may be a metal which is liquid at the desired operation temperature and held in matrix in a graphite block reservoir, and which changes state (ionizes, for example) so as to be electrically conductive at a desired temperature.

  5. Thermally actuated thermionic switch

    DOEpatents

    Barrus, D.M.; Shires, C.D.

    1982-09-30

    A thermally actuated thermionic switch which responds to an increase of temperature by changing from a high impedance to a low impedance at a predictable temperature set point. The switch has a bistable operation mode switching only on temperature increases. The thermionic material may be a metal which is liquid at the desired operation temperature and held in matrix in a graphite block reservoir, and which changes state (ionizes, for example) so as to be electrically conductive at a desired temperature.

  6. A new ''surface-states'' mode of switching in M-thin insulator-n-p + devices

    NASA Astrophysics Data System (ADS)

    Habib, Serag E.-D.; Eltoukhy, A. A.

    1981-04-01

    The metal-insulator (tunnel) -n-p device (MISS) is known to display current-controlled negative resistance in its I-V characteristics. This negative resistance behavior originates from a positive feedback interaction between the p-n junction and the tunnel metal insulator semiconductor (MIS) parts of the device. The simple structure of the MISS and its amenability to integration has so far been masked by the incomplete understanding of the physics of operation of the device. In this paper, the effect of the surface states at the semiconductor-insulator interface on the MISS behavior is considered. It is shown that the bias dependence of the charge stored in the surface states reduces the switching voltage Vw below the punch-through or avalanche breakdown limits. A simplified model of the MISS is developed taking into account the different roles of the surface states as charge storage centers, recombination centers, and tunnel-current carrying sites. This model is believed to bridge the gap between the previous theoretical models and experimental works.

  7. Phosphoinositides and membrane curvature switch the mode of actin polymerization via selective recruitment of toca-1 and Snx9.

    PubMed

    Gallop, Jennifer L; Walrant, Astrid; Cantley, Lewis C; Kirschner, Marc W

    2013-04-30

    The membrane-cytosol interface is the major locus of control of actin polymerization. At this interface, phosphoinositides act as second messengers to recruit membrane-binding proteins. We show that curved membranes, but not flat ones, can use phosphatidylinositol 3-phosphate [PI(3)P] along with phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] to stimulate actin polymerization. In this case, actin polymerization requires the small GTPase cell cycle division 42 (Cdc42), the nucleation-promoting factor neural Wiskott-Aldrich syndrome protein (N-WASP) and the actin nucleator the actin-related protein (Arp) 2/3 complex. In liposomes containing PI(4,5)P2 as the sole phosphoinositide, actin polymerization requires transducer of Cdc42 activation-1 (toca-1). In the presence of phosphatidylinositol 3-phosphate, polymerization is both more efficient and independent of toca-1. Under these conditions, sorting nexin 9 (Snx9) can be implicated as a specific adaptor that replaces toca-1 to mobilize neural Wiskott-Aldrich syndrome protein and the Arp2/3 complex. This switch in phosphoinositide and adaptor specificity for actin polymerization from membranes has implications for how different types of actin structures are generated at precise times and locations in the cell.

  8. Dual-loss-modulated Q-switched mode-locked laser intracavity pumped temperature-tuned subnanosecond KTiOPO4 optical parametric oscillator.

    PubMed

    Chu, Hongwei; Zhao, Jia; Yang, Kejian; Zhao, Shengzhi; Li, Dechun; Li, Tao; Li, Guiqiu; Qiao, Wenchao

    2015-12-10

    Using an acousto-optic modulator (AOM) and Cr4+:YAG as the dual-loss modulation, an intracavity KTiOPO4 optical parametric oscillator (OPO) pumped by a simultaneously Q-switched and mode-locked (QML) YVO4/Nd:YVO4 laser was realized. The shortest mode-locking pulse duration of the signal wave at 1573 nm was directly measured as 450 ps at an AOM frequency of 2 kHz and a diode pump power of 10.5 W, corresponding to a peak power of 35.5 kW. The temperature tuning of the output signal wavelength was realized in the range from 1571.99 to 1572.61 nm with a blueshift ratio of 0.027  nm/°C. A set of coupled rate equations for the dual-loss-modulated QML laser pumping intracavity OPO was built for the first time to our knowledge. The numerical solutions were fitted with the experimental results.

  9. Simultaneous identification of nine carcinogenic dyes from textiles by liquid chromatography/electrospray ionization mass spectrometry via negative/positive ion switching mode.

    PubMed

    Ding, Youchao; Sun, Cheng; Xu, Xinhua

    2009-01-01

    A method has been established by using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS) for simultaneous separation and identification of nine carcinogenic dyes (Acid Red 26, Direct Blue 6, Direct Black 38, Direct Red 28, Basic Red 9, Basic Violet 14, Disperse Blue 1, Disperse Orange 11 and Disperse Yellow 3) prohibited in textile materials under EU 2002/371/EC decision. Three selected reaction monitoring (SRM) transitions and negative/positive ion switching mode in one single analysis was applied to differentiate between the dyes of different classes. A lower limit of detection was achieved at 0.025-0.25 mg kg(-1) of positive ESI dyes and 0.005-0.025 mg kg(-1) of negative ESI dyes. The accurate and sensitive identification of the nine dissimilar analytes was achieved by combining the characterized ions and retention time of the standards, for example, the characterized ions of [M - xNa](x-), [M -Cl](+) and [M + H](+), respectively were detected for the the sulfonated (acid and direct), basic and disperse dyes. The chromophore groups of azo, triphenylmethane and anthraquinone in precursor ions were found to have fragmented in SRM mode. These results demonstrated a sensitive, accurate and rapid identification.

  10. Intra-cavity frequency doubled Nd:YAG laser with dual-stability-range cavity emitting high power near-diffraction-limited radiation in CW and Q-switched mode

    NASA Astrophysics Data System (ADS)

    Woll, Dirk; Gregg, Jeffrey; Lefort, James; Morehead, James J.; Lindahl, Jennifer

    2010-02-01

    A diode-pumped frequency-doubled Nd:YAG laser has been demonstrated which emits 7.2 W of 532-nm radiation in the CW mode as well as 23 ns, 2.7 mJ pulses at a repetition rate of 10 kHz in the Q-switched mode. The high power in both modes was achieved by intra-cavity second harmonic generation in lithium triborate. The nonlinear output coupling through SHG in this laser causes a factor of 5.7 change of intra-cavity power between the CW and the Q-switched mode. The resulting variation of the thermal lens in the laser rod makes it challenging to maintain a geometrically stable cavity in both operation regimes, which is essential for diffraction limited beam quality. Diffraction limited beam quality with M2 values of less than 1.1 in the CW and less than 1.2 in the Q-switched regime was achieved by a novel dual-stabilityrange cavity-design. This design provides geometrically stable cavity configurations in both operation regimes, which are separated by an unstable region. This cavity makes it possible to switch between the two operation regimes without any moving components.

  11. E-beam high voltage switching power supply

    DOEpatents

    Shimer, D.W.; Lange, A.C.

    1997-03-11

    A high power, solid state power supply is described for producing a controllable, constant high voltage output under varying and arcing loads suitable for powering an electron beam gun or other ion source. The present power supply is most useful for outputs in a range of about 100-400 kW or more. The power supply is comprised of a plurality of discrete switching type dc-dc converter modules, each comprising a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, and an output rectifier for producing a dc voltage at the output of each module. The inputs to the converter modules are fed from a common dc rectifier/filter and are linked together in parallel through decoupling networks to suppress high frequency input interactions. The outputs of the converter modules are linked together in series and connected to the input of the transmission line to the load through a decoupling and line matching network. The dc-dc converter modules are phase activated such that for n modules, each module is activated equally 360{degree}/n out of phase with respect to a successive module. The phased activation of the converter modules, combined with the square current waveforms out of the step up transformers, allows the power supply to operate with greatly reduced output capacitance values which minimizes the stored energy available for discharge into an electron beam gun or the like during arcing. The present power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle using simulated voltage feedback signals and voltage feedback loops. Circuitry is also provided for sensing incipient arc currents reflected at the output of the power supply and for simultaneously decoupling the power supply circuitry from the arcing load. 7 figs.

  12. E-beam high voltage switching power supply

    DOEpatents

    Shimer, Daniel W.; Lange, Arnold C.

    1997-01-01

    A high power, solid state power supply is described for producing a controllable, constant high voltage output under varying and arcing loads suitable for powering an electron beam gun or other ion source. The present power supply is most useful for outputs in a range of about 100-400 kW or more. The power supply is comprised of a plurality of discrete switching type dc-dc converter modules, each comprising a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, and an output rectifier for producing a dc voltage at the output of each module. The inputs to the converter modules are fed from a common dc rectifier/filter and are linked together in parallel through decoupling networks to suppress high frequency input interactions. The outputs of the converter modules are linked together in series and connected to the input of the transmission line to the load through a decoupling and line matching network. The dc-dc converter modules are phase activated such that for n modules, each module is activated equally 360.degree./n out of phase with respect to a successive module. The phased activation of the converter modules, combined with the square current waveforms out of the step up transformers, allows the power supply to operate with greatly reduced output capacitance values which minimizes the stored energy available for discharge into an electron beam gun or the like during arcing. The present power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle using simulated voltage feedback signals and voltage feedback loops. Circuitry is also provided for sensing incipient arc currents reflected at the output of the power supply and for simultaneously decoupling the power supply circuitry from the arcing load.

  13. Role of mitochondria in the switch mechanism of the cell death mode from apoptosis to necrosis--studies on rho0 cells.

    PubMed

    Wochna, Agnieszka; Niemczyk, Edyta; Kurono, Chieko; Masaoka, Makoto; Majczak, Anna; Kedzior, Jakub; Slominska, Ewa; Lipinski, Marcin; Wakabayashi, Takashi

    2005-04-01

    Detailed mechanisms of the switch of the cell death mode from apoptosis to necrosis remain to be solved, although the intracellular level of ATP and that of free radicals have been postulated to be the major factors involved in the mechanisms. In the present study menadione (MEN)-induced cell injury processes were studied using rho0 cells derived from human osteosarcoma 143B cells and parental rho+ cells co-treated with inhibitors of electron transfer chain of mitochondria or oligomycin, an inhibitor of ATP synthesis. Treatment of rho+ cells with 100 microM MEN induced apoptosis, which reached the maximum at 6 h, and was followed by an abrupt decrease thereafter, while necrotic cells (NC) increased continuously when they were judged by Annexin V and PI double staining. On the other hand, MEN induced apoptotic and necrotic changes much faster in rho0 cells compared to rho+ cells. The frequency to find apoptotic cells (AP) in the former cells was distinctly smaller than that to find NC judged by Annexin V and PI double staining. Electron microscopically, a major population of rho0 cells treated with MEN for 6 h consisted of intermediate cells, and a small number of AP co-existed. At 9 h of the treatment intermediate cells were exclusively seen, and AP were hardly detected. When parental rho+ cells were treated with MEN in the presence of oligomycin or oligomycin plus antimycin A both apoptotic and necrotic changes of the cells were distinctly accelerated. The intracellular level of superoxide in rho0 cells continuously increased after the MEN treatment, whereas that of ATP remained distinctly low before and after the MEN treatment compared to that in rho+ cells. These data suggest that the intracellular level of superoxide may be a key factor controlling the switch from apoptosis to necrosis.

  14. Magnetometer Application for GAMMA-400 Telescope Switching into the Mode with Increased Low Energy Charged Particles Intensity Registration

    NASA Astrophysics Data System (ADS)

    Khyzhniak, E. V.; Arkhangelskaja, I. V.; Chasovikov, E. N.; Arkhangelskiy, A. I.; Topchiev, N. P.

    GAMMA-400 is an international project of a high apogee orbital astrophysical observatory for studying the characteristics of high-energy gamma-emission, electrons/positrons and light nuclei fluxes. The energy range for γ-rays and electrons/positrons registration in the main aperture is from ∼0.1 GeV to ∼3.0 TeV. Also, this aperture allows high energy light nuclei fluxes characteristics investigation. Moreover, special aperture configuration allows registering of gamma-quanta, electrons (positrons) and light nuclei from the lateral directions too. The spacecraft GAMMA-400 orbit will be located in the Earth's magnetosphere and will pass front shock wave from magnetosphere interaction with the solar wind, turbulent-transition region, magnetopause and so on. During the satellite's movement through various Earth's magnetosphere regions its anticoincidence detectors will register high intensity fluxes of low energy charged particles captured by the magnetic field. The working area sections of GAMMA-400 detector systems used as anticoincidence shield are about 1 m2 each. The high intensity low energy charged particles flux influence on anticoincidence detectors should be taken into account during particle identification. This article presents a comparison between Earth's magnetosphere theoretical model according to SPENVIIS package and real data measured by detectors onboard THEMIS series satellites. The differences between these two datasets indicate that the calculated data are not sufficient to make short time predictions of variations of magnetic induction in the outer magnetosphere. A special trigger marker flag will be produced by GAMMA-400 counting and triggers signals formation system accordingly to the data of two onboard magnetometers. This flag's presence leads to special algorithms execution start, putting the plastic detectors into a dedicated working mode taking into account possible high count rates of external detector layers.

  15. Photovoltaic pumping system - Comparative study analysis between direct and indirect coupling mode

    NASA Astrophysics Data System (ADS)

    Harrag, Abdelghani; Titraoui, Abdessalem; Bahri, Hamza; Messalti, Sabir

    2017-02-01

    In this paper, P&O algorithm is used in order to improve the performance of photovoltaic water pumping system in both dynamic and static response. The efficiency of the proposed algorithm has been studied successfully using a DC motor-pump powered using controller by thirty six PV modules via DC-DC boost converter derived by a P&O MPPT algorithm. Comparative study results between the direct and indirect modes coupling confirm that the proposed algorithm can effectively improve simultaneously: accuracy, rapidity, ripple and overshoot.

  16. Optimization on the Thickness of Organic Insulator Layer for Advanced Super-In-Plane Switching Mode Thin-Film-Transistor Liquid Crystal Displays

    NASA Astrophysics Data System (ADS)

    Lin, Jiunn-Shyong; Yang, Kei-Hsiung; Chen, Shu-Hsia

    2005-08-01

    The growth rate of thin-film-transistor liquid crystal display (TFT-LCD) industries is faster than predicted due to the possible replacement of a cathode-ray tube television (CRT-TV) by a liquid crystal display television (LCD-TV). The in-plane switching (IPS) mode has been known as an excellent technology for realizing a wide viewing angle for LCD-TV, but it has the drawback of a low aperture ratio. An advanced super-IPS (AS-IPS) structure with an organic insulator layer was invented to achieve a high aperture ratio with increasing manufacturing cost. In this paper, we proposed a simple method of analyzing the optimum thickness of the organic insulator layer for AS-IPS. We derived the capacitive coupling ratio (CCR) of the IPS cell and analyzed the delay time of the AS-IPS panel to quantify the crosstalk properties. Furthermore, we also analyzed our electrode structure (AS'-IPS), which not only increases substantially the aperture ratio over that of AS-IPS but also reduces the crosstalk using the same optimized thickness of the organic insulator layer.

  17. Boosting the total ionizing dose tolerance of digital switches by using OCTO SOI MOSFET

    NASA Astrophysics Data System (ADS)

    Navarenho de Souza Fino, Leonardo; Davini Neto, Enrico; Aparecida Guazzelli da Silveira, Marcilei; Renaux, Christian; Flandre, Denis; Pinillos Gimenez, Salvador

    2015-10-01

    This paper performs an experimental comparative study of the total ionizing dose effects due to the x-ray radiation between the silicon-on-insulator (SOI) metal-oxide semiconductor field-effect transistors (MOSFETs) manufactured with octagonal gate geometry and the standard counterpart. Our main focus is on integrated transceivers for wireless communications and smart-power dc/dc converters for mobile electronics, where the transistor is used as the key switching element. It is shown that this innovative layout can reduce the total ionizing dose (TID) effects due to the special characteristics of the OCTO SOI MOSFET bird’s beak regions, where longitudinal electrical field lines in these regions are not parallel to the drain and source regions. Consequently, the parasitic MOSFETs associated with these regions are practically deactivated.

  18. An improved switching converter model. Ph.D. Thesis. Final Report

    NASA Technical Reports Server (NTRS)

    Shortt, D. J.

    1982-01-01

    The nonlinear modeling and analysis of dc-dc converters in the continuous mode and discontinuous mode was done by averaging and discrete sampling techniques. A model was developed by combining these two techniques. This model, the discrete average model, accurately predicts the envelope of the output voltage and is easy to implement in circuit and state variable forms. The proposed model is shown to be dependent on the type of duty cycle control. The proper selection of the power stage model, between average and discrete average, is largely a function of the error processor in the feedback loop. The accuracy of the measurement data taken by a conventional technique is affected by the conditions at which the data is collected.

  19. Thermionic gas switch

    DOEpatents

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

    1984-04-05

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

  20. Specification, Measurement, and Control of Electrical Switching Transients

    NASA Technical Reports Server (NTRS)

    Javor, K.

    1999-01-01

    There have been several instances of susceptibility to switching transients. The Space Shuttle Spacelab Remote Acquisition Unit (RAU-A standard interface between Spacelab payloads and the Shuttle communications system) will shut down if the input 28 Vdc bus drops below 22 volts for more than 80 gs. Although a MIL-STD-461 derivative CS06 requirement was levied on the RAU, it failed to find this susceptibility. A heavy payload on one aircraft sags the 28 volt bus below 20 volts for milliseconds. Dc-dc converters have an operating voltage. A typical 28 Vdc-to-5 Vdc converter operates within tolerance when input potential is between 17-40 Vdc, A hold-up capacitor can be used to extend the time this range is presented to the convener when the line potential sags or surges outside this range. The designer must know the range of normal transients in order to choose the correct value of hold-up. This report describes the phenomena of electrical power bus transients induced by the switching of loads both on and off the bus, and control thereof.

  1. Hybrid Voltage-Multipliers Based Switching Power Converters

    NASA Astrophysics Data System (ADS)

    Rosas-Caro, Julio C.; Mayo-Maldonado, Jonathan C.; Vazquez-Bautista, Rene Fabian; Valderrabano-Gonzalez, Antonio; Salas-Cabrera, Ruben; Valdez-Resendiz, Jesus Elias

    2011-08-01

    This work presents a derivation of PWM DC-DC hybrid converters by combining traditional converters with the Cockcroft-Walton voltage multiplier, the voltage multiplier of each converter is driven with the same transistor of the basic topology; this fact makes the structure of the new converters very simple and provides high-voltage gain. The traditional topologies discussed are the boost, buck-boost, Cuk and SEPIC. They main features of the discussed family are: (i) high-voltage gain without using extreme duty cycles or transformers, which allow high switching frequency and (ii) low voltage stress in switching devices, along with modular structures, and more output levels can be added without modifying the main circuit, which is highly desirable in some applications such as renewable energy generation systems. It is shown how a multiplier converter can become a generalized topology and how some of the traditional converters and several state-of-the-art converters can be derived from the generalized topologies and vice-versa. All the discussed converters were simulated, additionally experimental results are provided with an interleaved multiplier converter.

  2. Optimization of the pulse-width of diode-pumped passively Q-switched mode-locked c-cut Nd:GdVO4 laser with a GaAs saturable absorber.

    PubMed

    Han, Chao; Zhao, Shengzhi; Li, Dechun; Li, Guiqiu; Yang, Kejian; Zhang, Gang; Cheng, Kang

    2011-11-01

    By considering the single-photon absorption and two-photon absorption processes in the GaAs saturable absorber, the coupled rate equations for a diode-pumped passively Q-switched and mode-locked (QML) laser with GaAs coupler under Gaussian approximation are given. These rate equations are solved numerically. The key parameters of an optimally coupled passively QML laser with the shortest pulse-width envelope are determined. These key parameters include the parameters of the gain medium, the saturable absorber, and the resonator, which can minimize the pulse-width of a singly Q-switched envelope. Sample calculations for a diode-pumped passively Q-switched mode-locked c-cut Nd:GdVO(4) laser with a GaAs coupler are presented to demonstrate that the shortest pulse-width envelope can be obtained by selecting the optimal small-signal transmission of the saturable absorber and the reflectivity of the output mirror.

  3. A dual-loss-modulated Q-switched and mode-locked Nd:GdVO4 laser with AOM and V3 + :YAG saturable absorber at 1.34 µm

    NASA Astrophysics Data System (ADS)

    Zhang, Gang; Zhao, Shengzhi; Li, Yufei; Li, Guiqiu; Li, Dechun; Yang, Kejian; Cheng, Kang

    2011-03-01

    Stable and robust pulses can be generated in a diode-pumped Q-switched and mode-locked (QML) c-cut Nd:GdVO4/V3 + :YAG laser at 1.34 µm by inserting an acousto-optic modulator (AOM) into the laser cavity. In this kind of dual-loss-modulation QML laser, the pulse width of the Q-switched pulse envelope has a compression of 68% and the pulse energy has an improvement of seven times compared with that in the solely passively QML laser with V3 + :YAG. By considering the influence of the turnoff time and the modulation frequency of the AOM as well as the thermal lens effect, a developed rate equation model for dual-loss-modulation QML lasers is given and the numerical solutions of the rate equations are in good agreement with the experimental results.

  4. Numerical solutions of diode-pumped dual-loss-modulated Q-switched and mode-locked green laser with acousto-optic modulator and Cr 4+: YAG saturable absorber

    NASA Astrophysics Data System (ADS)

    Zhang, Gang; Zhao, Shengzhi; Li, Dechun; Yang, Kejian; Li, Guiqiu; Cheng, Kang; Zhang, Yan

    2011-04-01

    By considering the influence of the acousto-optic (AO) modulator and the nonlinear loss due to harmonic conversion in the intra-cavity frequency-doubling laser, a developed rate equation model for diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:LuVO4/KTP green laser with acousto-optic (AO) modulator and Cr4+:YAG saturable absorber is presented. With this developed model, the pulse width, single-pulse energy and the other dual-loss-modulated QML green laser characteristics are numerically simulated. The simulation results show that the turnoff time is of great importance for the pulse energy and pulse width of the Q-switched pulse. A diode-pumped dual-loss-modulated QML Nd:LuVO4/KTP laser is constructed to successfully demonstrate the numerical simulation application.

  5. The structure of mode-locking regions of piecewise-linear continuous maps: I. Nearby mode-locking regions and shrinking points

    NASA Astrophysics Data System (ADS)

    Simpson, D. J. W.

    2017-01-01

    The mode-locking regions of a dynamical system are subsets of parameter space within which there exists an attracting periodic solution. For piecewise-linear continuous maps, these regions have a distinctive chain structure with points of zero width called shrinking points. In this paper a local analysis about an arbitrary shrinking point is performed. This is achieved by studying the symbolic itineraries of periodic solutions in nearby mode-locking regions and performing an asymptotic analysis on one-dimensional centre manifolds in order to build a comprehensive theoretical framework for the local dynamics. The main results are universal quantitative descriptions for the shape of nearby mode-locking regions, the location of nearby shrinking points, and the key properties of these shrinking points. The results are applied to the three-dimensional border-collision normal form, a model of an oscillator subject to dry friction, and a model of a DC/DC power converter.

  6. Resistance switching mode transformation in SrRuO3/Cr-doped SrZrO3/Pt frameworks via a thermally activated Ti out-diffusion process

    PubMed Central

    Jo, Yongcheol; Jung, Kyooho; Kim, Jongmin; Woo, Hyeonseok; Han, Jaeseok; Kim, Hyungsang; Hong, Jinpyo; Lee, Jeon-Kook; Im, Hyunsik

    2014-01-01

    This work reports on a mechanism for irreversible resistive switching (RS) transformation from bipolar to unipolar RS behavior in SrRuO3 (SRO)/Cr-doped SrZrO3 (SZO:Cr)/Pt capacitor structures prepared on a Ti/SiO2/Si substrate. Counter-clockwise bipolar RS memory current-voltage (I–V) characteristics are observed within the RS voltage window of −2.5 to +1.9 V, with good endurance and retention properties. As the bias voltage increases further beyond 4 V under a forward bias, a forming process occurs resulting in irreversible RS mode transformation from bipolar to unipolar mode. This switching mode transformation is a direct consequence of thermally activated Ti out-diffusion from a Ti adhesion layer. Transition metal Ti effectively out-diffuses through the loose Pt electrode layer at high substrate temperatures, leading to the unintended formation of a thin titanium oxide (TiOx where x < 2) layer between the Pt electrode and the SZO:Cr layer as well as additional Ti atoms in the SZO:Cr layer. Cross-sectional scanning electron microscopy, transmission electron microscopy and Auger electron spectroscopy depth-profile measurements provided apparent evidence of the Ti out-diffusion phenomenon. We propose that the out-diffusion-induced additional Ti atoms in the SZO:Cr layer contributes to the creation of the metallic filamentary channels. PMID:25483325

  7. Resistance switching mode transformation in SrRuO3/Cr-doped SrZrO3/Pt frameworks via a thermally activated Ti out-diffusion process.

    PubMed

    Jo, Yongcheol; Jung, Kyooho; Kim, Jongmin; Woo, Hyeonseok; Han, Jaeseok; Kim, Hyungsang; Hong, Jinpyo; Lee, Jeon-Kook; Im, Hyunsik

    2014-12-08

    This work reports on a mechanism for irreversible resistive switching (RS) transformation from bipolar to unipolar RS behavior in SrRuO3 (SRO)/Cr-doped SrZrO3 (SZO:Cr)/Pt capacitor structures prepared on a Ti/SiO2/Si substrate. Counter-clockwise bipolar RS memory current-voltage (I-V) characteristics are observed within the RS voltage window of -2.5 to +1.9 V, with good endurance and retention properties. As the bias voltage increases further beyond 4 V under a forward bias, a forming process occurs resulting in irreversible RS mode transformation from bipolar to unipolar mode. This switching mode transformation is a direct consequence of thermally activated Ti out-diffusion from a Ti adhesion layer. Transition metal Ti effectively out-diffuses through the loose Pt electrode layer at high substrate temperatures, leading to the unintended formation of a thin titanium oxide (TiO(x) where x < 2) layer between the Pt electrode and the SZO:Cr layer as well as additional Ti atoms in the SZO:Cr layer. Cross-sectional scanning electron microscopy, transmission electron microscopy and Auger electron spectroscopy depth-profile measurements provided apparent evidence of the Ti out-diffusion phenomenon. We propose that the out-diffusion-induced additional Ti atoms in the SZO:Cr layer contributes to the creation of the metallic filamentary channels.

  8. Avalanche mode of high-voltage overloaded p{sup +}–i–n{sup +} diode switching to the conductive state by pulsed illumination

    SciTech Connect

    Kyuregyan, A. S.

    2015-07-15

    A simple analytical theory of the picosecond switching of high-voltage overloaded p{sup +}–i–n{sup +} photodiodes to the conductive state by pulsed illumination is presented. The relations between the parameters of structure, light pulse, external circuit, and main process characteristics, i.e., the amplitude of the active load current pulse, delay time, and switching duration, are derived and confirmed by numerical simulation. It is shown that the picosecond light pulse energy required for efficient switching can be decreased by 6–7 orders of magnitude due to the intense avalanche multiplication of electrons and holes. This offers the possibility of using pulsed semiconductor lasers as a control element of optron pairs.

  9. Optical packet switching

    NASA Astrophysics Data System (ADS)

    Shekel, Eyal; Ruschin, Shlomo; Majer, Daniel; Levy, Jeff; Matmon, Guy; Koenigsberg, Lisa; Vecht, Jacob; Geron, Amir; Harlavan, Rotem; Shfaram, Harel; Arbel, Arnon; McDermott, Tom; Brewer, Tony

    2005-02-01

    We report here a scalable, multichassis, 6.3 terabit core router, which utilizes our proprietary optical switch. The router is commercially available and deployed in several customer sites. Our solution combines optical switching with electronic routing. An internal optical packet switching network interconnects the router"s electronic line cards, where routing and buffering functions take place electronically. The system architecture and performance will be described. The optical switch is based on Optical Phased Array (OPA) technology. It is a 64 x 64, fully non-blocking, optical crossbar switch, capable of switching in a fraction of a nanosecond. The basic principles of operation will be explained. Loss and crosstalk results will be presented, as well as the results of BER measurements of a 160 Gbps transmission through one channel. Basic principles of operation and measured results will be presented for the burst-mode-receivers, arbitration algorithm and synchronization. Finally, we will present some of our current research work on a next-generation optical switch. The technological issues we have solved in our internal optical packet network can have broad applicability to any global optical packet network.

  10. Switch wear leveling

    DOEpatents

    Wu, Hunter; Sealy, Kylee; Gilchrist, Aaron

    2015-09-01

    An apparatus for switch wear leveling includes a switching module that controls switching for two or more pairs of switches in a switching power converter. The switching module controls switches based on a duty cycle control technique and closes and opens each switch in a switching sequence. The pairs of switches connect to a positive and negative terminal of a DC voltage source. For a first switching sequence a first switch of a pair of switches has a higher switching power loss than a second switch of the pair of switches. The apparatus includes a switch rotation module that changes the switching sequence of the two or more pairs of switches from the first switching sequence to a second switching sequence. The second switch of a pair of switches has a higher switching power loss than the first switch of the pair of switches during the second switching sequence.

  11. Photoconductive switching for high power microwave generation

    SciTech Connect

    Pocha, M.D.; Hofer, W.W.

    1990-10-01

    Photoconductive switching is a technology that is being increasingly applied to generation of high power microwaves. Two primary semiconductors used for these devices are silicon and gallium arsenide. Diamond is a promising future candidate material. This paper discusses the important material parameters and switching modes, critical issues for microwave generation, and future directions for this high power, photoconductive switching technology.

  12. A gain-coefficient switched Alexandrite laser

    NASA Astrophysics Data System (ADS)

    Lee, Chris J.; van der Slot, Peter J. M.; Boller, Klaus-J.

    2013-01-01

    We report on a gain-coefficient switched Alexandrite laser. An electro-optic modulator is used to switch between high and low gain states by making use of the polarization dependent gain of Alexandrite. In gain-coefficient switched mode, the laser produces 85 ns pulses with a pulse energy of 240 mJ at a repetition rate of 5 Hz.

  13. A Multi-Level Grid Interactive Bi-directional AC/DC-DC/AC Converter and a Hybrid Battery/Ultra-capacitor Energy Storage System with Integrated Magnetics for Plug-in Hybrid Electric Vehicles

    SciTech Connect

    Onar, Omer C

    2011-01-01

    This study presents a bi-directional multi-level power electronic interface for the grid interactions of plug-in hybrid electric vehicles (PHEVs) as well as a novel bi-directional power electronic converter for the combined operation of battery/ultracapacitor hybrid energy storage systems (ESS). The grid interface converter enables beneficial vehicle-to-grid (V2G) interactions in a high power quality and grid friendly manner; i.e, the grid interface converter ensures that all power delivered to/from grid has unity power factor and almost zero current harmonics. The power electronic converter that provides the combined operation of battery/ultra-capacitor system reduces the size and cost of the conventional ESS hybridization topologies while reducing the stress on the battery, prolonging the battery lifetime, and increasing the overall vehicle performance and efficiency. The combination of hybrid ESS is provided through an integrated magnetic structure that reduces the size and cost of the inductors of the ESS converters. Simulation and experimental results are included as prove of the concept presenting the different operation modes of the proposed converters.

  14. A 1.5 ns OFF/ON switching-time voltage-mode LVDS driver/receiver pair for asynchronous AER bit-serial chip grid links with up to 40 times event-rate dependent power savings.

    PubMed

    Zamarreno-Ramos, Carlos; Kulkarni, Raghavendra; Silva-Martinez, Jose; Serrano-Gotarredona, Teresa; Linares-Barranco, Bernabe

    2013-10-01

    This paper presents a low power fast ON/OFF switchable voltage mode implementation of a driver/receiver pair intended to be used in high speed bit-serial Low Voltage Differential Signaling (LVDS) Address Event Representation (AER) chip grids, where short (like 32-bit) sparse data packages are transmitted. Voltage-Mode drivers require intrinsically half the power of their Current-Mode counterparts and do not require Common-Mode Voltage Control. However, for fast ON/OFF switching a special high-speed voltage regulator is required which needs to be kept ON during data pauses, and hence its power consumption must be minimized, resulting in tight design constraints. A proof-of-concept chip test prototype has been designed and fabricated in low-cost standard 0.35 μ m CMOS. At ± 500 mV voltage swing with 500 Mbps serial bit rate and 32 bit events, current consumption scales from 15.9 mA (7.7 mA for the driver and 8.2 mA for the receiver) at 10 Mevent/s rate to 406 μ A ( 343 μ A for the driver and 62.5 μA for the receiver) for an event rate below 10 Kevent/s, therefore achieving a rate dependent power saving of up to 40 times, while keeping switching times at 1.5 ns. Maximum achievable event rate was 13.7 Meps at 638 Mbps serial bit rate. Additionally, differential voltage swing is tunable, thus allowing further power reductions.

  15. Coaxial Switch

    DTIC Science & Technology

    2014-04-23

    08-2015 Publication Coaxial Switch David J. Bamford et al Naval Undersea Warfare Center Division, Newport 1176 Howell Street, Bldg 102T, Code 00L...Distribution A A coaxial switch having a housing and a shaft extending through and rotatably mounted to the housing. The shaft extends from opposite...conductor members are electrically connected together. When the coaxial switch is engaged, the conductor members are inserted into the connector body

  16. Impact of oxygen stoichiometry on electroforming and multiple switching modes in TiN/TaOx/Pt based ReRAM

    NASA Astrophysics Data System (ADS)

    Sharath, S. U.; Joseph, M. J.; Vogel, S.; Hildebrandt, E.; Komissinskiy, P.; Kurian, J.; Schroeder, T.; Alff, L.

    2016-10-01

    We have investigated the material and electrical properties of tantalum oxide thin films (TaOx) with engineered oxygen contents grown by RF-plasma assisted molecular beam epitaxy. The optical bandgap and the density of the TaOx films change consistently with oxygen contents in the range of 3.63 to 4.66 eV and 12.4 to 9.0 g/cm3, respectively. When exposed to atmosphere, an oxidized Ta2O5-y surface layer forms with a maximal thickness of 1.2 nm depending on the initial oxygen deficiency of the film. X-ray photoelectron spectroscopy studies show that multiple sub-stoichiometric compositions occur in oxygen deficient TaOx thin films, where all valence states of Ta including metallic Ta are possible. Devices of the form Pt/Ta2O5-y/TaOx/TiN exhibit highly tunable forming voltages of 10.5 V to 1.5 V with decreasing oxygen contents in TaOx. While a stable bipolar resistive switching (BRS) occurs in all devices irrespective of oxygen content, unipolar switching was found to coexist with BRS only at higher oxygen contents, which transforms to a threshold switching behaviour in the devices grown under highest oxidation.

  17. Derivation of linearized transfer functions for switching-mode regulations. Phase A: Current step-up and voltage step-up converters

    NASA Technical Reports Server (NTRS)

    Wong, R. C.; Owen, H. A., Jr.; Wilson, T. G.

    1981-01-01

    Small-signal models are derived for the power stage of the voltage step-up (boost) and the current step-up (buck) converters. The modeling covers operation in both the continuous-mmf mode and the discontinuous-mmf mode. The power stage in the regulated current step-up converter on board the Dynamics Explorer Satellite is used as an example to illustrate the procedures in obtaining the small-signal functions characterizing a regulated converter.

  18. Optical switches and switching methods

    DOEpatents

    Doty, Michael

    2008-03-04

    A device and method for collecting subject responses, particularly during magnetic imaging experiments and testing using a method such as functional MRI. The device comprises a non-metallic input device which is coupled via fiber optic cables to a computer or other data collection device. One or more optical switches transmit the subject's responses. The input device keeps the subject's fingers comfortably aligned with the switches by partially immobilizing the forearm, wrist, and/or hand of the subject. Also a robust nonmetallic switch, particularly for use with the input device and methods for optical switching.

  19. High-power actively Q-switched single-mode 1342 nm Nd:YVO4 ring laser, injection-locked by a cw single-frequency microchip laser.

    PubMed

    Koch, Peter; Bartschke, Juergen; L'huillier, Johannes A

    2015-11-30

    In this paper we report on the realization of a single-mode Q-switched Nd:YVO4 ring laser at 1342 nm. Unidirectional and single-mode operation of the ring laser is achieved by injection-locking with a continuous wave Nd:YVO4 microchip laser, emitting a single-frequency power of up to 40 mW. The ring laser provides a single-mode power of 13.9 W at 10 kHz pulse repetition frequency with a pulse duration of 18.2 ns and an excellent beam quality (M2 < 1.05). By frequency doubling of the fundamental 1342 nm laser, a power of 8.7 W at 671 nm with a pulse duration of 14.8 ns and a beam propagation factor of M2 < 1.1 is obtained. The 671 nm radiation features a long-term spectral width of 75 MHz.

  20. ION SWITCH

    DOEpatents

    Cook, B.

    1959-02-10

    An ion switch capable of transferring large magnitudes of power is described. An ion switch constructed in accordance with the invention includes a pair of spaced control electrodes disposed in a highly evacuated region for connection in a conventional circuit to control the passing of power therethrough. A controllable ionic conduction path is provided directiy between the control electrodes by a source unit to close the ion switch. Conventional power supply means are provided to trigger the source unit and control the magnitude, durations and pulse repetition rate of the aforementioned ionic conduction path.

  1. Composite Material Switches

    NASA Technical Reports Server (NTRS)

    Javadi, Hamid (Inventor)

    2001-01-01

    A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

  2. Retrospective analysis of melasma treatment using a dual mode of low-fluence Q-switched and long-pulse Nd:YAG laser vs. low-fluence Q-switched Nd:YAG laser monotherapy.

    PubMed

    Choi, Chun Pil; Yim, Seon Mi; Seo, Soo Hong; Ahn, Hyo Hyun; Kye, Young Chul; Choi, Jae Eun

    2015-02-01

    Despite the effectiveness of low-fluence Q-switched Nd:YAG laser (QSNY) treatment in melasma, adverse events, including mottled hypopigmentation (MH) and rebound hyperpigmentation (RH) have been reported. To compare the effectiveness and safety of combination therapy using low-fluence QSNY and long-pulse Nd:YAG laser (LPNY) (Dual toning), with low-fluence QSNY monotherapy (QS toning), in Asian melasma patients. Patients were treated for 10 sessions at 1-week intervals with QSNY (6 mm spot); 2.5-3.0 J/cm(2) for QS toning (n = 177) or 2.1-2.5 J/cm(2) for dual toning (n = 183). The dual toning group was immediately treated with LPNY (7 mm spot, 15-17 J/cm(2)). The results were evaluated using the modified Melasma Area and Severity Index (mMASI) score and the physician's global assessment. MH or RH were significantly lower (1.1% vs. 14.1%) and the treatment efficacy was improved (median decrease of mMASI, 3.6 vs. 3.0) in the dual toning group compared with the QS toning group. Periorbital melasma showed distinctively high rates of adverse events in the QS toning group (23.9% vs. 5.7%), which were significantly reduced in the dual toning group (2.9%). Dual toning could represent a safe and effective treatment for Asian melasma patients, as it is associated with minimal adverse events and improved treatment efficacy compared with QS toning monotherapy.

  3. Innovative switching technology

    NASA Astrophysics Data System (ADS)

    Rosen, A.; Stabile, P. J.; Gombar, A. M.; Janton, W. M.; Gilbert, D. B.; Herczfeld, P. R.; Bahasadri, A.

    1991-03-01

    We have developed an all-semiconductor high-power optical switch. Potential uses include both military applications, such as ultra-wide-band impulse radar and high-frequency antenna couplers, and commercial use, such as high-power switching for utility companies. Under this three-year program, we have demonstrated various switching applications from dc to GHz frequencies. The generic switches comprise a 2-D semiconductor laser diode array and Si or GaAs devices. In the Si area (linear switches - no gain) and dc-biased network, a single two-sided PIN device, activated by two 1 kW laser arrays, has yielded a holding voltage of 1.3 kV and conducted 192 A. Similar devices have later yielded a holding voltage of 3.3 kV, demonstrating the capability of switching more than 500 kW with a single two-sided PIN device. The same generic technology was also demonstrated in high-power high-frequency antenna coupler applications as well as in mm-wave (60 GHz) attenuators and phase shifters. PIN devices tested in a RF circuit between 2-30 MHz yielded an isolation value of between 28 and 49 dB in the off-state, and insertion losses as low as 0.1 dB when illuminated with 280 W (peak) optical power at 808 nm. In the area of GaAs, PIN, and bulk devices under this project, we were able to deliver devices for experiments in both opening and closing switches. We have demonstrated a compact, all-semiconductor switch system that has switched up to 8.5 MW into a 38 (omega) load. The system uses a 2-D laser diode array with a peak power of 850 W to rigger a 1.5 cm long GaAs photoconductor into a high-gain combination mode known as 'lock on'. The highest power switch was pulse-charged to 55 kV and delivered 470 A to a 38 (omega) load in 160 ns long pulse. In the area of 2-D laser arrays, a peak power density of 7 kW/cm(exp 2) was achieved.

  4. Existence and switching behavior of bright and dark Kerr solitons in whispering-gallery mode resonators with zero group-velocity dispersion

    NASA Astrophysics Data System (ADS)

    Talla Mbé, Jimmi H.; Milián, Carles; Chembo, Yanne K.

    2017-07-01

    We use the generalized Lugiato-Lefever model to investigate the phenomenon of Kerr optical frequency comb generation when group-velocity dispersion is null. In that case, the first dispersion term that plays a leading role is third-order dispersion. We show that this term is sufficient to allow for the existence of both bright and dark solitons. We identify the areas in the parameter space where both kind of solitons can be excited inside the resonator. We also unveil a phenomenon of hysteretic switching between these two types of solitons when the power of the pump laser is cyclically varied. Contribution to the Topical Issue "Theory and Applications of the Lugiato-Lefever Equation", edited by Yanne K. Chembo, Damia Gomila, Mustapha Tlidi, Curtis R. Menyuk.

  5. DC-DC Power Conversion With Galvanic Isolation

    DTIC Science & Technology

    2003-06-01

    distribution schemes found aboard ships today. It will be necessary to maintain reliability while supplying the various components onboard with the...will be many changes to the power distribution schemes found aboard ships today. It will be necessary to maintain reliability while supplying the...and 4 ......................................................................................32 4. Weighting the Equations

  6. Prospective randomized controlled clinical and histopathological study of acne vulgaris treated with dual mode of quasi-long pulse and Q-switched 1064-nm Nd:YAG laser assisted with a topically applied carbon suspension.

    PubMed

    Jung, Jae Yoon; Hong, Jong Soo; Ahn, Chang Ho; Yoon, Ji Young; Kwon, Hyuck Hoon; Suh, Dae Hun

    2012-04-01

    Acne treatments using laser and light devices have been reported to have varying degrees of efficacy. However, there has been no study of treatment of acne using a dual mode (quasi-long pulse and Q-switched mode) 1064-nm Nd:YAG laser assisted with a topically applied carbon suspension. To evaluate the clinical efficacy, safety, and histological changes of new laser treatment method for acne vulgaris. Twenty-two patients received 3 sessions of quasi-long pulse and Q-switched Nd:YAG laser treatment assisted with a topically applied carbon suspension at 2-week intervals in a randomized split face manner. At the final visit, the inflammatory acne lesions were reduced on the laser-treated side by 58.6% (P < .001), but increased on the untreated side by 5%. The noninflammatory acne lesions were reduced on the laser-treated side by 52.4% (P < .001). Sebum output reduction, inflammatory cell and cytokine reductions, a decrease of the thickness of a perifollicular stratum corneum and a full epithelium, and skin rejuvenation effect were found. The histopathologic examination of the acne lesions showed decreased inflammation and immunostaining intensity for interleukin 8, matrix metalloproteinase-9, toll-like receptor-2, and nuclear factor kappa B, and tumor necrosis factor alpha was reduced significantly. No severe adverse reactions were reported. All patients reported mild transient erythema that disappeared in a few hours. The number of subjects studied was small. This laser treatment was rapid and effective for treating not only the inflammatory but also the noninflammatory acne lesions when compared with the control side. The histopathologic findings correlated well with the clinical acne grade and treatment response. This novel laser treatment appears to be safe and effective for acne treatment. Copyright © 2012 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.

  7. Arterial switch.

    PubMed

    Planche, C; Lacour-Gayet, F; Serraf, A

    1998-01-01

    A relatively large spectra of anatomic variations are found within the unifying features of discordant ventriculoarterial connections. Variants that lend themselves to anatomic repair by the arterial switch operation are discussed, these include transposition of the great arteries with intact ventricular septum (TGA IVS), TGA associated with a ventricular septal defect (TGA VSD), double-outlet right ventricle with subpulmonary VSD (DORV VSD), and TGA or DORV with VSD associated with coarctation. Double discordance with VSD, which is currently treated by double switch or Rastelli and atrial switch and which probably represents, in our department, the only remaining indication for atrial switch, is not discussed. Also, we exclude TGA associated with pulmonary stenosis, which is treated by Rastelli or REV operation.

  8. Magnetic switching

    NASA Astrophysics Data System (ADS)

    Kirbie, H. C.

    1989-04-01

    Magnetic switching is a pulse compression technique that uses a saturable inductor (reactor) to pass pulses of energy between two capacitors. A high degree of pulse compression can be achieved in a network when several of these simple, magnetically switched circuits are connected in series. Individual inductors are designed to saturate in cascade as a pulse moves along the network. The technique is particularly useful when a single-pulse network must be very reliable or when a multi-pulse network must operate at a high pulse repetition frequency (PRF). Today, magnetic switches trigger spark gaps, sharpen the risetimes of high energy pulses, power large lasers, and drive high PRF linear induction accelerators. This paper will describe the technique of magnetic pulse compression using simple networks and design equations. A brief review of modern magnetic materials and of their role in magnetic switch design will be presented.

  9. Acceleration switch

    DOEpatents

    Abbin, J.P. Jr.; Devaney, H.F.; Hake, L.W.

    1979-08-29

    The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

  10. Acceleration switch

    DOEpatents

    Abbin, Jr., Joseph P.; Devaney, Howard F.; Hake, Lewis W.

    1982-08-17

    The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

  11. Nucleosome Switches

    NASA Astrophysics Data System (ADS)

    Schwab, David J.; Bruinsma, Robijn F.; Rudnick, Joseph; Widom, Jonathan

    2008-06-01

    We present a statistical-mechanical model for the positioning of nucleosomes along genomic DNA molecules as a function of the strength of the binding potential and the chemical potential of the nucleosomes. We show that a significant section of the DNA is composed of two-level nucleosome switching regions where the nucleosome distribution undergoes a localized, first-order transition. The location of the nucleosome switches shows a strong correlation with the location of gene-regulation regions.

  12. Nucleosome switches.

    PubMed

    Schwab, David J; Bruinsma, Robijn F; Rudnick, Joseph; Widom, Jonathan

    2008-06-06

    We present a statistical-mechanical model for the positioning of nucleosomes along genomic DNA molecules as a function of the strength of the binding potential and the chemical potential of the nucleosomes. We show that a significant section of the DNA is composed of two-level nucleosome switching regions where the nucleosome distribution undergoes a localized, first-order transition. The location of the nucleosome switches shows a strong correlation with the location of gene-regulation regions.

  13. Side mode suppression and dispersion compensation analysis of a 60 GHz radio-over-fibre system based on a gain switched laser

    NASA Astrophysics Data System (ADS)

    Martin, Eamonn; Barry, Liam

    2014-02-01

    The research and technical community have designated a band of 7 GHz between 57 and 64 GHz for short-range wireless communications. This paper utilizes a simple and cost effective technique for generating a 60 GHz millimeter-wave (mm-wave) signal using an optical comb source based on a gain-switched laser (GSL). This research investigates the effects unwanted comb lines have on the overall system performance with 2.5 Gb/s data transmission. To do this, a programmable optical filter is used to suppress the unwanted comb lines to varying levels. Bit-error rate (BER) measurements were carried out against received optical power to demonstrate the detrimental effects the unwanted comb lines have on the modulated mm-wave signal when not sufficiently suppressed. As chromatic dispersion is a limiting factor to the system's transmission distance, this work also investigates pre-compensation for dispersion utilizing the programmable group delay capabilities of the programmable optical filter, demonstrating the ability to extend the transmission distance by 12 km. All experimental results obtained are reinforced through simulation.

  14. Retreatment using a dual mode of low-fluence Q-switched and long-pulse Nd:YAG laser in patients with melasma aggravation after previous therapy.

    PubMed

    Choi, Chun Pil; Yim, Seon Mi; Seo, Soo Hong; Ahn, Hyo Hyun; Kye, Young Chul; Choi, Jae Eun

    2015-06-01

    Aggravated melasma after treatment is vulnerable to stimulation, can easily deteriorate, and may be distressing without proper management. To retrospectively assess the effectiveness and safety of combination therapy using low-fluence Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (QSNY) and long-pulse Nd:YAG laser (LPNY) (dual toning) in patients with rebound melasma. A total of 30 patients with aggravated melasma after previous therapy who were treated with dual toning were enrolled. A total of 10 sessions were conducted at 1-week intervals, followed by maintenance treatment. The results were evaluated using the modified Melasma Area and Severity Index (mMASI) and the physician's global assessment (PGA) before and 2 months after completing the 10 treatment sessions. The baseline mMASI was 10.48 ± 3.64, which significantly decreased to 3.22 ± 1.45 2 months after completing the 10 treatment sessions (p < 0.001). Twenty-four patients (80%) had PGA grade 4 (76-100% improvement) and 6 patients (20%) had PGA grade 3 (51-75% improvement). Dual toning may be a safe and effective salvage treatment for patients with aggravated melasma after previous treatment. LPNY may stabilize melasma activity to prevent rebound hyperpigmentation via dermal remodeling.

  15. Data center coolant switch

    DOEpatents

    Iyengar, Madhusudan K.; Parida, Pritish R.; Schultz, Mark D.

    2015-10-06

    A data center cooling system is operated in a first mode; it has an indoor portion wherein heat is absorbed from components in the data center, and an outdoor heat exchanger portion wherein outside air is used to cool a first heat transfer fluid (e.g., water) present in at least the outdoor heat exchanger portion of the cooling system during the first mode. The first heat transfer fluid is a relatively high performance heat transfer fluid (as compared to the second fluid), and has a first heat transfer fluid freezing point. A determination is made that an appropriate time has been reached to switch from the first mode to a second mode. Based on this determination, the outdoor heat exchanger portion of the data cooling system is switched to a second heat transfer fluid, which is a relatively low performance heat transfer fluid, as compared to the first heat transfer fluid. It has a second heat transfer fluid freezing point lower than the first heat transfer fluid freezing point, and the second heat transfer fluid freezing point is sufficiently low to operate without freezing when the outdoor air temperature drops below a first predetermined relationship with the first heat transfer fluid freezing point.

  16. Resistive switching in Ag-TiO2 contacts

    NASA Astrophysics Data System (ADS)

    Ghenzi, N.; Stoliar, P.; Fuertes, M. C.; Marlasca, F. G.; Levy, P.

    2012-08-01

    We study the electric pulse induced resistance switching of TiO2-Ag contacts at room temperature, exploring both unipolar and bipolar switching modes. Initially we observed unipolar response. After hundred pulsing cycles the unipolar switching response vanishes but the device can still be operated in bipolar switching regime. The underlying mechanism for resistance switching is modeled in terms of formation and rupture of filament, and movement of oxygen vacancies.

  17. Nucleus accumbens dopamine/glutamate interaction switches mode to generate desire versus dread: D1 alone for appetitive eating but D1 and D2 together for fear

    PubMed Central

    Richard, Jocelyn M.; Berridge, Kent C.

    2011-01-01

    The medial shell of nucleus accumbens (NAc) and its mesolimbic dopamine inputs mediate forms of fearful as well as of incentive motivation. For example, either appetitive and/or actively fearful behaviors are generated in a keyboard pattern by localized glutamate disruptions in NAc (via microinjection of AMPA receptor antagonist DNQX) at different anatomical locations along a rostrocaudal gradient within medial shell of rats. Rostral glutamate disruptions produce intense increases in eating, but more caudally placed disruptions produce increasingly fearful behaviors: distress vocalizations and escape attempts to human touch, and a spontaneous and directed antipredator response called defensive treading/burying. Local endogenous dopamine is required for either intense motivation to be generated by AMPA disruptions. Here we report that only endogenous local signaling at D1 dopamine receptors is needed for rostral generation of excessive eating, potentially implicating a direct output pathway contribution. By contrast, fear generation at caudal sites requires both D1 and D2 signaling simultaneously, potentially implicating an indirect output pathway contribution. Finally, when motivation valence generated by AMPA disruptions at intermediate sites was flipped by manipulating environmental ambience, from mostly appetitive in a comfortable home environment to mostly fearful in a stressful environment, the roles of local D1 versus D2 signaling in dopamine/glutamate interaction at microinjection sites also switched dynamically to match the motivation valence generated at the moment. Thus, NAc D1 and D2 receptors, and their associated neuronal circuits, play different and dynamic roles in enabling desire and dread to be generated by localized NAc glutamate disruptions in medial shell. PMID:21900565

  18. Nucleus accumbens dopamine/glutamate interaction switches modes to generate desire versus dread: D(1) alone for appetitive eating but D(1) and D(2) together for fear.

    PubMed

    Richard, Jocelyn M; Berridge, Kent C

    2011-09-07

    The medial shell of nucleus accumbens (NAc) and its mesolimbic dopamine inputs mediate forms of fearful as well as of incentive motivation. For example, either appetitive and/or actively fearful behaviors are generated in a keyboard pattern by localized glutamate disruptions in NAc (via microinjection of the AMPA receptor antagonist DNQX) at different anatomical locations along a rostrocaudal gradient within the medial shell of rats. Rostral glutamate disruptions produce intense increases in eating, but more caudally placed disruptions produce increasingly fearful behaviors: distress vocalizations and escape attempts to human touch, and a spontaneous and directed antipredator response called defensive treading/burying. Local endogenous dopamine is required for either intense motivation to be generated by AMPA disruptions. Here we report that only endogenous local signaling at D(1) dopamine receptors is needed for rostral generation of excessive eating, potentially implicating a direct output pathway contribution. In contrast, fear generation at caudal sites requires both D(1) and D(2) signaling simultaneously, potentially implicating an indirect output pathway contribution. Finally, when motivation valence generated by AMPA disruptions at intermediate sites was flipped by manipulating environmental ambience, from mostly appetitive in a comfortable home environment to mostly fearful in a stressful environment, the roles of local D(1) and D(2) signaling in dopamine/glutamate interaction at microinjection sites also switched dynamically to match the motivation valence generated at the moment. Thus, NAc D(1) and D(2) receptors, and their associated neuronal circuits, play different and dynamic roles in enabling desire and dread to be generated by localized NAc glutamate disruptions in medial shell.

  19. Single-Switch Equalization Charger Using Multiple Stacked Buck-Boost Converters for Series-Connected Energy-Storage Modules

    NASA Astrophysics Data System (ADS)

    Uno, Masatoshi; Tanaka, Koji

    Series connections of energy-storage modules such as electric double-layer capacitors (EDLCs) and lithium-ion batteries result in voltage imbalance because of the nonuniform properties of individual modules. Conventional voltage equalizers based on traditional dc-dc converters require numerous switches and/or transformers, and therefore, their costs and complexity tend to increase. This paper proposes a novel single-switch equalization charger using multiple stacked buck-boost converters. The single-switch operation not only reduces the circuit complexity but also contributes to increasing the reliability. The fundamental operating principles and design procedures of key components are presented in detail. An experimental charge test using a 25W prototype of the proposed equalization charger was performed for four series-connected EDLC modules whose initial voltages were intentionally imbalanced. Experimental results demonstrated that the proposed equalization charger could charge the series-connected modules preferentially in the order of increasing module voltage and that all the modules could be charged up to a uniform voltage level.

  20. Toward pulsed power uses for photoconductive semiconductor switches: Closing switches

    SciTech Connect

    Loubriel, G.M.; O'Malley, M.W.; Zutavern, F.J.

    1987-01-01

    Recent results on Photoconductive Semiconductor Switches (PCSS) are presented. For Si and GaAs switches surface flashover, contact degradation, and current limitations are addressed. For Si samples have been obtained that, without being triggered, withstand fields of up to 85 kV/cm produced by an approx.2-..mu..s wide voltage pulse. The 1-inch diameter, Si samples (''gap length'' of 1.5 cm) have been switched at 36 kV/cm (approx. =54 kV) into an approx.30-..cap omega.. load with a current of 703 A. For GaAs, most samples can withstand, without being triggered, 100 kV/cm. At low electric fields the GaAs samples behave as switches that close during the laser pulse and then open in nanoseconds. At high voltages GaAs does not open. In this mode, called lock-on, up to 42.7 kV/cm (64.1 kV) has been switched. The lock-on mode can be triggered with small laser powers. Plans are being made to use large arrays of GaAs samples to switch 1 MV and 156 kA.