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Sample records for voltage restorer based

  1. (ann) based dynamic voltage restorer

    African Journals Online (AJOL)

    HOD

    artificial intelligence to provide smart triggering pulses for the DVR to mitigate and to provide compensation against ... the starting of large induction motor [6]. ... ANN-based DVR under voltage sags and swells phenomena. In this case, the ANN is trained off-line, and the trained network is employed for on-line control.

  2. (ann) based dynamic voltage restorer

    African Journals Online (AJOL)

    HOD

    artificial intelligence to provide smart triggering pulses for the DVR to mitigate and to provide compensation against voltage sags and swells. The Artificial Neural Network (ANN) was trained ... 90% of the nominal rms value and lasting for 0.5cycles. (10msec for 50Hz power system) up to 1 minute. It is considered as the most ...

  3. DVR(Dynamic Voltage Restorer)

    Indian Academy of Sciences (India)

    First page Back Continue Last page Graphics. DVR(Dynamic Voltage Restorer). Supply voltage Sag compensation. Supply voltage Swell Compensation. Balancing the Load voltage. Compensation of Supply Voltage Harmonics.

  4. A Decentralized Multi-Agent-Based Approach for Low Voltage Microgrid Restoration

    Directory of Open Access Journals (Sweden)

    Ebrahim Rokrok

    2017-09-01

    Full Text Available Although a well-organized power system is less subject to blackouts, the existence of a proper restoration plan is nevertheless still essential. The goal of a restoration plan is to bring the power system back to its normal operating conditions in the shortest time after a blackout occurs and to minimize the impact of the blackout on society. This paper presents a decentralized multi-agent system (MAS-based restoration method for a low voltage (LV microgrid (MG. In the proposed method, the MG local controllers are assigned to the specific agents who interact with each other to achieve a common decision in the restoration procedure. The evaluation of the proposed decentralized technique using a benchmark low-voltage MG network demonstrates the effectiveness of the proposed restoration plan.

  5. Fuzzy Logic Controlled DC-DC Converter Based Dynamic Voltage Restorer

    Directory of Open Access Journals (Sweden)

    Mustafa İnci

    2015-12-01

    Full Text Available This paper presents fuzzy logic controlled dc-dc boost converter based Dynamic Voltage Restorer (DVR to compensate severe voltage sag problems in an electrical system. DVR absorbs real power from battery to compensate voltage sags in the system. This condition causes reduction in voltage magnitude of dc-link capacitor. Additionally, DVR requires large dc capacitors to compensate long and severe voltage sags in the system. In this study, dc-dc boost converter is connected to DVR for keeping dc link voltage constant. For this propose, a control algorithm based on Fuzzy Logic (FL control is developed for dc-dc boost converter. The main contribution of this study is that Fuzzy Logic (FL is firstly used to generate reference signal for PWM signals of dc-dc converter applied in DVR. FL is a very flexible controller which keeps the dc link voltage constant during voltage sag. The performance results of proposed study are verified with PSCAD/EMDTC.

  6. Dynamic Voltage Restorer Based on Combination of Feed Back and Feed Forward PI

    Directory of Open Access Journals (Sweden)

    Dimas Anton A

    2009-08-01

    Full Text Available Dynamic voltage restorer (DVR is one of equipments to protect sensitive load from voltage drop. DVR is installed series with line feeder by serial transformer which injecting voltage when under voltage occurs. This research is investigate the capability of DVR, which controlled by combination of feed back and feed forward PI, to handle voltage sag and interruption. DVR controls have been designed and implemented in DVR prototype. As a result, in simulation, DVR can maintain voltage in range 90% - 105% nominal voltage. Voltage at load side can be restored to 1 pu and 0.79 pu when voltage sag and interruption respectively. Furthermore, DVR prototype can restore 0.95 pu when voltage sag and 0.54 pu when interruption.

  7. Comparative Studies of Different Control Strategies of a Dynamic Voltage Restorer Based on Matrix Converter

    Directory of Open Access Journals (Sweden)

    Amin Shabanpour

    2012-01-01

    Full Text Available A dynamic voltage restorer (DVR with no energy storage is studied. By using a matrix converter instead of the conventional AC/DC/AC converters, elimination of the DC-link capacitor is possible. The switching algorithm of matrix converter is the space vector modulation. There are different compensation algorithms to control the conventional DVR. These methods have been analyzed in this paper for the proposed matrix-converter-based DVR. A deep analysis through different diagrams would show the advantages or disadvantages of each compensation method. Equations for all methods are derived, and the characteristics of algorithms are compared with each other.

  8. Comparison between Different Control Strategies of a Z-Source Inverter Based Dynamic Voltage Restorer

    Directory of Open Access Journals (Sweden)

    Abolfazl Kazemdehdashti

    2013-01-01

    Full Text Available In this paper, dynamic voltage restorer (DVR compensation methods are compared to each other for the load side connected shunt converter topology of z-source inverter based DVR to choose the best method. Four different topologies are recognized for DVR that two of them have energy storage devices, and two topologies have no energy storage that take ener\\-gy from the grid during the period of compensation. Here the load side connected shunt converter topology that takes necessary energy from the grid is used. Pre-sag compensation, in-phase compensation, energy-optimized methods are the three DVR compensation methods that studied and compared. A deep analysis through different diagrams would show the advantages or disadvantages of each compensation method. Equations for all methods are derived and the characteristics of algorithms are compared with each other. The simulation results done by SIMULINK/ MATLAB shows compensating by this topology based on the compensation methods.

  9. Improved fault ride through capability of DFIG based wind turbines using synchronous reference frame control based dynamic voltage restorer.

    Science.gov (United States)

    Rini Ann Jerin, A; Kaliannan, Palanisamy; Subramaniam, Umashankar

    2017-09-01

    Fault ride through (FRT) capability in wind turbines to maintain the grid stability during faults has become mandatory with the increasing grid penetration of wind energy. Doubly fed induction generator based wind turbine (DFIG-WT) is the most popularly utilized type of generator but highly susceptible to the voltage disturbances in grid. Dynamic voltage restorer (DVR) based external FRT capability improvement is considered. Since DVR is capable of providing fast voltage sag mitigation during faults and can maintain the nominal operating conditions for DFIG-WT. The effectiveness of the DVR using Synchronous reference frame (SRF) control is investigated for FRT capability in DFIG-WT during both balanced and unbalanced fault conditions. The operation of DVR is confirmed using time-domain simulation in MATLAB/Simulink using 1.5MW DFIG-WT. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  10. A Dynamic Voltage Restorer based on Matrix Converter with Fuzzy Controller

    Directory of Open Access Journals (Sweden)

    Amin Shabanpour

    2012-01-01

    Full Text Available In this paper, a Dynamic Voltage Restorer (DVR without any energy storage devices is proposed to compensate network voltage during disturbances. This DVR utilizes a matrix converter in its topology which eliminates the DC-link capacitor of conventional DVR. The modulation method for matrix converter which is used in this paper is indirect space vector modulation. A fuzzy PI controller is proposed instead of conventional PI controllers. The proposed topology is able to compensate balanced sags/swells as well as unbalanced ones. Moreover it can compensate harmonic pollution of the input source. The simulation results in MATLAB/Simulink environment show that the proposed DVR operates well during different disturbances and it has the ability to control the sensitive load voltage.

  11. A comprehensive review of dynamic voltage restorers

    DEFF Research Database (Denmark)

    Farhadi-Kangarlu, Mohammad; Babaei, Ebrahim; Blaabjerg, Frede

    2017-01-01

    will consider all of the fast voltage compensators, i.e. the devices called Static Series Compensator (SSC), sag corrector, Dynamic Sag Corrector (DySC), and other similar devices are also considered. All of these devices will be called DVR since they operate almost in the same way. Some comparative conclusions......During the last half century the Power Quality (PQ) related problems have become important issues. Many solutions have been proposed to address the PQ problems. The most attractive and flexible way is to use power electronic converter based devices such as Dynamic Voltage Restorer (DVR......), Distribution Static Compensator (DSTATCOM), Unified Power Quality Conditioner (UPQC), Uninterruptible Power Supply (UPS), and other devices usually called custom power devices. Among custom power devices, the DVR is the most economical solution to overcome the voltage-related PQ problems. Intensive research...

  12. Secondary Droop for Frequency and Voltage Restoration in Microgrids

    DEFF Research Database (Denmark)

    Nutkani, Inam Ullah; Peng, Wang; Blaabjerg, Frede

    2015-01-01

    . With the proposed method, the microgrid frequency and voltage can be restored back to nominal value without affecting the power sharing performance of the generation sources. The proposed scheme performance has been validated in simulation for several cases of active and reactive power load conditions.......Droop based autonomous control offers several advantages such as communication independence, plug-n-play capability and enhanced reliability of the system. Despite these advantages, frequency and voltage of droop controlled microgrid varies with the load change which is one of the major drawback...... of the droop control. Presently, the frequency and voltage restoration in microgrid is achieved through secondary control using low bandwidth communication links. This paper presents secondary-droop based frequency and voltage restoration method which is fully autonomous and independent of communication links...

  13. Analysis and Mathematical Model for Restitution of Voltage Using Dynamic Voltage Restorer

    Directory of Open Access Journals (Sweden)

    C. Gopinath

    2014-01-01

    Full Text Available Voltage sag and swell have a major concern in the distribution systems. In order to mitigate the voltage sag and swell, a custom power device called dynamic voltage restorer (DVR is used. The proposed system is a polymer electrolyte membrane (PEM fuel cell based DVR. The energy from the fuel cell is stored in the super capacitor to restitute the voltage. In this proposed DVR, Z-source inverter is used instead of traditional inverter because of buck-boost and shoot through capability. The simulation is performed using three controller topologies: PI controller, synchronous reference frame controller and fuzzy controller and the results are verified using Matlab-Simulink environment.

  14. Design and control of single-phase dynamic voltage restorer

    Indian Academy of Sciences (India)

    Dynamic voltage restorer (DVR) is a custom power device used in electrical distribution system for power quality improvement. It ensures regulated voltage supply to the sensitive loads, even in case of voltage sag and swell disturbances in the distribution network. It is a series connected device and compensates voltagesag ...

  15. A dynamic voltage restorer (DVR) with selective harmonic compensation at medium voltage level

    DEFF Research Database (Denmark)

    Newman, M.J.; Holmes, D.G.; Nielsen, J.G.

    2005-01-01

    Dynamic voltage restorers (DVRs) are now becoming more established in industry to reduce the impact of voltage sags to sensitive loads. However, DVRs spend most of their time in standby mode, since voltage sags occur very infrequently, and hence their utilization is low. In principle, it would...... voltage harmonic compensation capabilities with minimal effect on the sag compensation performance of the basic DVR. The proposed controller has been experimentally verified on a medium-voltage (10 kV) three-phase DVR prototype under a range of conditions, including distorted supply voltages, nonlinear...... loads, and operation during distorted voltage sags....

  16. Design and Control of a Dynamic Voltage Restorer

    DEFF Research Database (Denmark)

    Nielsen, John Godsk

    of the described events can be a potential problem for sensitiv loads. During the thesis knowledge is gathered about power quality and power electronics for voltage quality improvements. In addition knowledge about the design and control of a DVR either connected at the low voltage or the medium voltage level......This thesis is the main results from a Ph.D. project under the research programme "Local Compensation" at Aalborg University. The main topics in the thesis are the design and control of a Dynamic Voltage Restorer (DVR). The DVR is a series connected device, which primarily can protect sensitive...... electric consumers against voltage dips and surges in the medium and low voltage distribution grid. The thesis first gives an introduction to relevant power quality issues for a DVR and power electronic controllers for voltage dip mitigation. Thereafter the operation and the elements in a DVR are described...

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

    Directory of Open Access Journals (Sweden)

    Ahmed M. Saeed

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

  19. A detailed comparison of system topologies for dynamic voltage restorers

    DEFF Research Database (Denmark)

    Nielsen, J.G.; Blaabjerg, Frede

    2005-01-01

    In this paper, four different system topologies for dynamic voltage restorers (DVRs) are analyzed and tested, with particular focus on the methods used to acquire the necessary energy during a voltage sag. Comparisons are made between two topologies that can be realized with a minimum amount...... of energy storage, with energy taken from the grid during the voltage sag, and two topologies that take energy from stored energy devices during the voltage sag. Experimental tests using a 10-kVA DVR show that the no-energy storage concept is feasible, but an improved performance can be achieved for certain...... voltage sags using stored energy topologies. The results of this comparison rank the no-storage topology with a passive shunt converter on the load side first, followed by the stored energy topology with a constant dc-link voltage....

  20. Reduced semiconductor three-level interline dynamic voltage restorer

    DEFF Research Database (Denmark)

    Zhang, Lei; Loh, Poh Chang; Gao, Feng

    2011-01-01

    The previously proposed Interline Dynamic Voltage Restorer (IDVR) system enhances its capability to compensate for long-term and deep voltage sags from propagating to critical loads in power system without requiring a bulky energy storage device. By having multiple DVRs connected to different...... transmission feeders, the common energy storage in IDVR system can be dynamically replenished from an unaffected feeder so as to maintain the rated power of critical loads in another feeder where voltage sag appears. However, despite its enhancement in compensation capability, the drawbacks faced by original...

  1. RETRACTED ARTICLE: Dynamic voltage restorer controller using grade algorithm

    Directory of Open Access Journals (Sweden)

    S. Deepa

    2015-12-01

    Full Text Available This paper deals with the terminology and various issues about power quality problems. This problem occurs owing to voltage sag, swell, harmonics, and surges. The sustained overvoltage and undervoltage originated from power system may often damage/or disrupt computerized process. Voltage sags and harmonics disturb the power quality and this can be overcome by custom power device called dynamic voltage restorer (DVR. The DVR is normally installed between the source voltage and critical or sensitive load. The vital role of DVR depends on the efficiency of the control technique involved in switching circuit of the inverter. In this paper, Combination of improved grade algorithm with fuzzy membership function is used to decide the Proportional-Integral coefficients. The DVR works well both in balanced and unbalanced conditions of voltages. The simulation results show the efficiency of the proposed method.

  2. Power Restoration in Medium Voltage Network Using Multiagent System

    Directory of Open Access Journals (Sweden)

    Miroslav Kovac

    2013-01-01

    Full Text Available The article describes a novel approach to a power restoration in medium voltage power distribution network. It focuses primary at searching of a new network configuration enabling to minimalize the size of faulted area and to restore the power for the highest possible number of loads. It describes characteristic features of medium voltage power distribution network and discusses the implementation of the presented approach in existing networks. A software tool, developed by the authors, including physical simulation of model network and its autonomous control system is described. An example of fault situation in a virtual distribution network is presented. Afterwards, the solution of restoration problem by proposed multiagent system is simulated using the software tool described in the paper.

  3. Modeling and Simulation of Dynamic Voltage Restorer (DVR for Enhancing Voltage Sag

    Directory of Open Access Journals (Sweden)

    Amrita RAI

    2008-01-01

    Full Text Available The aim of this paper is to summaries the fundamental aspects of voltage sag production and their effects on power quality as well as enhancing this power quality in distribution network, using FACTS (Flexible AC Transmission System Devices i.e. Dynamic Voltage Restorer (DVR. DVR is a powerful custom power device for short duration voltage compensation, which is connected in series with the load & hence it possesses some advantages. (In this paper detailed modeling and simulation and analysis of the DVR device is presented.

  4. Control and Testing of a Dynamic Voltage Restorer (DVR) at Medium Voltage Level

    DEFF Research Database (Denmark)

    Nielsen, John Godsk; Newman, Michael; Nielsen, Hans Ove

    2004-01-01

    The dynamic voltage restorer (DVR) has become popular as a cost effective solution for the protection of sensitive loads from voltage sags. Implementations of the DVR have been proposed at both a low voltage (LV) level, as well as a medium voltage (MV) level; and give an opportunity to protect high...... power sensitive loads from voltage sags. This paper reports practical test results obtained on a medium voltage (10 kV) level using a DVR at a Distribution test facility in Kyndby, Denmark. The DVR was designed to protect a 400-kVA load from a 0.5-p.u. maximum voltage sag. The reported DVR verifies...... duration voltage sags were created using a controllable LV breaker fed by a 630 kVA Distribution transformer placed upstream of the sensitive load. The fault currents in excess of 12 kA were designed and created to obtain the required voltage sags. It is concluded the DVR works well in all operating...

  5. Voltage harmonic elimination with RLC based interface smoothing filter

    Science.gov (United States)

    Chandrasekaran, K.; Ramachandaramurthy, V. K.

    2015-04-01

    A method is proposed for designing a Dynamic Voltage Restorer (DVR) with RLC interface smoothing filter. The RLC filter connected between the IGBT based Voltage Source Inverter (VSI) is attempted to eliminate voltage harmonics in the busbar voltage and switching harmonics from VSI by producing a PWM controlled harmonic voltage. In this method, the DVR or series active filter produces PWM voltage that cancels the existing harmonic voltage due to any harmonic voltage source. The proposed method is valid for any distorted busbar voltage. The operating VSI handles no active power but only harmonic power. The DVR is able to suppress the lower order switching harmonics generated by the IGBT based VSI. Good dynamic and transient results obtained. The Total Harmonic Distortion (THD) is minimized to zero at the sensitive load end. Digital simulations are carried out using PSCAD/EMTDC to validate the performance of RLC filter. Simulated results are presented.

  6. An Improved Droop Control Method for DC Microgrids Based on Low Bandwidth Communication with DC Bus Voltage Restoration and Enhanced Current Sharing Accuracy

    DEFF Research Database (Denmark)

    Lu, Xiaonan; Guerrero, Josep M.; Sun, Kai

    2014-01-01

    of the dc microgrid operation, a low bandwidth communication (LBC) based improved droop control method is proposed. In contrast with the conventional approach, the control system does not require a centralized secondary controller. Instead, it uses local controllers and the LBC network to exchange......, and the LBC system is only used for changing the values of the dc voltage and current. Hence, a decentralized control scheme is accomplished. The simulation test based on Matlab/Simulink and the experimental validation based on a 2×2.2 kW prototype were implemented to demonstrate the proposed approach....

  7. A Novel Three-Phase Three-Wire Dynamic Voltage Restorer

    Science.gov (United States)

    Zhou, W. P.; Wang, Z. Y.; Wu, Z. G.

    2017-10-01

    A novel optimal control method of three-phase three-wire Dynamic Voltage Restorer (DVR) and its simplified topological structure are proposed. Based on virtual-floating-ground analysis method, a time-domain mathematical model and the control equation of DVR’s converter are established; the optimal feasible solution with minimum objective function value of the control equation is deduced. Compensation voltage detection is based on digital phase lock, and the switching time is calculated by line voltages, the control performance under the proposed control strategy is analyzed, which greatly improve the utilization rate of DC side voltage and the DVR’s compensation capability. The simulation and experiment results of three-phase three-wire DVR under the proposed algorithm are given; the results show its validity and feasibility.

  8. Improving Low Voltage Ride Through Capability of Wind Generators Using Dynamic Voltage Restorer

    Science.gov (United States)

    Sivasankar, Gangatharan; Suresh Kumar, Velu

    2014-08-01

    The increasing wind power integration with power grid has forced the situation to improve the reliability of wind generators for stable operation. One important problem with induction generator based wind farm is its low ride through capability to the grid voltage disturbance. Any disturbance such as voltage dip may cause wind farm outages. Since wind power contribution is in predominant percentage, such outages may lead to stability problem. The proposed strategy is to use dynamic voltage controller (DVR) to compensate the voltage disturbance. The DVR provides the wind generator the ability to remain connected in grid and improve the reliability. The voltage dips due to symmetrical and unsymmetrical faults are considered for analysis. The vector control scheme is employed for fault compensation which uses software phase locked loop scheme and park dq0 transformation technique. Extensive simulation results are included to illustrate the control and operation of DVR.

  9. Preparation of Power Distribution System for High Penetration of Renewable Energy Part I. Dynamic Voltage Restorer for Voltage Regulation Pat II. Distribution Circuit Modeling and Validation

    Science.gov (United States)

    Khoshkbar Sadigh, Arash

    Part I: Dynamic Voltage Restorer In the present power grids, voltage sags are recognized as a serious threat and a frequently occurring power-quality problem and have costly consequence such as sensitive loads tripping and production loss. Consequently, the demand for high power quality and voltage stability becomes a pressing issue. Dynamic voltage restorer (DVR), as a custom power device, is more effective and direct solutions for "restoring" the quality of voltage at its load-side terminals when the quality of voltage at its source-side terminals is disturbed. In the first part of this thesis, a DVR configuration with no need of bulky dc link capacitor or energy storage is proposed. This fact causes to reduce the size of the DVR and increase the reliability of the circuit. In addition, the proposed DVR topology is based on high-frequency isolation transformer resulting in the size reduction of transformer. The proposed DVR circuit, which is suitable for both low- and medium-voltage applications, is based on dc-ac converters connected in series to split the main dc link between the inputs of dc-ac converters. This feature makes it possible to use modular dc-ac converters and utilize low-voltage components in these converters whenever it is required to use DVR in medium-voltage application. The proposed configuration is tested under different conditions of load power factor and grid voltage harmonic. It has been shown that proposed DVR can compensate the voltage sag effectively and protect the sensitive loads. Following the proposition of the DVR topology, a fundamental voltage amplitude detection method which is applicable in both single/three-phase systems for DVR applications is proposed. The advantages of proposed method include application in distorted power grid with no need of any low-pass filter, precise and reliable detection, simple computation and implementation without using a phased locked loop and lookup table. The proposed method has been verified

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

    Science.gov (United States)

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

    2015-10-01

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

  11. Design and control of single-phase dynamic voltage restorer

    Indian Academy of Sciences (India)

    Amit Meena

    ventionally, DVR consists of an energy storage device, which supplies the required power over the limited duration of the sags. Large magnitude and long duration of sags lead to heavy financial investment in energy storage unit. To overcome this limitation, a single-phase back-to-back converter-based DVR is implemented ...

  12. Cascode-based voltage-amplifier stage

    Directory of Open Access Journals (Sweden)

    Pospisilik Martin

    2017-01-01

    Full Text Available Voltage-amplifier stages are the basic components of commonly used high gain amplifiers the bias and other parameters of whose are set by the external negative feedback. The typical device that uses the voltage-amplifier stage is the operational amplifier. Similar constructions can also be created on the basis of discrete transistors. From the circuit designer’s point of view, the voltage-amplifier stage defines the crucial parameters of the whole unit - the amplification factor, dominant pole of its transfer function and the slew rate. In this paper the proposal on construction of the voltage-amplifier stage based on discrete transistors is described. When connected between the input differential amplifier and the output stage, it allows creating of cheap amplifier for HiFi applications with considerable performance.

  13. Sliding Mode Control of Dynamic Voltage Restorer by Using a New Adaptive Reaching Law

    Science.gov (United States)

    Pandey, Achala; Agrawal, Rekha; Mandloi, Ravindra S.; Sarkar, Biswaroop

    2017-08-01

    This paper presents a new kind of adaptive reaching law for sliding mode control of Dynamic Voltage Restorer (DVR). Such an adaptive reaching law follows under-damped sinusoidal nature that causes the initial state to reach the sliding regime in extremely less time with negligible chattering. Moreover, it is robust in the sense the trajectory does not deviate from the sliding surface. This new approach is developed and successfully applied to DVR. The simulation results are presented that show its robustness.

  14. CNFET Based Voltage Differencing Transconductance Amplifier

    Science.gov (United States)

    Laxya; Prasad, Dinesh; Mainuddin; Islam, S. S.

    2017-08-01

    In CMOS Technology basic Problem mainly includes dopant fluctuation, tunnelling effect and line edge roughness below 45nm technology. Carbon Nanotube based structures is better option for widen the Moore’s law due to its scalability channel electrostatics and higher mobility. In this manuscript we demonstrate an optimum design for linear property of CNTFET based VDTA at 32nm technology node. The proposed circuit consist of VDTA with CNTFET having two voltage input and two current outputs so that it works as voltage and transconductance operation to obtain the high performance. The minimum supply voltages of ±0.9V with 32nm technology mode are used. The CNTFET-VDTA performance is simulated on HSPICE. In this paper CNFET-based VDTA provides better results of DC transfer characteristics as compared with CMOS. All the simulation results are performed on HSPICE.

  15. Restorative Justice as Strength-Based Accountability

    Science.gov (United States)

    Ball, Robert

    2003-01-01

    This article compares strength-based and restorative justice philosophies for young people and their families. Restorative justice provides ways to respond to crime and harm that establish accountability while seeking to reconcile members of a community. Restorative approaches are an important subset of strength-based interventions.

  16. voltage compensation using artificial neural network

    African Journals Online (AJOL)

    Offor Theophilos

    VOLTAGE COMPENSATION USING ARTIFICIAL NEURAL NETWORK: A CASE STUDY OF. RUMUOLA ... using artificial neural network (ANN) controller based dynamic voltage restorer (DVR). ... substation by simulating with sample of average voltage for Omerelu, Waterlines, Rumuola, Shell Industrial and Barracks.

  17. Voltage Sag Source Location Based on Instantaneous Energy Detection

    DEFF Research Database (Denmark)

    Chen, Zhe; Kong, Wei; Dong, Xinzhou

    2008-01-01

    Voltage sag is a major power quality problem, which could disrupt the operation of voltage-sensitive equipment. This paper presents the method based on variation components-based instantaneous energy for voltage sag source detection. Simulations have been performed to provide the thorough analysis...... for system with distributed generation units. The studies show that the presented method can effectively detect the location of voltage sag source....

  18. ROV based underwater blurred image restoration

    Science.gov (United States)

    Zhishen, Liu; Tianfu, Ding; Gang, Wang

    2003-04-01

    In this paper, we present a method of ROV based image processing to restore underwater blurry images from the theory of light and image transmission in the sea. Computer is used to simulate the maximum detection range of the ROV under different water body conditions. The receiving irradiance of the video camera at different detection ranges is also calculated. The ROV’s detection performance under different water body conditions is given by simulation. We restore the underwater blurry images using the Wiener filter based on the simulation. The Wiener filter is shown to be a simple useful method for underwater image restoration in the ROV underwater experiments. We also present examples of restored images of an underwater standard target taken by the video camera in these experiments.

  19. LED-Based High-Voltage Lines Warning System

    Directory of Open Access Journals (Sweden)

    Eldar MUSA

    2013-04-01

    Full Text Available LED-based system, running with the current of high-voltage lines and converting the current flowing through the line into the light by using a toroid transformer, has been developed. The transformer’s primary winding is constituted by the high voltage power line. Toroidal core consists of two equal parts and the secondary windings are evenly placed on these two parts. The system is mounted on the high-voltage lines as a clamp. The secondary winding ends are connected in series by the connector on the clamp. LEDs are supplied by the voltage at the ends of secondary. Current flowing through highvoltage transmission lines is converted to voltage by the toroidal transformer and the light emitting LEDs are supplied with this voltage. The theory of the conversion of the current flowing through the line into the light is given. The system, running with the current of the line and converting the current into the light, has been developed. System has many application areas such as warning high voltage lines (warning winches to not hinder the high-voltage lines when working under the lines, warning planes to not touch the high-voltage lines, remote measurement of high-voltage line currents, and local illumination of the line area

  20. On-Line Voltage Stability Assessment based on PMU Measurements

    DEFF Research Database (Denmark)

    Garcia-Valle, Rodrigo; P. Da Silva, Luiz C.; Nielsen, Arne Hejde

    2009-01-01

    through statistic analysis. During the off-line analysis, a memory of high-risk situations following a pre-defined voltage stability criterion is obtained. Thereafter, basic statistics analyses are applied resulting in the definition of voltage regions. During on-line operation, voltage magnitudes...... of critical buses obtained by phasor measurements are monitored in relation to the risk regions. Comprehensive studies demonstrate that the proposed method could assist operators to avoid voltage collapse events, by taking preventive or emergency actions.......This paper presents a method for on-line monitoring of risk voltage collapse based on synchronised phasor measurement. As there is no room for intensive computation and analysis in real-time, the method is based on the combination of off-line computation and on-line monitoring, which are correlated...

  1. Voltage Mode Single CDBA Based Multifunction Filter

    Science.gov (United States)

    Gupta, Priyanka; Pandey, Rajeshwari; Pandey, Neeta

    2017-08-01

    A voltage mode multifunction second order filter topology employing single current differencing buffered amplifier (CDBA) has been proposed in this paper. This topology can be used to synthesize low pass (LP), band pass (BP), and high pass (HP) filter functions with appropriate admittance choices. This configuration is a suitable choice for implementing filters with high quality factor. The demonstration of the proposed configuration is done through PSPICE simulations. The CDBA block is realized using CMOS 0.18µm technology. The simulation results are found in close agreement with the theoretical results.

  2. PV source based high voltage gain current fed converter

    Science.gov (United States)

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

    2017-11-01

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

  3. Ac Synchronous Servo Based On The Armature Voltage Prediction Model

    Science.gov (United States)

    Hoshino, Akihiro; Kuromaru, Hiroshi; Kobayashi, Shinichi

    1987-10-01

    A new control method of the AC synchro-nous servo-system (Brushless DC servo-system) is discussed. The new system is based on the armature voltage prediction model. Without a resolver-digital-conver-ter nor a tachometer-generator, the resolver provides following three signals to the system immediately, they are the current command, the induced voltage, and the rotor speed. The new method realizes a simple hardware configuration. Experimental results show a good performance of the system.

  4. OFCC based voltage and transadmittance mode instrumentation amplifier

    Science.gov (United States)

    Nand, Deva; Pandey, Neeta; Pandey, Rajeshwari; Tripathi, Prateek; Gola, Prashant

    2017-07-01

    The operational floating current conveyor (OFCC) is a versatile active block due to the availability of both low and high input and output impedance terminals. This paper addresses the realization of OFCC based voltage and transadmittance mode instrumentation amplifiers (VMIA and TAM IA). It employs three OFCCs and seven resistors. The transadmittance mode operation can easily be obtained by simply connecting an OFCC based voltage to current converter at the output. The effect of non-idealities of OFCC, in particular finite transimpedance and tracking error, on system performance is also dealt with and corresponding mathematical expressions are derived. The functional verification is performed through SPICE simulation using CMOS based implementation of OFCC.

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

    Directory of Open Access Journals (Sweden)

    Singh Moirangthem Deben

    2015-01-01

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

  6. Voltage Based Detection Method for High Impedance Fault in a Distribution System

    Science.gov (United States)

    Thomas, Mini Shaji; Bhaskar, Namrata; Prakash, Anupama

    2016-09-01

    High-impedance faults (HIFs) on distribution feeders cannot be detected by conventional protection schemes, as HIFs are characterized by their low fault current level and waveform distortion due to the nonlinearity of the ground return path. This paper proposes a method to identify the HIFs in distribution system and isolate the faulty section, to reduce downtime. This method is based on voltage measurements along the distribution feeder and utilizes the sequence components of the voltages. Three models of high impedance faults have been considered and source side and load side breaking of the conductor have been studied in this work to capture a wide range of scenarios. The effect of neutral grounding of the source side transformer is also accounted in this study. The results show that the algorithm detects the HIFs accurately and rapidly. Thus, the faulty section can be isolated and service can be restored to the rest of the consumers.

  7. Synchrophasor-Based Online Coherency Identification in Voltage Stability Assessment

    Directory of Open Access Journals (Sweden)

    ADEWOLE, A. C.

    2015-11-01

    Full Text Available This paper presents and investigates a new measurement-based approach in the identification of coherent groups in load buses and synchronous generators for voltage stability assessment application in large interconnected power systems. A hybrid Calinski-Harabasz criterion and k-means clustering algorithm is developed for the determination of the cluster groups in the system. The proposed method is successfully validated by using the New England 39-bus test system. Also, the performance of the voltage stability assessment algorithm using wide area synchrophasor measurements from the key synchronous generator in each respective cluster was tested online for the prediction of the system's margin to voltage collapse using a testbed comprising of a Programmable Logic Controller (PLC in a hardware-in-the-loop configuration with the Real-Time Digital Simulator (RTDS and Phasor Measurement Units (PMUs.

  8. Genetic algorithm based reactive power dispatch for voltage stability improvement

    Energy Technology Data Exchange (ETDEWEB)

    Devaraj, D. [Department of Electrical and Electronics, Kalasalingam University, Krishnankoil 626 190 (India); Roselyn, J. Preetha [Department of Electrical and Electronics, SRM University, Kattankulathur 603 203, Chennai (India)

    2010-12-15

    Voltage stability assessment and control form the core function in a modern energy control centre. This paper presents an improved Genetic algorithm (GA) approach for voltage stability enhancement. The proposed technique is based on the minimization of the maximum of L-indices of load buses. Generator voltages, switchable VAR sources and transformer tap changers are used as optimization variables of this problem. The proposed approach permits the optimization variables to be represented in their natural form in the genetic population. For effective genetic processing, the crossover and mutation operators which can directly deal with the floating point numbers and integers are used. The proposed algorithm has been tested on IEEE 30-bus and IEEE 57-bus test systems and successful results have been obtained. (author)

  9. Low voltage varistor ceramics based on SnO2

    Indian Academy of Sciences (India)

    WINTEC

    Low voltage varistor ceramics based on SnO2. S R DHAGE*, V RAVI. † and O B YANG. School of Environmental and Chemical Engineering, Chonbuk National University, Jeonju 561-756, South Korea. †. Physical and Materials Chemistry Division, National Chemical Laboratory, Pune 411 008, India. MS received 21 May ...

  10. Mitigation of Voltage Sags in CIGRE Low Voltage Distribution Network

    DEFF Research Database (Denmark)

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

    2013-01-01

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

  11. Low voltage organic permeable base N-type transistor

    Science.gov (United States)

    Agrawal, Kalpana; Rana, Omwati; Singh, Nidhi; Srivastava, Ritu; Rajput, S. S.

    2016-10-01

    A vertical n-type organic permeable metal base transistor was fabricated using N,N-ditridecylperylene-3,4,9,10-tetracarboxylic diimide as an active material for making emitter and collector regions. A composite of Al//C60/Al/AlOx forms the base region of the proposed structure. The detailed study of the Early effect was carried out for determining the intrinsic gain, transconductance, and output impedance which were found to be 92, 145 μΩ-1, and 0.634 MΩ, respectively, at an applied bias of 1 V between collector-emitter contacts. The device is capable of operating at a low voltage of 1 V, which makes it suitable for low voltage and high frequency applications.

  12. Inverter-based circuit design techniques for low supply voltages

    CERN Document Server

    Palani, Rakesh Kumar

    2017-01-01

    This book describes intuitive analog design approaches using digital inverters, providing filter architectures and circuit techniques enabling high performance analog circuit design. The authors provide process, supply voltage and temperature (PVT) variation-tolerant design techniques for inverter based circuits. They also discuss various analog design techniques for lower technology nodes and lower power supply, which can be used for designing high performance systems-on-chip.    .

  13. Restoration in multi-domain GMPLS-based networks

    DEFF Research Database (Denmark)

    Manolova, Anna; Ruepp, Sarah Renée; Dittmann, Lars

    2011-01-01

    In this paper, we evaluate the efficiency of using restoration mechanisms in a dynamic multi-domain GMPLS network. Major challenges and solutions are introduced and two well-known restoration schemes (End-to-End and Local-to-End) are evaluated. Additionally, new restoration mechanisms...... are introduced: one based on the position of a failed link, called Location-Based, and another based on minimizing the additional resources consumed during restoration, called Shortest-New. A complete set of simulations in different network scenarios show where each mechanism is more efficient in terms, such as...

  14. Image Restoration Technology Based on Discrete Neural network

    Directory of Open Access Journals (Sweden)

    Zhou Duoying

    2015-01-01

    Full Text Available With the development of computer science and technology, the development of artificial intelligence advances rapidly in the field of image restoration. Based on the MATLAB platform, this paper constructs a kind of image restoration technology of artificial intelligence based on the discrete neural network and feedforward network, and carries out simulation and contrast of the restoration process by the use of the bionic algorithm. Through the application of simulation restoration technology, this paper verifies that the discrete neural network has a good convergence and identification capability in the image restoration technology with a better effect than that of the feedforward network. The restoration technology based on the discrete neural network can provide a reliable mathematical model for this field.

  15. Incentive-Based Voltage Regulation in Distribution Networks

    Energy Technology Data Exchange (ETDEWEB)

    Dall-Anese, Emiliano [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Baker, Kyri A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zhou, Xinyang [University of Colorado; Chen, Lijun [University of Colorado

    2017-07-03

    This paper considers distribution networks fea- turing distributed energy resources, and designs incentive-based mechanisms that allow the network operator and end-customers to pursue given operational and economic objectives, while concurrently ensuring that voltages are within prescribed limits. Two different network-customer coordination mechanisms that require different amounts of information shared between the network operator and end-customers are developed to identify a solution of a well-defined social-welfare maximization prob- lem. Notably, the signals broadcast by the network operator assume the connotation of prices/incentives that induce the end- customers to adjust the generated/consumed powers in order to avoid the violation of the voltage constraints. Stability of the proposed schemes is analytically established and numerically corroborated.

  16. Heuristic Based Approach for Voltage Stability Improvement using FACTS Devices

    Directory of Open Access Journals (Sweden)

    Hajer Jmii

    2017-12-01

    Full Text Available The aim of this paper is to develop a hybrid device for voltage stability enhancement using two kinds of FACTS (Flexible AC Transmission System namely SVC (Static Var Compensator and TCSC (Thyristor Controlled Series Capacitor. The idea behind the proposed method is to maintain safe and satisfactory power system operation in a lesser costing manner by taking advantage of the performances of SVC and TCSC at the same time. We propose to evaluate the efficacy of the combined device to UPFC, as it is a hybrid FACTS and it is the most versatile compensator. For purpose of identifying the placement of the devices, we opt for a heuristic based approach. The methodology is tested with the IEEE 14-Bus system using the software EUROSTAG, and the simulation results reveal the efficiency of the proposed method for enhancing voltage stability.

  17. Incentive-Based Voltage Regulation in Distribution Networks: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Xinyang; Chen, Lijun; Dall' Anese, Emiliano; Baker, Kyri

    2017-03-03

    This paper considers distribution networks fea- turing distributed energy resources, and designs incentive-based mechanisms that allow the network operator and end-customers to pursue given operational and economic objectives, while concurrently ensuring that voltages are within prescribed limits. Two different network-customer coordination mechanisms that require different amounts of information shared between the network operator and end-customers are developed to identify a solution of a well-defined social-welfare maximization prob- lem. Notably, the signals broadcast by the network operator assume the connotation of prices/incentives that induce the end- customers to adjust the generated/consumed powers in order to avoid the violation of the voltage constraints. Stability of the proposed schemes is analytically established and numerically corroborated.

  18. Droplet Demulsification Using Ultralow Voltage-Based Electrocoalescence.

    Science.gov (United States)

    Srivastava, A; Karthick, S; Jayaprakash, K S; Sen, A K

    2018-01-30

    Demulsification of droplets stabilized with surfactant is very challenging due to their low surface energy. We report ultralow voltage-based electrocoalescence phenomenon for the demulsification of aqueous droplets with an aqueous stream. In the absence of electric field, due to the disjoining pressure resulting from the tail-tail interaction between the surfactant molecules present on the aqueous droplets and interface, coalescence of aqueous droplets with the aqueous stream is prevented. However, above a critical electric field, the electrical stress overcomes the disjoining pressure, thus leading to the droplet coalescence. The influence of surfactant concentration, droplet diameter, and velocity on the electrocoalescence phenomena is studied. The macroscopic contact between the aqueous droplet with the aqueous stream enables droplet coalescence at much lower voltage (10 to 90 V), which is at least two orders of magnitude smaller than voltages used in prior works (1.0 to 3.0 kV). The electrocoalescence phenomena is used for the extraction of microparticles encapsulated in aqueous droplets into the aqueous stream and size-based selective demulsification. A new paradigm of droplet electrocoalescence and content extraction is presented that would find significant applications in chemistry and biology.

  19. Models for Patch-Based Image Restoration

    Directory of Open Access Journals (Sweden)

    Mithun Das Gupta

    2009-01-01

    Full Text Available We present a supervised learning approach for object-category specific restoration, recognition, and segmentation of images which are blurred using an unknown kernel. The novelty of this work is a multilayer graphical model which unifies the low-level vision task of restoration and the high-level vision task of recognition in a cooperative framework. The graphical model is an interconnected two-layer Markov random field. The restoration layer accounts for the compatibility between sharp and blurred images and models the association between adjacent patches in the sharp image. The recognition layer encodes the entity class and its location in the underlying scene. The potentials are represented using nonparametric kernel densities and are learnt from training data. Inference is performed using nonparametric belief propagation. Experiments demonstrate the effectiveness of our model for the restoration and recognition of blurred license plates as well as face images.

  20. Models for Patch-Based Image Restoration

    Directory of Open Access Journals (Sweden)

    Petrovic Nemanja

    2009-01-01

    Full Text Available Abstract We present a supervised learning approach for object-category specific restoration, recognition, and segmentation of images which are blurred using an unknown kernel. The novelty of this work is a multilayer graphical model which unifies the low-level vision task of restoration and the high-level vision task of recognition in a cooperative framework. The graphical model is an interconnected two-layer Markov random field. The restoration layer accounts for the compatibility between sharp and blurred images and models the association between adjacent patches in the sharp image. The recognition layer encodes the entity class and its location in the underlying scene. The potentials are represented using nonparametric kernel densities and are learnt from training data. Inference is performed using nonparametric belief propagation. Experiments demonstrate the effectiveness of our model for the restoration and recognition of blurred license plates as well as face images.

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

    OpenAIRE

    Wang, Yun; Wu, Qiuwei; Gong, Wenming; Gryning, Mikkel Peter Sidoroff

    2016-01-01

    This paper proposes an H∞ robust current controller for doubly fed induction generator (DFIG) based wind turbines (WTs) subject to grid voltage distortions. The controller is to mitigate the impact of the grid voltage distortions on rotor currents with DFIG parameter perturbation. The grid voltage distortions considered include asymmetric voltage dips and grid background harmonics. An uncertain DFIG model is developed with uncertain factors originating from distorted stator voltage, and chang...

  2. An estimator-based distributed voltage-predictive control strategy for ac islanded microgrids

    DEFF Research Database (Denmark)

    Wang, Yanbo; Chen, Zhe; Wang, Xiongfei

    2015-01-01

    distributed generator, where the voltage estimator serves as an essential tool to obtain network voltages response without using communication links, while the voltage predictive controller is able to implement offset-free voltage control for a specified bus. The dynamic performance of the proposed voltage......This paper presents an estimator-based voltage predictive control strategy for AC islanded microgrids, which is able to perform voltage control without any communication facilities. The proposed control strategy is composed of a network voltage estimator and a voltage predictive controller for each...... perturbation, load parameters variation, different disturbance locations, LC filters perturbation, output impedances perturbation and DG unit fault. The simulation and experimental results show that the proposed control approach is able to perform offset-free voltage control without any communication links...

  3. Restoration of motion-blurred image based on border deformation detection: a traffic sign restoration model.

    Directory of Open Access Journals (Sweden)

    Yiliang Zeng

    Full Text Available Due to the rapid development of motor vehicle Driver Assistance Systems (DAS, the safety problems associated with automatic driving have become a hot issue in Intelligent Transportation. The traffic sign is one of the most important tools used to reinforce traffic rules. However, traffic sign image degradation based on computer vision is unavoidable during the vehicle movement process. In order to quickly and accurately recognize traffic signs in motion-blurred images in DAS, a new image restoration algorithm based on border deformation detection in the spatial domain is proposed in this paper. The border of a traffic sign is extracted using color information, and then the width of the border is measured in all directions. According to the width measured and the corresponding direction, both the motion direction and scale of the image can be confirmed, and this information can be used to restore the motion-blurred image. Finally, a gray mean grads (GMG ratio is presented to evaluate the image restoration quality. Compared to the traditional restoration approach which is based on the blind deconvolution method and Lucy-Richardson method, our method can greatly restore motion blurred images and improve the correct recognition rate. Our experiments show that the proposed method is able to restore traffic sign information accurately and efficiently.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-12-13

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

  5. Improved Active Harmonic Current Elimination Based on Voltage Detection.

    Directory of Open Access Journals (Sweden)

    Tianyuan Tan

    Full Text Available With the increasing penetration of power electronic equipment in modern residential distribution systems, harmonics mitigation through the distributed generation (DG interfacing converters has received significant attention. Among recently proposed methods, the so-called active resonance damper (ARD and harmonic voltage compensator (HVC based on voltage detection can effectively reduce the harmonic distortions in selected areas of distribution systems. However, it is found out that when traditional ARD algorithm is used to eliminate harmonic current injected by non-linear loads, its performance is constrained by stability problems and can at most eliminate half of the load harmonic currents. Thus, inspired by the duality between ARD and HVC, this paper presents a novel improved resistive active power filter (R-APF algorithm based on integral-decoupling control. The design guideline for its parameters is then investigated through carefully analyzing the closed-loop poles' trajectory. Computer studies demonstrate that the proposed algorithm can effectively mitigate the load harmonic currents and its performance is much better than traditional ARD based on proportional control.

  6. Improved Active Harmonic Current Elimination Based on Voltage Detection

    Science.gov (United States)

    Tan, Tianyuan; Dong, Shuan; Huang, Yingwei; Liu, Jian; Le, Jian; Liu, Kaipei

    2016-01-01

    With the increasing penetration of power electronic equipment in modern residential distribution systems, harmonics mitigation through the distributed generation (DG) interfacing converters has received significant attention. Among recently proposed methods, the so-called active resonance damper (ARD) and harmonic voltage compensator (HVC) based on voltage detection can effectively reduce the harmonic distortions in selected areas of distribution systems. However, it is found out that when traditional ARD algorithm is used to eliminate harmonic current injected by non-linear loads, its performance is constrained by stability problems and can at most eliminate half of the load harmonic currents. Thus, inspired by the duality between ARD and HVC, this paper presents a novel improved resistive active power filter (R-APF) algorithm based on integral-decoupling control. The design guideline for its parameters is then investigated through carefully analyzing the closed-loop poles’ trajectory. Computer studies demonstrate that the proposed algorithm can effectively mitigate the load harmonic currents and its performance is much better than traditional ARD based on proportional control. PMID:27295213

  7. Single base mismatch detection by microsecond voltage pulses.

    Science.gov (United States)

    Fixe, F; Chu, V; Prazeres, D M F; Conde, J P

    2005-12-15

    A single square voltage pulse applied to metal electrodes underneath a silicon dioxide film upon which DNA probes are immobilized allows the discrimination of DNA targets with a single base mismatch during hybridization. Pulse duration, magnitude and slew rate of the voltage pulse are all key factors controlling the rates of electric field assisted hybridization. Although pulses with 1 V, lasting less than 1 ms and with a rise/fall times of 4.5 ns led to maximum hybridization of fully complementary strands, lack of stringency did not allow the discrimination of single base mismatches. However, by choosing pulse conditions that are slightly off the optimum, the selectivity for discriminating single base mismatches could be improved up to a factor approximately 5 when the mismatch was in the middle of the strand and up to approximately 1.5 when the mismatch was on the 5'-end and. These results demonstrate that hybridization with the appropriate electric field pulse provides a new, site-specific, approach to the discrimination of single nucleotide polymorphisms in the sub-millisecond time scale, for addressable DNA microarrays.

  8. Voltage sag source location based on instantaneous energy detection

    DEFF Research Database (Denmark)

    Chen, Zhe; Xinzhou, Dong; Wei, Kong

    2007-01-01

    Voltage sag is the major power quality problem, which could disrupt the operation of sensitive equipment. This paper presents the applications of instantaneous energy direction for voltage sag source detection. Simulations have been performed to provide the analysis for system with distributed...... generation units. The studies show that the presented method can effectively detect the location of the voltage sag source....

  9. Voltage Stabilizer Based on SPWM technique Using Microcontroller

    Directory of Open Access Journals (Sweden)

    K. N. Tarchanidis

    2013-01-01

    Full Text Available This paper presents an application of the well known SPWM technique on a voltage stabilizer, using a microcontroller. The stabilizer is AC/DC/AC type. So, the system rectifies the input AC voltage to a suitable DC level and the intelligent control of an embedded microcontroller regulates the pulse width of the output voltage in order to produce through a filter a perfect sinusoidal AC voltage. The control program on the microcontroller has the ability to change the FET transistor firing in order to compensate any input voltage variation. The applied software using the microcontroller’s interrupts managed to achieve concurrency on the running program.

  10. A Function-Based Framework for Stream Assessment & Restoration Projects

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Developed by the U.S. Environmental Protection Agency (EPA) and affiliates for approaching stream assessment and restoration from a function-based perspective. May...

  11. A set theoretic approach to object-based image restoration

    Science.gov (United States)

    Fan, Xin; Huang, Hua; Qi, Chun; Liang, Dequn

    2005-03-01

    The approaches that analyze local characteristics of an image to impose constraints are prevailing in image restoration, but they are less effective in the cases of severe degradation and heavy noise corruption. In this paper, we incorporate the common characteristics that the images of a class of objects present into image restoration, termed as object-based image restoration. The characteristics are represented as deterministic sets, which is combined with the set describing the image degradation model in a set theoretic formulation. A parallel subgradient projection algorithm is applied to find the solution in the intersection of these sets. Experiments performed on frontal face images show the improved performance of the approach in both mentioned cases, by comparing with local analysis based algorithms. With the concise formulation and the efficient algorithm, the object-based restoration can be implemented with ease and resolved with less complexity.

  12. Optimal placement of unified power flow controllers to improve dynamic voltage stability using power system variable based voltage stability indices.

    Science.gov (United States)

    Albatsh, Fadi M; Ahmad, Shameem; Mekhilef, Saad; Mokhlis, Hazlie; Hassan, M A

    2015-01-01

    This study examines a new approach to selecting the locations of unified power flow controllers (UPFCs) in power system networks based on a dynamic analysis of voltage stability. Power system voltage stability indices (VSIs) including the line stability index (LQP), the voltage collapse proximity indicator (VCPI), and the line stability index (Lmn) are employed to identify the most suitable locations in the system for UPFCs. In this study, the locations of the UPFCs are identified by dynamically varying the loads across all of the load buses to represent actual power system conditions. Simulations were conducted in a power system computer-aided design (PSCAD) software using the IEEE 14-bus and 39- bus benchmark power system models. The simulation results demonstrate the effectiveness of the proposed method. When the UPFCs are placed in the locations obtained with the new approach, the voltage stability improves. A comparison of the steady-state VSIs resulting from the UPFCs placed in the locations obtained with the new approach and with particle swarm optimization (PSO) and differential evolution (DE), which are static methods, is presented. In all cases, the UPFC locations given by the proposed approach result in better voltage stability than those obtained with the other approaches.

  13. Bulk Restoration for SDN-Based Transport Network

    Directory of Open Access Journals (Sweden)

    Yang Zhao

    2016-01-01

    Full Text Available We propose a bulk restoration scheme for software defined networking- (SDN- based transport network. To enhance the network survivability and improve the throughput, we allow disrupted flows to be recovered synchronously in dynamic order. In addition backup paths are scheduled globally by applying the principles of load balance. We model the bulk restoration problem using a mixed integer linear programming (MILP formulation. Then, a heuristic algorithm is devised. The proposed algorithm is verified by simulation and the results are analyzed comparing with sequential restoration schemes.

  14. A generalized discontinuous PWM based neutral point voltage balancing method for three-level NPC voltage source inverter with switching losses reduction

    DEFF Research Database (Denmark)

    Li, Kai; Wei, Min; Xie, Chuan

    2017-01-01

    In order to control the neutral point voltage of inverter with discontinuous PWM (DPWM), this paper proposed a generalized discontinuous PWM (GDPWM) based neutral point voltage balancing method for three level neutral point clamped (NPC) voltage source inverter (VSI). Firstly, a triangle carrier ...

  15. Identifying Challenges to Building an Evidence Base for Restoration Practice

    Directory of Open Access Journals (Sweden)

    Phumza Ntshotsho

    2015-11-01

    Full Text Available Global acknowledgement of ecological restoration, as an important tool to complement conservation efforts, requires an effort to increase the effectiveness of restoration interventions. Evidence-based practice is purported to promote effectiveness. A central tenet of this approach is decision making that is based on evidence, not intuition. Evidence can be generated experimentally and in practice but needs to be linked to baseline information collection, clear goals and monitoring of impact. In this paper, we report on a survey conducted to assess practitioners’ perceptions of the evidence generated in restoration practice in South Africa, as well as challenges encountered in building this evidence base. Contrary to a recent assessment of this evidence base which found weaknesses, respondents viewed it as adequate and cited few obstacles to its development. Obstacles cited were mostly associated with planning and resource availability. We suggest that the disparity between practitioners’ perceptions and observed weaknesses in the evidence base could be a challenge in advancing evidence-based restoration. We explore opportunities to overcome this disparity as well as the obstacles listed by practitioners. These opportunities involve a shift from practitioners as users of scientific knowledge and evidence, to practitioners involved in the co-production of evidence needed to increase the effectiveness of restoration interventions.

  16. A Novel Neutral Point Voltage Control Strategy for Three-Level NPC APF Based on SVPWM

    Directory of Open Access Journals (Sweden)

    Yao Xiaolong

    2015-01-01

    Full Text Available The unbalance of the neutral point voltage is an inherent problem of three-level neutral-point-clamped (NPC Active Power Filter (APF; this paper analyzes the causes of unbalanced neutral point voltage and studies the reason of the unbalance of the neutral point voltage. A novel neutral point voltage control strategy using Space Vector Pulse Width Modulation (SVPWM is proposed. The proposed strategy is based on the traditional SVPWM, by controlling the effect time of small vector, which can change the state of the midpoint voltage fluctuation, and the neutral point voltage can be maintained balance. The influence of the vector on neutral point balance is investigated in depth. Simulation results show the neutral point voltage balancing control strategy based on SPWM is effective.

  17. Using a Voltage Domain Programmable Technique for Low-Power Management Cell-Based Design

    Directory of Open Access Journals (Sweden)

    Ching-Hwa Cheng

    2011-09-01

    Full Text Available The Multi-voltage technique is an effective way to reduce power consumption. In the proposed cell-based voltage domain programmable (VDP technique, the high and low voltages applied to logic gates are programmable. The flexible voltage domain reassignment allows the chip performance and power consumption to be dynamically adjusted. In the proposed technique, the power switches possess the feature of flexible programming after chip manufacturing. This VDP method does not use an external voltage regulator to regulate the supply voltage level from outside of the chip but can be easily integrated within the design. This novel technique is proven by use of a video decoder test chip, which shows 55% and 61% power reductions compared to conventional single-Vdd and low-voltage designs, respectively. This power-aware performance adjusting mechanism shows great power reduction with a good power-performance management mechanism.

  18. Enhanced Voltage Control of VSC-HVDC Connected Offshore Wind Farms Based on Model Predictive Control

    DEFF Research Database (Denmark)

    Guo, Yifei; Gao, Houlei; Wu, Qiuwei

    2017-01-01

    This paper proposes an enhanced voltage control strategy (EVCS) based on model predictive control (MPC) for voltage source converter based high voltage direct current (VSCHVDC) connected offshore wind farms (OWFs). In the proposed MPC based EVCS, all wind turbine generators (WTGs) as well...... as the wind farm side VSC are optimally coordinated to keep voltages within the feasible range and reduce system power losses. Considering the high ratio of the OWF collector system, the effects of active power outputs of WTGs on voltage control are also taken into consideration. The predictive model of VSC...... with a typical cascaded control structure is derived in details. The sensitivity coefficients are calculated by an analytical method to improve the computational efficiency. A VSC-HVDC connected OWF with 64 WTGs was used to validate the proposed voltage control strategy....

  19. Short-Term State Forecasting-Based Optimal Voltage Regulation in Distribution Systems: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Rui; Jiang, Huaiguang; Zhang, Yingchen

    2017-05-17

    A novel short-term state forecasting-based optimal power flow (OPF) approach for distribution system voltage regulation is proposed in this paper. An extreme learning machine (ELM) based state forecaster is developed to accurately predict system states (voltage magnitudes and angles) in the near future. Based on the forecast system states, a dynamically weighted three-phase AC OPF problem is formulated to minimize the voltage violations with higher penalization on buses which are forecast to have higher voltage violations in the near future. By solving the proposed OPF problem, the controllable resources in the system are optimally coordinated to alleviate the potential severe voltage violations and improve the overall voltage profile. The proposed approach has been tested in a 12-bus distribution system and simulation results are presented to demonstrate the performance of the proposed approach.

  20. Decentralized control for renewable DC Microgrid with composite energy storage system and UC voltage restoration connected to the grid

    DEFF Research Database (Denmark)

    Bastos, Renan F.; Dragicevic, Tomislav; Guerrero, Josep M.

    2016-01-01

    or load connections. The proposed strategy uses as input for the batteries control only the DC-link voltage and state of charge (SOC), while for the UC only the DC-link voltage and UC terminal voltage are used to achieve the power sharing among the storage devices, equalization of the batteries......In this paper we propose a new decentralized control strategy applied to a DC Microgrid in order to manage the power delivery of storage devices into a common DC-link, avoiding high-bandwidth communication (HBC) between the storage devices (SD) and alternative sources. Batteries and Ultracapacitors...... (UC) are used as SD and the common DC-link is fed by alternative sources such as photovoltaic panels, wind turbines and fuel cells as well. The batteries are used to supply/absorb extra power in steady-state regime while the UC absorbs the power transients caused by variations on the power production...

  1. Tracing current-voltage curve of solar panel Based on LabVIEW Arduino Interfacing

    OpenAIRE

    Rachid, CHENNI

    2015-01-01

    This study describes a low cost system to measure current and power-voltage characteristics of photovoltaic (PV) silicon solar panel under natural conditions based on LabVIEW software. The desired parameters of PV panel including fill factor, max power, short-circuit current, open-circuit voltage are calculated. The characteristics of the solar panel have been drawn quickly using the MOSFET as an electronic load, which is controlled by means of a suitable gate-source voltage. The new developm...

  2. Process-based principles for restoring river ecosystems

    Science.gov (United States)

    Timothy J. Beechie; David A. Sear; Julian D. Olden; George R. Pess; John M. Buffington; Hamish Moir; Philip Roni; Michael M. Pollock

    2010-01-01

    Process-based restoration aims to reestablish normative rates and magnitudes of physical, chemical, and biological processes that sustain river and floodplain ecosystems. Ecosystem conditions at any site are governed by hierarchical regional, watershed, and reach-scale processes controlling hydrologic and sediment regimes; floodplain and aquatic habitat...

  3. Identifying Challenges to Building an Evidence Base for Restoration Practice

    CSIR Research Space (South Africa)

    Ntshotsho, P

    2015-11-01

    Full Text Available . In this paper, we report on a survey conducted to assess practitioners’ perceptions of the evidence generated in restoration practice in South Africa, as well as challenges encountered in building this evidence base. Contrary to a recent assessment...

  4. Voltage controlled Bi-mode resistive switching effects in MnO2 based devices

    Science.gov (United States)

    Hu, P.; Wu, S. X.; Wang, G. L.; Li, H. W.; Li, D.; Li, S. W.

    2018-01-01

    In this paper, the voltage induced bi-mode resistive switching behavior of an MnO2 thin film based device was studied. The device showed prominent bipolar resistive switching behavior with good reproducibility and high endurance. In addition, complementary resistive switching characteristics can be observed by extending the voltage bias during voltage sweep operations. The electrical measurement data and fitting results indicate that the oxygen vacancies act as defects to form a conductive path, which is connective or disrupted to realize a low resistive state or a high resistive state. Changing the sweep voltage can tune the oxygen vacancies distribution, which will achieve complementary resistive switching.

  5. Voltage and frequency control of wind-powered islanded microgrids based on induction generator and STATCOM

    DEFF Research Database (Denmark)

    Bouzid, Allal; Sicard, Pierre; Guerrero, Josep M.

    2015-01-01

    This paper presents a comprehensive modeling of a three-phase cage induction machine used as a self-excited squirrel-cage induction generator (SEIG), and discusses the regulation of the voltage and frequency of a self-excited SEIG based on the action of the static synchronous Compensator (STATCOM......). The STATCOM with the proposed controller consists of a three-phase voltage-sourced inverter and a DC voltage. The compensator can provide the active and reactive powers and regulate AC system bus voltage and the frequency, but also may enhance the load stability. Moreover, a feed forward control method...

  6. Exploration of fluorescent protein voltage probes based on circularly permuted fluorescent proteins

    Directory of Open Access Journals (Sweden)

    Sunita G Gautam

    2009-10-01

    Full Text Available Genetically-encoded fluorescent protein voltage sensors are promising tools for optical monitoring of the electrical activity of cells. Over the last decade, several designs of fusion proteins have been explored and some of them have proven to be sensitive enough to record membrane voltage transients from single mammalian cells. Most prominent are the families of VSFPs (Voltage Sensitive Fluorescent Proteins that utilize the voltage sensor domain of Ci-VSP (Ciona Intestinalis voltage sensor-containing phosphatase. The voltage sensitivity of the fluorescence readout of these previously reported membrane potential indicators is achieved either via a change in the efficiency of fluorescence resonance energy transfer (FRET between two fluorescent protein (FP spectral variants or via modulation in the fluorescence intensity of a single FP. Here, we report our exploration on a third VSFP design principle based on circularly-permuted fluorescent protein (cpFP variants. Using circularly-permuted EGFP derived from GCaMP2 and two newly generated circularly-permuted variants of the far-red emitting protein named mKate, we generated and characterized a series of voltage-sensitive probes wherein the cpFPs were fused to the voltage sensor domain of Ci-VSP. The most promising variants were based on circularly permuted mKate with new N- and C-termini given by residues 180 and 182. Even so their voltage sensitivity was relatively modest, they constitute a proof of principle for this novel protein design.

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

    NARCIS (Netherlands)

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

    2009-01-01

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

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

    DEFF Research Database (Denmark)

    2013-01-01

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

  9. Effect of write voltage and frequency on the reliability aspects of memristor-based RRAM

    Science.gov (United States)

    Dongale, T. D.; Khot, K. V.; Mohite, S. V.; Desai, N. D.; Shinde, S. S.; Patil, V. L.; Vanalkar, S. A.; Moholkar, A. V.; Rajpure, K. Y.; Bhosale, P. N.; Patil, P. S.; Gaikwad, P. K.; Kamat, R. K.

    2017-08-01

    In this paper, we report the effect of the write voltage and frequency on memristor-based resistive random access memory (RRAM). The above-said parameters have been investigated on the linear drift model of the memristor. With a variation of write voltage from 0.2 to 1.2 V and a subsequent frequency modulation from 1, 2, 4, 10, 100 and 200 Hz, the corresponding effects on memory window, low resistance state (LRS) and high resistance state (HRS) have been reported. Thus, the lifetime ( τ) reliability analysis of memristor-based RRAM is carried out using the above results. It is found that the HRS is independent of the write voltage, whereas LRS shows dependency on write voltage and frequency. The simulation results showcase the fact that the memristor possesses higher memory window and lifetime ( τ) in the higher voltage with lower frequency region, which has been attributed to less data losses in the memory architecture.

  10. Storied experiences of school-based habitat restoration

    Science.gov (United States)

    Bell, Anne C.

    The purpose of this study has been to consider the eco-pedagogical promise of school-based habitat restoration. How does the practice of restoration foster a lived sense of being in a more-than-human world1 while inviting alternative approaches to teaching and learning? What opportunities does it offer to resist the societal forces and patterns, reinforced through the school system, which are eroding and effacing human relationships with other life? A literature review sets the broader context for an in-depth exploration of the experiences and understandings of participants (students, teachers, parents) involved in a case study. I proceeded with my research on the assumption that both the discursive and non-discursive dimensions of habitat restoration were key to appreciating its eco-pedagogical potential. Through participant observation over a ten month period, interviewing and a survey, I listened to some of the ways that habitat restoration challenged the typically disembodied, decontextualized organization of schooling by privileging hands-on involvement and encouraging attentive, caring relationships within the human and natural communities of which students were a part. I investigated particular storylines and metaphors which encoded and supported participants' endeavours, especially with regard to their potential to disrupt human-centered values and beliefs. This study suggests that the promise of habitat restoration lies in the openings created to attune to and interact with human and nonhuman others in fully embodied, locally situated and personally meaningful ways. Participants overwhelmingly attested to the importance of the experience of restoration which many deemed to be memorable and motivating and to provide fertile ground for future engagements in/for nature and society. As participants attended to the nuances and complexities of their interactions with a specific place and its inhabitants, their intimate involvement added a depth of feeling and

  11. Carrier-Based Common Mode Voltage Control Techniques in Three-Level Diode-Clamped Inverter

    Directory of Open Access Journals (Sweden)

    Pradyumn Chaturvedi

    2012-01-01

    Full Text Available Switching converters are used in electric drive applications to produce variable voltage, variable frequency supply which generates harmful large dv/dt and high-frequency common mode voltages (CMV. Multilevel inverters generate lower CMV as compared to conventional two-level inverters. This paper presents simple carrier-based technique to control the common mode voltages in multilevel inverters using different structures of sine-triangle comparison method such as phase disposition (PD, phase opposition disposition (POD by adding common mode voltage offset signal to actual reference voltage signal. This paper also presented the method to optimize the magnitude of this offset signal to reduce CMV and total harmonic distortion in inverter output voltage. The presented techniques give comparable performance as obtained in complex space vector-based control strategy, in terms of number of commutations, magnitude, and rate of change of CMV and harmonic profile of inverter output voltage. Simulation and experimental results presented confirm the effectiveness of the proposed techniques to control the common mode voltages.

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

    Directory of Open Access Journals (Sweden)

    Rui Li

    2016-12-01

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

  13. Speed Control of Induction Machine Based on Matrix Converter with Unbalanced Input Voltage

    Directory of Open Access Journals (Sweden)

    Malek Mohammadrezaei

    2011-07-01

    Full Text Available Matrix Converter (MC is a direct energy conversion device with high input power factor. As a device without dc link elements, its output characteristic and reliability can be degraded by ac line side disturbances. This has attracted many researchers to make efforts to solve this problem. In this paper, under unbalanced input voltage conditions, behaviors of the MC controlled with Venturini method are analyzed. The output voltage is estimated and a PI controller compensation method to prevent negative effects of the input voltage harmonics is proposed. Using this technique, output harmonic contents are reduced and stable control of the load voltages and currents is ensured. The MC is used for fed induction motor that reference voltage for converter is computed with controller based on input-output feed-back linearization. Simulation results are presented in the paper to verify effectiveness of the approach.

  14. Switched Reluctance Generator Output Voltage Ripple Reduction Based on Fuzzy Sliding Mode

    Directory of Open Access Journals (Sweden)

    Xia Fei

    2015-01-01

    Full Text Available Aiming at the problem of Switched Reluctance Generator output voltage ripple, this paper designs a fuzzy sliding mode controller based on the analysis of various factors affecting the output voltage ripple. The traditional sliding mode controller has quick convergence, but it has chattering problem. This paper introduces the fuzzy control to select the appropriate sliding mode gain. It can combine with traditional angle control to adjust the output voltage by adjusting the conduction angle. It is more effective in shortening the adjustment time and reducing the overshoot and steady-state of error compared with the classical PID control. Meanwhile, it also solves the chattering problem of traditional sliding mode control. Finally, it makes use of nonlinear model structure to validate that it is effective in restraining voltage ripple and improving the dynamic performance of the system and the voltage quality.

  15. PSO-Based Voltage Control Strategy for Loadability Enhancement in Smart Power Grids

    Directory of Open Access Journals (Sweden)

    Heng-Yi Su

    2016-12-01

    Full Text Available This paper proposes a new voltage control methodology using the particle swarm optimization (PSO technique for smart grid loadability enhancement. The goal of this paper is to achieve reliable and efficient voltage profile/stability regulation in power grids. This methodology is based on the decouple power flow equations and the worst-case design technique. Specifically, the secondary voltage control (SVC problem is formulated as an L-infinity norm minimization problem which considers overall load voltage deviations in electrical power systems as an objective model, and the PSO technique is employed to determine a robust control action which aims to improve voltage profile and to enlarge transmission grid loadability by optimal coordinated control of VAR sources. The methodology was successfully tested on several IEEE benchmark systems.

  16. GaN-Based, Low-Voltage Avalanche Photodiodes for Robust and Compact UV Imagers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase I SBIR program is directed toward the development of a novel low-voltage (~10V) AlGaN-based multi-quantum well (MQW) avalanche photodiode (APD) on...

  17. Nanotechnology-based restorative materials for dental caries management.

    Science.gov (United States)

    Melo, Mary A S; Guedes, Sarah F F; Xu, Hockin H K; Rodrigues, Lidiany K A

    2013-08-01

    Nanotechnology has been applied to dental materials as an innovative concept for the development of materials with better properties and anticaries potential. In this review we discuss the current progress and future applications of functional nanoparticles incorporated in dental restorative materials as useful strategies to dental caries management. We also overview proposed antimicrobial and remineralizing mechanisms. Nanomaterials have great potential to decrease biofilm accumulation, inhibit the demineralization process, to be used for remineralizing tooth structure, and to combat caries-related bacteria. These results are encouraging and open the doors to future clinical studies that will allow the therapeutic value of nanotechnology-based restorative materials to be established. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. High-Speed Fuses in IGBT based Voltage Source Converters

    DEFF Research Database (Denmark)

    Iov, Florin; Blaabjerg, Frede; Rasmussen, Henrik

    2005-01-01

    The demand for protection of power electronic applications has during the last couple of years increased regarding the high-power IGBT modules. Even with an active protection, a high power IGBT still has a risk of exhibiting a violent rupture in the case of a fault if IGBT fuses do not protect it....... By introducing fuses into voltage source converters a better protection of IGBTs can be achieved. This paper is a complete overview of a research project carried out in cooperation by Aalborg University, Denmark and Cooper Bussmann International. This paper discusses three main issues regarding the IGBT fuse...... protection. First, the problem of adding inductance in the DC-link circuit is treated, second a short discussion of the protection of the IGBT module is done, and finally, the impact of the high frequency loading on the current carrying capability of the fuses is presented....

  19. Single Active Element Based Voltage-Mode Multifunction Filter

    Directory of Open Access Journals (Sweden)

    Jitendra Mohan

    2014-01-01

    Full Text Available The paper presents a new voltage-mode multifunction filter. The proposed filter employs single modified fully differential second generation current conveyor (FDCCII, two grounded capacitors, and three resistors. The proposed circuit enjoys the employment of two grounded capacitors (attractive for absorbing shunt parasitic capacitance and ideal for IC implementation. The proposed circuit provides all five generic filter responses (low pass (LP, high pass (HP, band pass (BP, notch (NH, and all pass (AP filter responses simultaneously with single input. The novel proposed filter has low active and passive sensitivities. A number of time domain and frequency domain simulation results depicted through PSPICE using 0.18 µm TSMC process parameters are included to validate the theory. The proposed circuit is expected to enhance the existing knowledge on the subject.

  20. A modelling of AC voltage stabilizer based on a hybrid transformer with matrix converter

    Directory of Open Access Journals (Sweden)

    Szcześniak Paweł

    2017-06-01

    Full Text Available This article presents a study of an AC voltage stabilizer based on a three-phase hybrid transformer combined with a matrix converter. The proposed solution is used to control AC voltage amplitude and phase shift. By adjustment of these voltage parameters we can reduce the effects of overvoltage, voltage dips or lamp flicker. Such negative phenomena are very significant, particularly from the perspective of the final consumer and sensitive loads connected to the power network. Often the voltage in the power system can be adjusted using a mechanical or thyristor controlled regulator, which in a stepwise manner switches the taps of the electromagnetic transformer. The method for obtaining continuous control of the voltage magnitude and phase shift with the use of a conventional transformer with two output windings and a matrix converter is presented in this paper. The operating principles, mathematical model and properties of the proposed voltage stabilizers are discussed in this paper. The main part of the article will be devoted to the mathematical model which is based on an averaged equation. Computer simulation results are presented and compared with the results of a mathematical study.

  1. Optimization of Contact Force and Pull-in Voltage for Series based MEMS Switch

    Directory of Open Access Journals (Sweden)

    Abhijeet KSHIRSAGAR

    2010-04-01

    Full Text Available Cantilever based metal-to-metal contact type MEMS series switch has many applications namely in RF MEMS, Power MEMS etc. A typical MEMS switch consists of a cantilever as actuating element to make the contact between the two metal terminals of the switch. The cantilever is pulled down by applying a pull-in voltage to the control electrode that is located below the middle portion of the cantilever while only the tip portion of the cantilever makes contact between the two terminals. Detailed analysis of bending of the cantilever for different pull-in voltages reveals some interesting facts. At low pull-in voltage the cantilever tip barely touches the two terminals, thus resulting in very less contact area. To increase contact area a very high pull-in voltage is applied, but it lifts the tip from the free end due to concave curving of the cantilever in the middle region of the cantilever where the electrode is located. Again it results in less contact area. Furthermore, the high pull-in voltage produces large stress at the base of the cantilever close to the anchor. Therefore, an optimum, pull-in voltage must exist at which the concave curving is eliminated and contact area is maximum. In this paper authors report the finding of optimum contact force and pull-in voltage.

  2. Genetic Algorithm-Based Artificial Neural Network for Voltage Stability Assessment

    Directory of Open Access Journals (Sweden)

    Garima Singh

    2011-01-01

    Full Text Available With the emerging trend of restructuring in the electric power industry, many transmission lines have been forced to operate at almost their full capacities worldwide. Due to this, more incidents of voltage instability and collapse are being observed throughout the world leading to major system breakdowns. To avoid these undesirable incidents, a fast and accurate estimation of voltage stability margin is required. In this paper, genetic algorithm based back propagation neural network (GABPNN has been proposed for voltage stability margin estimation which is an indication of the power system's proximity to voltage collapse. The proposed approach utilizes a hybrid algorithm that integrates genetic algorithm and the back propagation neural network. The proposed algorithm aims to combine the capacity of GAs in avoiding local minima and at the same time fast execution of the BP algorithm. Input features for GABPNN are selected on the basis of angular distance-based clustering technique. The performance of the proposed GABPNN approach has been compared with the most commonly used gradient based BP neural network by estimating the voltage stability margin at different loading conditions in 6-bus and IEEE 30-bus system. GA based neural network learns faster, at the same time it provides more accurate voltage stability margin estimation as compared to that based on BP algorithm. It is found to be suitable for online applications in energy management systems.

  3. Coordinated Voltage Control Scheme for SEIG-Based Wind Park Utilizing Substation STATCOM and ULTC Transformer

    DEFF Research Database (Denmark)

    S. El Moursi, Mohamed; Bak-Jensen, Birgitte; Abdel-Rahman, Mansour Hassan

    2011-01-01

    and optimal tracking secondary voltage control for wind parks based on self-excited induction generators which comprise STATCOM and under-load tap changer (ULTC) substation transformers. The voltage controllers for the STATCOM and ULTC transformer are coordinated and ensure the voltage support. In steady...... of the short circuit ratio of the interconnection and the inherent communication delay between the wind park and the remote bus on the performance of the controllers and the maximum critical clearing time of fault are considered. Simulation results are presented to demonstrate the performance...

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

    DEFF Research Database (Denmark)

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

    2015-01-01

    The capacitor voltage feedback active damping control is an attractive way to suppress LCL-filter resonance especially for the systems where the capacitor voltage is used for grid synchronization, since no extra sensors are added. The derivative is the core of the capacitor voltage feedback active...... damping control. However, in digital systems, the discrete implementation of the derivative suffers from noise amplification and accuracy issues. To overcome these drawbacks, this paper proposes a new derivative method based on Second-Order Generalized Integrator. Theoretical study shows that the proposed...

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

    DEFF Research Database (Denmark)

    Wang, Yun; Wu, Qiuwei; Gong, Wenming

    2016-01-01

    This paper proposes an H∞ robust current controller for doubly fed induction generator (DFIG) based wind turbines (WTs) subject to grid voltage distortions. The controller is to mitigate the impact of the grid voltage distortions on rotor currents with DFIG parameter perturbation. The grid voltage...... are designed to efficiently track the unbalanced current components and the 5th and 7th background harmonics. The robust stability (RS) and robust performance (RP) of the proposed controller are verified by the structured singular value µ. The performance of the H∞ robust current controller was demonstrated...

  6. A Combined Thermo-Electrostatic MEMS-Based Switch with Low Actuation Voltage

    Directory of Open Access Journals (Sweden)

    Parisa MAHMOUDI

    2010-04-01

    Full Text Available Requirement of voltage up-converters due to high pull-in voltage is one of the main problems by merely electrostatic actuated MEMS-based Switches. Thermally actuated switches are another alternatives but with very high power dissipation. In this paper a low voltage switch is demonstrated, which uses a combined thermo-electrostatic actuator. The switch can be integrated with standard CMOS circuits without any up-converters. Thermally power dissipation for the switch is lower than just thermal actuators. The switching time is about 70 ms and the maximal temperature of thermal actuator is lower than 150 oC which cannot cause any longtime damage.

  7. Comparative Study of Breakdown Voltage of Mineral, Synthetic and Natural Oils and Based Mineral Oil Mixtures under AC and DC Voltages

    OpenAIRE

    Abderrahmane Beroual; Usama Khaled; Phanuel Seraphine Mbolo Noah; Henry Sitorus

    2017-01-01

    This paper deals with a comparative study of AC and DC breakdown voltages of based mineral oil mixtures with natural and synthetic esters mainly used in high voltage power transformers. The goal was to analyze the performances of oil mixtures from the dielectric withstand point of view and to predict the behavior of transformers originally filled with mineral oil and re-filled with synthetic or natural ester oils when emptied for maintenance. The study concerns mixtures based on 20%, 50%, and...

  8. Online Voltage Stability Assessment for Load Areas Based on the Holomorphic Embedding Method

    DEFF Research Database (Denmark)

    Liu, Chengxi; Wang, Bin; Hu, Fengkai

    2018-01-01

    be calculated based on online state estimation on the entire load area and a measurement-based equivalent for the external system. The HEM employs a power series to calculate an accurate Power-Voltage (P-V) curve at each load bus and accordingly evaluates the voltage stability margin considering load variations......This paper proposes an online steady-state voltage stability assessment scheme to evaluate the proximity to voltage collapse at each bus of a load area. Using a non-iterative holomorphic embedding method (HEM) with a proposed physical germ solution, an accurate loading limit at each load bus can...... and then demonstrated on a load area of the Northeast Power Coordinating Council (NPCC) 48-generator, 140-bus power system....

  9. Coordinated Voltage Control of a Wind Farm based on Model Predictive Control

    DEFF Research Database (Denmark)

    Zhao, Haoran; Wu, Qiuwei; Guo, Qinglai

    2016-01-01

    are calculated based on an analytical method to improve the computation efficiency and overcome the convergence problem. Two control modes are designed for both voltage violated and normal operation conditions. A wind farm with 20 wind turbines was used to conduct case studies to verify the proposed coordinated......This paper presents an autonomous wind farm voltage controller based on Model Predictive Control (MPC). The reactive power compensation and voltage regulation devices of the wind farm include Static Var Compensators (SVCs), Static Var Generators (SVGs), Wind Turbine Generators (WTGs) and On......-Load Tap Changing (OLTC) Transformer, and they are coordinated to keep the voltages of all the buses within the feasible range. Moreover, the reactive power distribution is optimized throughout the wind farm in order to maximize the dynamic reactive power reserve. The sensitivity coefficients...

  10. Effect of strain on voltage-controlled magnetism in BiFeO3-based heterostructures

    Science.gov (United States)

    Wang, J. J.; Hu, J. M.; Yang, T. N.; Feng, M.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.

    2014-01-01

    Voltage-modulated magnetism in magnetic/BiFeO3 heterostructures can be driven by a combination of the intrinsic ferroelectric-antiferromagnetic coupling in BiFeO3 and the antiferromagnetic-ferromagnetic exchange interaction across the heterointerface. However, ferroelectric BiFeO3 film is also ferroelastic, thus it is possible to generate voltage-induced strain in BiFeO3 that could be applied onto the magnetic layer across the heterointerface and modulate magnetism through magnetoelastic coupling. Here, we investigated, using phase-field simulations, the role of strain in voltage-controlled magnetism for these BiFeO3-based heterostructures. It is predicted, under certain condition, coexistence of strain and exchange interaction will result in a pure voltage-driven 180° magnetization reversal in BiFeO3-based heterostructures. PMID:24686503

  11. Sensorless Control Technology for PMSG base on the Dead-time Compensation voltage

    Directory of Open Access Journals (Sweden)

    Yang Li-yong

    2015-01-01

    Full Text Available In order to improve the speed sensorless-control system of PMSG in low speed performance, this paper introduces a novel Dead-time compensation control method .Mathematical model is established according to the Dead-zone of the influence of the voltage source type inverter output voltage. At the same time, the given value of current regulator output voltage has been fixed based on the established model. Then the stator voltage after compensationed is applied to the flux estimation, which improves the performance of flux estimation. Finally, the position and speed of the rotor is estimated based on Back-Electromotive Force, which has Simple algorithm and good robustness. In order to verify the correctness of theoretical analysis, the experiment was done according to the new control method. The results proved the correctness and feasibility of this control method.

  12. Effect of strain on voltage-controlled magnetism in BiFeO₃-based heterostructures.

    Science.gov (United States)

    Wang, J J; Hu, J M; Yang, T N; Feng, M; Zhang, J X; Chen, L Q; Nan, C W

    2014-04-01

    Voltage-modulated magnetism in magnetic/BiFeO3 heterostructures can be driven by a combination of the intrinsic ferroelectric-antiferromagnetic coupling in BiFeO3 and the antiferromagnetic-ferromagnetic exchange interaction across the heterointerface. However, ferroelectric BiFeO3 film is also ferroelastic, thus it is possible to generate voltage-induced strain in BiFeO3 that could be applied onto the magnetic layer across the heterointerface and modulate magnetism through magnetoelastic coupling. Here, we investigated, using phase-field simulations, the role of strain in voltage-controlled magnetism for these BiFeO3-based heterostructures. It is predicted, under certain condition, coexistence of strain and exchange interaction will result in a pure voltage-driven 180° magnetization reversal in BiFeO3-based heterostructures.

  13. Hierarchical Control Scheme for Improving Transient Voltage Recovery of a DFIG-Based WPP

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jinho; Muljadi, Eduard; Kang, Yong Cheol

    2015-06-05

    Modern grid codes require that wind power plants (WPPs) inject reactive power according to the voltage dip at a point of interconnection (POI). This requirement helps to support a POI voltage during a fault. However, if a fault is cleared, the POI and wind turbine generator (WTG) voltages are likely to exceed acceptable levels unless the WPP reduces the injected reactive power quickly. This might deteriorate the stability of a grid by allowing the disconnection of WTGs to avoid any damage. This paper proposes a hierarchical control scheme of a doubly-fed induction generator (DFIG)-based WPP. The proposed scheme aims to improve the reactive power injecting capability during the fault and suppress the overvoltage after the fault clearance. To achieve the former, an adaptive reactive power-to-voltage scheme is implemented in each DFIG controller so that a DFIG with a larger reactive power capability will inject more reactive power. To achieve the latter, a washout filter is used to capture a high frequency component contained in the WPP voltage, which is used to remove the accumulated values in the proportional-integral controllers. Test results indicate that the scheme successfully supports the grid voltage during the fault, and recovers WPP voltages without exceeding the limit after the fault clearance.

  14. Polymerization shrinkage of flowable resin-based restorative materials.

    Science.gov (United States)

    Stavridakis, Minos M; Dietschi, Didier; Krejci, Ivo

    2005-01-01

    This study measured the linear polymerization displacement and polymerization forces induced by polymerization shrinkage of a series of flowable resin-based restorative materials. The materials tested were 22 flowable resin-based restorative materials (Admira Flow, Aelite Flow, Aeliteflow LV, Aria, Crystal Essence, Definite Flow, Dyract Flow, Filtek Flow, FloRestore, Flow-it, Flow-Line, Freedom, Glacier, OmegaFlo, PermaFlo, Photo SC, Revolution 2, Star Flow, Synergy Flow, Tetric Flow, Ultraseal XT and Wave). Measurements for linear polymerization displacement and polymerization forces were performed using custom made measuring devices. Polymerization of the test materials was carried out for 60 seconds by means of a light curing unit, and each property was measured for 180 seconds from the start of curing in eight specimens for each material. Statistical evaluation of the data was performed with one-way analysis of variance (ANOVA), Tukey's Studentized Range (HSD) test (p=0.05) and simple linear regression. A wide range of values was recorded for linear polymerization displacement (26.61 to 80.74 microns) and polymerization forces (3.23 to 7.48 kilograms). Statistically significant differences among materials were found for both properties studied. Very few materials (Freedom, Glacier, and Photo SC) presented low values of linear polymerization displacement and polymerization forces (similar to hybrid resin composites), while the majority of materials presented very high values in both properties studied. Study of the shrinkage kinetics revealed the exponential growth process of both properties. The polymerization forces development exhibited a few seconds delay over linear polymerization displacement. Simple linear regression showed that the two polymerization shrinkage properties that were studied were not highly correlated (r2=0.59).

  15. Low voltage ride-Through strategy based on virtual synchronous generator control

    Science.gov (United States)

    Guo, L.; Su, J. H.; Yu, L.; Lai, J. D.

    2017-06-01

    Inverters controlled in virtual synchronous generator(VSG) method is able to operate in both grid-connected mode and islanding mode. Due to this characteristic, this paper put forwards a low voltage ride-through(LVRT) strategy which is based on VSG control. If the grid voltage sags, VSG can limit the output current amplitude and meanwhile inject reactive power to the grid. Once the voltage drop time exceeds the maximum ride-through time, VSG would smoothly switch to islanding mode and continues to carry loads independently. The proposed strategy achieves a control algorithm unity between normal operating and grid voltage sag status in grid-connected mode. Simulations can support the validity of the strategy.

  16. Comparative Study of Breakdown Voltage of Mineral, Synthetic and Natural Oils and Based Mineral Oil Mixtures under AC and DC Voltages

    Directory of Open Access Journals (Sweden)

    Abderrahmane Beroual

    2017-04-01

    Full Text Available This paper deals with a comparative study of AC and DC breakdown voltages of based mineral oil mixtures with natural and synthetic esters mainly used in high voltage power transformers. The goal was to analyze the performances of oil mixtures from the dielectric withstand point of view and to predict the behavior of transformers originally filled with mineral oil and re-filled with synthetic or natural ester oils when emptied for maintenance. The study concerns mixtures based on 20%, 50%, and 80% of natural and synthetic ester oils. AC breakdown voltages were measured using a sphere-sphere electrode system according to IEC 60156 specifications; the same specification was adopted for DC measurements since there is no standard specifications for this voltage waveform. A statistical analysis of the mean values, standard deviations, and histograms of breakdown voltage data was carried out. The Normal and Weibull distribution functions were used to analyze the experimental data and the best function that the data followed was used to estimate the breakdown voltage with risk of 1%, 10%, and 50% probability. It was shown that whatever the applied voltage waveforms, ester oils always have a significantly higher breakdown voltage than mineral oil. The addition of only 20% of natural or synthetic ester oil was sufficient to considerably increase the breakdown voltage of mineral oil. The dielectric strength of such a mixture is much higher than that of mineral oil alone and can reach that of ester oils. From the point of view of dielectric strength, the mixtures constitute an option for improving the performance of mineral oil. Thus, re-filling of transformers containing up to 20% mineral oil residues with ester oils, does not present any problem; it is even advantageous when considering only the breakdown voltage. Under AC, the mixtures with natural ester always follow the behavior of vegetable oil alone. With the exception of the 20% mixture of natural

  17. Design of a Three-Phase Statcom-Based Inductive Static VAR Compensator Using DC Capacitor Voltage Control Scheme

    OpenAIRE

    Abdulkareem Mokif Obais; Jagadeesh Pasupuleti

    2013-01-01

    In this study, a three-phase continuously controlled harmonic-free inductive static VAR compensator is presented. The compensator is built of a three-phase voltage source inverter based statcom. The phase currents of this compensator are linearly and continuously controlled by the statcom DC capacitor voltage. The control strategy is outlined by a process of forcing the capacitor voltage to follow a certain reference voltage which can be varied linearly from its maximum to its minimum values ...

  18. A physics-based model of threshold voltage for amorphous oxide semiconductor thin-film transistors

    Science.gov (United States)

    Chen, Chi-Le; Chen, Wei-Feng; Zhou, Lei; Wu, Wei-Jing; Xu, Miao; Wang, Lei; Peng, Jun-Biao

    2016-03-01

    In the application of the Lambert W function, the surface potential for amorphous oxide semiconductor thin-film transistors (AOS TFTs) under the subthreshold region is approximated by an asymptotic equation only considering the tail states. While the surface potential under the above-threshold region is approximated by another asymptotic equation only considering the free carriers. The intersection point between these two asymptotic equations represents the transition from the weak accumulation to the strong accumulation. Therefore, the gate voltage corresponding to the intersection point is defined as threshold voltage of AOS TFTs. As a result, an analytical expression for the threshold voltage is derived from this novel definition. It is shown that the threshold voltage achieved by the proposed physics-based model is agreeable with that extracted by the conventional linear extrapolation method. Furthermore, we find that the free charge per unit area in the channel starts increasing sharply from the threshold voltage point, where the concentration of the free carriers is a little larger than that of the localized carriers. The proposed model for the threshold voltage of AOS TFTs is not only physically meaningful but also mathematically convenient, so it is expected to be useful for characterizing and modeling AOS TFTs.

  19. A physics-based model of threshold voltage for amorphous oxide semiconductor thin-film transistors

    Directory of Open Access Journals (Sweden)

    Chi-Le Chen

    2016-03-01

    Full Text Available In the application of the Lambert W function, the surface potential for amorphous oxide semiconductor thin-film transistors (AOS TFTs under the subthreshold region is approximated by an asymptotic equation only considering the tail states. While the surface potential under the above-threshold region is approximated by another asymptotic equation only considering the free carriers. The intersection point between these two asymptotic equations represents the transition from the weak accumulation to the strong accumulation. Therefore, the gate voltage corresponding to the intersection point is defined as threshold voltage of AOS TFTs. As a result, an analytical expression for the threshold voltage is derived from this novel definition. It is shown that the threshold voltage achieved by the proposed physics-based model is agreeable with that extracted by the conventional linear extrapolation method. Furthermore, we find that the free charge per unit area in the channel starts increasing sharply from the threshold voltage point, where the concentration of the free carriers is a little larger than that of the localized carriers. The proposed model for the threshold voltage of AOS TFTs is not only physically meaningful but also mathematically convenient, so it is expected to be useful for characterizing and modeling AOS TFTs.

  20. An inventory of continental U.S. terrestrial candidate ecological restoration areas based on landscape context

    Science.gov (United States)

    James Wickham; Kurt Riitters; Peter Vogt; Jennifer Costanza; Anne Neale

    2017-01-01

    Landscape context is an important factor in restoration ecology, but the use of landscape context for site prioritization has not been as fully developed.We used morphological image processing to identify candidate ecological restoration areas based on their proximity to existing natural vegetation. We identified 1,102,720 candidate ecological restoration areas across...

  1. Repair or replacement of defective restorations by dentists in The Dental Practice-Based Research Network

    DEFF Research Database (Denmark)

    Gordan, Valeria V; Riley, Joseph L; Geraldeli, Saulo

    2012-01-01

    The authors aimed to determine whether dentists in practices belonging to The Dental Practice-Based Research Network (DPBRN) were more likely to repair or to replace a restoration that they diagnosed as defective; to quantify dentists' specific reasons for repairing or replacing restorations......; and to test the hypothesis that certain dentist-, patient- and restoration-related variables are associated with the decision between repairing and replacing restorations....

  2. Adaptive Voltage Stability Protection Based on Load Identification Using Phasor Measurement Units

    DEFF Research Database (Denmark)

    Liu, Leo; Bak, Claus Leth; Chen, Zhe

    2011-01-01

    with respect to load characteristics was evaluated. Based on different load characteristics, different control and protection schemes were implemented, i.e. shunt capacitor connection, on-load tap changer blocking and load shedding. The results showed that load-based adaptive voltage control and protection...

  3. An audit of the quality of base metal cast restorations provided within the restorative department of a UK dental institute.

    Science.gov (United States)

    Beddis, H P; Ridsdale, L; Chin, J S; Nixon, P J

    2014-09-01

    Gold alloy has long been used in dentistry for the fabrication of cast restorations due to its material and clinical properties and known excellent longevity over long-term follow-up. The cost of gold has increased dramatically in recent years (by 450% in the past ten years). The use of base metal alloys as an alternative would lead to a considerable cost saving: a cobalt chromium alloy is around 98% cheaper than gold alloy at the time of writing. NHS regulations state which alloys are permissible for use in cast restorations in dentistry, and certain 'non-precious gold' alloys should not be used. A prospective audit was carried out in our unit into the standard of cast restorations in cobalt-chromium alloy. The standard set before the audit was established by a prior audit of gold alloy restorations with measures of clinical and technical factors. Base-metal alloy restorations were considerably cheaper; but were of a poorer clinical standard than gold-alloy and required more frequent adjustment and remake (17% compared to 5%).

  4. Design of high voltage DC power supply based on LCC resonant converter

    Science.gov (United States)

    Wang, Z. Q.; Liu, Z. G.; Wang, J. J.; Li, G. F.

    2013-03-01

    The aim of this paper is to design a small size, light weight high frequency high voltage (HFHV) power supply. It presents a comprehensive procedure for designing a high output voltage power supply based on series-parallel (LCC) resonant converter, aiming to realize the soft-switching. Through mathematical calculation based on an extensive of the first harmonic analysis, the paper derives the approach of determining the resonant parameters of the LCC converter. Then, a 35 kV power supply featuring a series-parallel resonant converter topology to compensate the distributed parameter is built to verify the correctness of the theory.

  5. FPGA Based Compensation Method for Correcting Distortion in Voltage Inverters

    Science.gov (United States)

    2007-12-01

    Using XILINX® developments tools the SIMULINK® model is converted into VHDL programming code. This code is imbedded into the Virtex IITM FPGA which...based approach but the increased overhead on the DSP would not allow it. 4 D. THESIS ORGANIZATION This thesis is organized as follows Chapter

  6. Opposition-Based Improved PSO for Optimal Reactive Power Dispatch and Voltage Control

    Directory of Open Access Journals (Sweden)

    Shengrang Cao

    2015-01-01

    Full Text Available An opposition-based improved particle swarm optimization algorithm (OIPSO is presented for solving multiobjective reactive power optimization problem. OIPSO uses the opposition learning to improve search efficiency, adopts inertia weight factors to balance global and local exploration, and takes crossover and mutation and neighborhood model strategy to enhance population diversity. Then, a new multiobjective model is built, which includes system network loss, voltage dissatisfaction, and switching operation. Based on the market cost prices, objective functions are converted to least-cost model. In modeling process, switching operation cost is described according to the life cycle cost of transformer, and voltage dissatisfaction penalty is developed considering different voltage quality requirements of customers. The experiment is done on the new mathematical model. Through the simulation of IEEE 30-, 118-bus power systems, the results prove that OIPSO is more efficient to solve reactive power optimization problems and the model is more accurate to reflect the real power system operation.

  7. Shunt PWM advanced var compensators based on voltage source inverters for Facts applications

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, Pedro G.; Misaka, Isamu; Watanabe, Edson H. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia

    1994-12-31

    Increased attention has been given to improving power system operation. This paper presents modeling, analysis and design of reactive shunt power compensators based on PWM-Voltage Source Inverters (Pulse Width Modulation -Voltage Source Inverters). (Pulse Width Modulation - Voltage Source Inverters). The control algorithm is based on new concepts of instantaneous active and reactive power theory. The objective is to show that with a small capacitor in the side of a 3-phase PWM-VSI it is possible to synthesize a variable reactive (capacitive or inductive) device. Design procedures and experimental results are presented. The feasibility of this method was verified by digital simulations and measurements on a small scale model. (author) 9 refs., 12 figs.

  8. Full gate voltage range Lambert-function based methodology for FDSOI MOSFET parameter extraction

    Science.gov (United States)

    Karatsori, T. A.; Theodorou, C. G.; Ioannidis, E. G.; Haendler, S.; Josse, E.; Dimitriadis, C. A.; Ghibaudo, G.

    2015-09-01

    A new full gate voltage range methodology using a Lambert W function based inversion charge model, for extracting the electrical parameters in FDSOI nano-MOSFET devices, has been developed. Split capacitance-voltage measurements carried out on 14 nm technology FDSOI devices show that the inversion charge variation with gate voltage can be well described by a Lambert W function. Based on the drain current equation in the linear region including the inversion charge described by the Lambert function of gate voltage and the standard mobility equation enables five electrical MOSFET parameters to be extracted from experimental Id-Vg measurements (ideality factor, threshold voltage, low field mobility, first and second order mobility attenuation factors). The extracted parameters were compared with those extracted by the well-known Y-function in strong inversion region. The present methodology for extracting the electrical MOSFET parameters was verified over a wide range of channel lengths on nano-scale FDSOI devices, demonstrating its simplicity, accuracy and robustness.

  9. Restoration outcomes after restoring vital teeth with advanced caries lesions: a practice-based retrospective study.

    Science.gov (United States)

    Schwendicke, Falk; Krüger, Hannes; Schlattmann, Peter; Paris, Sebastian

    2016-09-01

    Maintaining pulpal vitality and achieving long-term restoration success are challenging when treating advanced caries lesions. We aimed at assessing success, survival, and influencing factors of treating advanced lesions in general dental practice. Patient record databases from six practices in Germany were assessed. Permanent posterior teeth with lesions radiographically extending into inner dentin with sensible (vital) pulps were retrospectively evaluated. Outcome parameters were success (absence of re-treatment) and survival (absence of extraction). Mean success/survival times were estimated, and effect of treatment modifiers assessed using Lee, Wei, and Amato (LWA) regression. Two hundred thirty-two patients (308 teeth) were assessed. Lesions (93 %) included proximal surfaces. Eight teeth showed preoperative intermitting or provocation pain. Thirty four % of teeth experienced pulpal exposure during excavation. Mean follow-up time was 74 months. Mean success time was 130 months. Teeth (142/308) required re-interventions, mostly due to secondary caries and restorative or endodontic complications. Only 13 teeth required extraction (mean survival time 307 months). Hazard of failure was significantly reduced in younger patients (<40 years) (hazard ratio (HR) [95 % confidence interval (CI)] 0.57 [0.35/0.91]) and teeth without preoperative pain (0.39 [0.17/0.90]). Compared with teeth receiving amalgams, those restored using cements (2.44 [1.05/3.98]) or composites (1.64 [1.15/2.38]) had higher risk of failure. Hazard of extraction was higher in teeth with pulpal exposure (4.90 [1.36/17.7] or cement restorations (23.6 [5.56/100]). Teeth with advanced lesions had high risk of failure, while risk of extraction was low. Teeth treated for advanced lesions required re-treatment frequently but were retained long term. Age, pulpal exposure, and restoration type were associated with risk of failure or extraction.

  10. GPU-based parallel algorithm for blind image restoration using midfrequency-based methods

    Science.gov (United States)

    Xie, Lang; Luo, Yi-han; Bao, Qi-liang

    2013-08-01

    GPU-based general-purpose computing is a new branch of modern parallel computing, so the study of parallel algorithms specially designed for GPU hardware architecture is of great significance. In order to solve the problem of high computational complexity and poor real-time performance in blind image restoration, the midfrequency-based algorithm for blind image restoration was analyzed and improved in this paper. Furthermore, a midfrequency-based filtering method is also used to restore the image hardly with any recursion or iteration. Combining the algorithm with data intensiveness, data parallel computing and GPU execution model of single instruction and multiple threads, a new parallel midfrequency-based algorithm for blind image restoration is proposed in this paper, which is suitable for stream computing of GPU. In this algorithm, the GPU is utilized to accelerate the estimation of class-G point spread functions and midfrequency-based filtering. Aiming at better management of the GPU threads, the threads in a grid are scheduled according to the decomposition of the filtering data in frequency domain after the optimization of data access and the communication between the host and the device. The kernel parallelism structure is determined by the decomposition of the filtering data to ensure the transmission rate to get around the memory bandwidth limitation. The results show that, with the new algorithm, the operational speed is significantly increased and the real-time performance of image restoration is effectively improved, especially for high-resolution images.

  11. GECM-Based Voltage Stability Assessment Using Wide-Area Synchrophasors

    Directory of Open Access Journals (Sweden)

    Heng-Yi Su

    2017-10-01

    Full Text Available Voltage instability is a crucial issue in the secure operation of power grids. Several methods for voltage stability assessment were presented. Some of them are highly computationally intensive, while others are reported not to work properly under all circumstances. This paper proposes a new methodology based on the generator equivalent circuit model (GECM and the phasor measurement unit (PMU technology for online voltage stability monitoring of a power grid. First, the proposed methodology utilizes synchronized phasor (synchrophasor measurements to determine the impedance parameters of a transmission grid by means of the recursive least squares (RLS algorithm. Furthermore, it incorporates the dynamic models of generators to handle the cases with generator reactive power limit violations. After that, an enhanced voltage stability index with GECMs incorporated is developed for reliable and accurate voltage stability assessment. The proposed methodology was first demonstrated on several standard IEEE power systems, and then applied to a practical power system, the Taiwan power (Taipower system. The test results demonstrate the flexibility and effectiveness of the proposed methodology.

  12. Adaptive Hierarchical Voltage Control of a DFIG-Based Wind Power Plant for a Grid Fault

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jinho; Muljadi, Eduard; Park, Jung-Wook; Kang, Yong Cheol

    2016-11-01

    This paper proposes an adaptive hierarchical voltage control scheme of a doubly-fed induction generator (DFIG)-based wind power plant (WPP) that can secure more reserve of reactive power (Q) in the WPP against a grid fault. To achieve this, each DFIG controller employs an adaptive reactive power to voltage (Q-V) characteristic. The proposed adaptive Q-V characteristic is temporally modified depending on the available Q capability of a DFIG; it is dependent on the distance from a DFIG to the point of common coupling (PCC). The proposed characteristic secures more Q reserve in the WPP than the fixed one. Furthermore, it allows DFIGs to promptly inject up to the Q limit, thereby improving the PCC voltage support. To avert an overvoltage after the fault clearance, washout filters are implemented in the WPP and DFIG controllers; they can prevent a surplus Q injection after the fault clearance by eliminating the accumulated values in the proportional-integral controllers of both controllers during the fault. Test results demonstrate that the scheme can improve the voltage support capability during the fault and suppress transient overvoltage after the fault clearance under scenarios of various system and fault conditions; therefore, it helps ensure grid resilience by supporting the voltage stability.

  13. Low voltage driven dielectric electro active polymer actuator with integrated piezoelectric transformer based driver

    DEFF Research Database (Denmark)

    Andersen, Thomas; Rødgaard, Martin Schøler; Thomsen, Ole Cornelius

    2011-01-01

    impulse response and sinusoidal shapes up to 2.5 kV are demonstrated. The control system, together with a carefully designed HV output stage, contributes to low power consumption at a static DEAP force. The HV stage consists of a HV measurement circuit and a triple diode voltage doubler optimized for low...... actuators, a low voltage solution is developed by integrating the driver electronic into a 110 mm tall cylindrical coreless Push InLastor actuator. To decrease the size of the driver, a piezoelectric transformer (PT) based solution is utilized. The PT is essentially an improved Rosen type PT...

  14. Research on Centralized Voltage and Effective Inequality Identification Based on Circuit Analysis Method

    Science.gov (United States)

    Su, Yi; Wang, Feifeng; Lu, Yufeng; Huang, Huimin; Xia, Xiaofei

    2017-09-01

    This paper is based on affine function equation of the grid and OPF problem, discusses the equivalent of some inequality constraints variables optimizing. Further, we propose the model of injection current and set up the constraint sensitivity index of affine characteristics. The index can be used to identify the central point voltage and effective inequality of the system automatically. And then we can know how to compensate reactive power of the corresponding generator node and control the voltage to ensure the quality of the system voltage. When checking the effective inequalities we introduce cross-solving method of power flow. This provide a different idea for solving the power flow. The paper uses the results of the IEEE5 node examples to illustrate the validity and practicality of the proposed method.

  15. Cross-sectional radiographic survey of amalgam and resin-based composite posterior restorations.

    Science.gov (United States)

    Levin, Liran; Coval, Marius; Geiger, Selly B

    2007-06-01

    To compare the failure rate of posterior interproximal amalgam restorations to resin-based composite restorations in a random young adult population. Bilateral bitewing radiographs of 459 young adults were screened. A total of 14,140 interproximal surfaces were examined, recorded, and statistically analyzed. Rate of failure was determined by the number of restorations with radiographic evidence of secondary caries and/or overhanging margins. Of the 650 restored interproximal surfaces (5% of all clearly demarcated interproximal surfaces), 86 (13%) demonstrated distinct interproximal secondary caries and 22 (3%) had overhanging margins. Of the 557 amalgam and 93 resin-based composite interproximal restorations, secondary caries were shown in 46 (8%) and 40 (43%), respectively, and overhanging margins in 21 (4%) and only 1 (1%), respectively. Generally, when secondary caries and overhanging margins were considered, the failure rate of amalgam and resin-based composite interproximal restorations was 12% and 44%, respectively. Higher failure rates were observed in resin-based composite restorations than in amalgam restorations. Secondary caries was the main reason for failure. Overhanging margins were not a primary factor in restoration failure. The vast use of posterior interproximal resin-based composite restorations should be reconsidered, and their limited long-term performance should be kept in mind.

  16. Impact-Based Electromagnetic Energy Harvester with High Output Voltage under Low-Level Excitations

    Directory of Open Access Journals (Sweden)

    Qian Luo

    2017-11-01

    Full Text Available To expand the applications of vibrational energy harvesters (VEHs as power sources of wireless sensor nodes, it is of significance to improve the scavenging efficiency for the broadband, low-frequency, and low-level vibrational energy. The output voltages of electromagnetic vibrational energy harvesters (EMVEHs are usually low, which complicates the power management circuit by an indispensable voltage boosting element. To this end, an impact-based non-resonant EMVEH mainly composed of an outer frame and an inner frame on rollers is proposed. Numerical simulations based on a mathematical model of the harvester are conducted to analyze the effects of structural parameters on the output performance. Under base excitation of 0.1 and 0.3 (where g is the gravitational acceleration, 1 g = 9.8 m · s − 2 , the experimental maximum root mean square voltages of a harvester prototype across a resistor of 11 kΩ are as high as 7.6 and 16.5 V at 6.0 and 8.5 Hz, respectively, with the maximum output powers of 5.3 and 24.8 mW, or the power densities of 54.6 and 256 μW cm−3. By using a management circuit without a voltage boosting element, a wireless sensor node driven by the prototype can measure and transmit the temperature and humidity every 20 s under base excitation of 0.1 g at 5.4 Hz.

  17. A Voltage Feedback Based Harmonic Compensation Strategy for Current-Controlled Converters

    DEFF Research Database (Denmark)

    Zhao, Xin; Meng, Lexuan; Xie, Chuan

    2017-01-01

    advantages of the proposed method include: 1) it realizes seamless interface of HC with inner fundamental current control loop; 2) compared with conventional active power filtering method, it does not require remote load harmonic current measurement since it is local voltage detection based; 3) compared...

  18. Improved Control Strategy for DFIG-based Wind Energy Conversion System during Grid Voltage Disturbances

    DEFF Research Database (Denmark)

    Zhu, Rongwu

    For the DFIG-based WECS, due to the direct connection between the stator and grid, the DFIG is sensitive to grid voltage disturbances. The effects from the power grid may produce the oscillations of the stator active and reactive power, oscillatory electromagnetic torque, and distorted stator and...

  19. A Low-Voltage Mobility-Based Frequency Reference for Crystal-Less ULP Radios

    NARCIS (Netherlands)

    Sebastiano, Fabio; Breems, Lucien J.; Makinwa, Kofi A.A.; Dargo, Salvatore; Drago, S.; Leenaerts, Domine M.W.; Nauta, Bram

    2009-01-01

    The design of a 100 kHz frequency reference based on the electron mobility in a MOS transistor is presented. The proposed low-voltage low-power circuit requires no off-chip components, making it suitable for application in wireless sensor networks (WSN). After a single-point calibration, the spread

  20. A Low-Voltage Mobility-Based Frequency Reference for Crystal-Less ULP Radios

    NARCIS (Netherlands)

    Sebastiano, Fabio; Breems, Lucien; Makinwa, Kofi; Drago, S.; Leenaerts, Domine; Nauta, Bram

    2008-01-01

    The design of a 100 kHz frequency reference based on the electron mobility in a MOS transistor is presented. The proposed low-voltage low-power circuit requires no off-chip components, making it suitable for Wireless Sensor Networks (WSN) applications. After one-point calibration the spread of its

  1. A practice-based research network on the survival of ceramic inlay/onlay restorations

    NARCIS (Netherlands)

    Collares, K.; Correa, M.B.; Laske, M.; Kramer, E.; Reiss, B.; Moraes, R.R.; Huysmans, M.C.; Opdam, N.J.

    2016-01-01

    OBJECTIVE: To evaluate prospectively the longevity of ceramic inlay/onlay restorations placed in a web-based practice-based research network and to investigate risk factors associated with restoration failures. MATERIALS AND METHODS: Data were collected by a practice-based research network called

  2. Voltage adjusting characteristics in terahertz transmission through Fabry-Pérot-based metamaterials

    Directory of Open Access Journals (Sweden)

    Jun Luo

    2015-10-01

    Full Text Available Metallic electric split-ring resonators (SRRs with featured size in micrometer scale, which are connected by thin metal wires, are patterned to form a periodically distributed planar array. The arrayed metallic SRRs are fabricated on an n-doped gallium arsenide (n-GaAs layer grown directly over a semi-insulating gallium arsenide (SI-GaAs wafer. The patterned metal microstructures and n-GaAs layer construct a Schottky diode, which can support an external voltage applied to modify the device properties. The developed architectures present typical functional metamaterial characters, and thus is proposed to reveal voltage adjusting characteristics in the transmission of terahertz waves at normal incidence. We also demonstrate the terahertz transmission characteristics of the voltage controlled Fabry-Pérot-based metamaterial device, which is composed of arrayed metallic SRRs. To date, many metamaterials developed in earlier works have been used to regulate the transmission amplitude or phase at specific frequencies in terahertz wavelength range, which are mainly dominated by the inductance-capacitance (LC resonance mechanism. However, in our work, the external voltage controlled metamaterial device is developed, and the extraordinary transmission regulation characteristics based on both the Fabry-Pérot (FP resonance and relatively weak surface plasmon polariton (SPP resonance in 0.025-1.5 THz range, are presented. Our research therefore shows a potential application of the dual-mode-resonance-based metamaterial for improving terahertz transmission regulation.

  3. Beam Based RF Voltage Measurements and Longitudinal Beam Tomography at the Fermilab Booster

    Energy Technology Data Exchange (ETDEWEB)

    Bhat, C. M. [Fermilab; Bhat, S. [Fermilab

    2017-10-19

    Increasing proton beam power on neutrino production targets is one of the major goals of the Fermilab long term accelerator programs. In this effort, the Fermilab 8 GeV Booster synchrotron plays a critical role for at least the next two decades. Therefore, understanding the Booster in great detail is important as we continue to improve its performance. For example, it is important to know accurately the available RF power in the Booster by carrying out beam-based measurements in order to specify the needed upgrades to the Booster RF system. Since the Booster magnetic field is changing continuously measuring/calibrating the RF voltage is not a trivial task. Here, we present a beam based method for the RF voltage measurements. Data analysis is carried out using computer programs developed in Python and MATLAB. The method presented here is applicable to any RCS which do not have flat-bottom and flat-top in the acceleration magnetic ramps. We have also carried out longitudinal beam tomography at injection and extraction energies with the data used for RF voltage measurements. Beam based RF voltage measurements and beam tomography were never done before for the Fermilab Booster. The results from these investigations will be very useful in future intensity upgrades.

  4. Rimonabant improves metabolic parameters partially attributed to restoration of high voltage-activated Ca2+ channels in skeletal muscle in HFD-fed mice

    Directory of Open Access Journals (Sweden)

    B. Chen

    Full Text Available Cannabinoid type 1 receptor (CB1R inhibition tends to be one of the promising strategies for the treatment of obesity and other related metabolic disorders. Although CB1R inhibition may cause adverse psychiatric effects including depression and anxiety, the investigation of the role of peripheral CB1R on weight loss and related metabolic parameters are urgently needed. We first explored the effect of rimonabant, a selective CB1R antagonist/inverse agonist, on some metabolic parameters in high fat-diet (HFD-induced obesity in mice. Then, real-time PCR and electrophysiology were used to explore the contribution of high voltage-activated Ca2+ channels (HVACCs, especially Cav1.1, on rimonabant's effect in skeletal muscle (SM in HFD-induced obesity. Five-week HFD feeding caused body weight gain, and decreased glucose/insulin tolerance in mice compared to those in the regular diet group (P<0.05, which was restored by rimonabant treatment compared to the HFD group (P<0.05. Interestingly, HVACCs and Cav1.1 were decreased in soleus muscle cells in the HFD group compared to the control group. Daily treatment with rimonabant for 5 weeks was shown to counter such decrease (P<0.05. Collectively, our findings provided a novel understanding for peripheral CB1R's role in the modulation of body weight and glucose homeostasis and highlight peripheral CB1R as well as Cav1.1 in the SM as potential targets for obesity treatment.

  5. Distributed Reactive Power Control based Conservation Voltage Reduction in Active Distribution Systems

    Directory of Open Access Journals (Sweden)

    EMIROGLU, S.

    2017-11-01

    Full Text Available This paper proposes a distributed reactive power control based approach to deploy Volt/VAr optimization (VVO / Conservation Voltage Reduction (CVR algorithm in a distribution network with distributed generations (DG units and distribution static synchronous compensators (D-STATCOM. A three-phase VVO/CVR problem is formulated and the reactive power references of D-STATCOMs and DGs are determined in a distributed way by decomposing the VVO/CVR problem into voltage and reactive power control. The main purpose is to determine the coordination between voltage regulator (VR and reactive power sources (Capacitors, D-STATCOMs and DGs based on VVO/CVR. The study shows that the reactive power injection capability of DG units may play an important role in VVO/CVR. In addition, it is shown that the coordination of VR and reactive power sources does not only save more energy and power but also reduces the power losses. Moreover, the proposed VVO/CVR algorithm reduces the computational burden and finds fast solutions. To illustrate the effectiveness of the proposed method, the VVO/CVR is performed on the IEEE 13-node test system feeder considering unbalanced loading and line configurations. The tests are performed taking the practical voltage-dependent load modeling and different customer types into consideration to improve accuracy.

  6. Characterizing fish responses to a river restoration over 21 years based on species' traits.

    Science.gov (United States)

    Höckendorff, Stefanie; Tonkin, Jonathan D; Haase, Peter; Bunzel-Drüke, Margret; Zimball, Olaf; Scharf, Matthias; Stoll, Stefan

    2017-10-01

    Understanding restoration effectiveness is often impaired by a lack of high-quality, long-term monitoring data and, to date, few researchers have used species' trait information to gain insight into the processes that drive the reaction of fish communities to restoration. We examined fish-community responses with a highly resolved data set from 21 consecutive years of electrofishing (4 years prerestoration and 17 years postrestoration) at multiple restored and unrestored reaches from a river restoration project on the Lippe River, Germany. Fish abundance peaked in the third year after the restoration; abundance was 6 times higher than before the restoration. After 5-7 years, species richness and abundance stabilized at 2 and 3.5 times higher levels relative to the prerestoration level, respectively. However, interannual variability of species richness and abundance remained considerable, illustrating the challenge of reliably assessing restoration outcomes based on data from individual samplings, especially in the first years following restoration. Life-history and reproduction-related traits best explained differences in species' responses to restoration. Opportunistic short-lived species with early female maturity and multiple spawning runs per year exhibited the strongest increase in abundance, which reflected their ability to rapidly colonize new habitats. These often small-bodied and fusiform fishes typically live in dynamic and ephemeral instream and floodplain areas that river-habitat restorations often aim to create, and in this case their increases in abundance indicated successful restoration. Our results suggest that a greater consideration of species' traits may enhance the causal understanding of community processes and the coupling of restoration to functional ecology. Trait-based assessments of restoration outcomes would furthermore allow for easier transfer of knowledge across biogeographic borders than studies based on taxonomy. © 2017 Society for

  7. Optimal power and performance trade-offs for dynamic voltage scaling in power management based wireless sensor node

    Directory of Open Access Journals (Sweden)

    Anuradha Pughat

    2016-09-01

    Full Text Available Dynamic voltage scaling contributes to a significant amount of power saving, especially in the energy constrained wireless sensor networks (WSNs. Existing dynamic voltage scaling techniques make the system slower and ignore the event miss rate. This results in degradation of the system performance when there is non-stationary workload at input. The overhead due to transition between voltage level and discrete voltage levels are also the limitations of available dynamic voltage scaling (DVS techniques at sensor node (SN. This paper proposes a workload dependent DVS based MSP430 controller model used for SN. An online gradient estimation technique has been used to optimize power and performance trade-offs. The analytical results are validated with the simulation results obtained using simulation tool “SimEvents” and compared with the available AT9OS8535 controller. Based on the stochastic workload, the controller's input voltage, operational frequency, utilization, and average wait time of events are obtained.

  8. A Function-Based Framework for Stream Assessment & Restoration Projects

    Science.gov (United States)

    This report lays out a framework for approaching stream assessment and restoration projects that focuses on understanding the suite of stream functions at a site in the context of what is happening in the watershed.

  9. A 24-month evaluation of amalgam and resin-based composite restorations

    DEFF Research Database (Denmark)

    McCracken, Michael S; Gordan, Valeria V; Litaker, Mark S

    2013-01-01

    Knowing which factors influence restoration longevity can help clinicians make sound treatment decisions. The authors analyzed data from The National Dental Practice-Based Research Network to identify predictors of early failures of amalgam and resin-based composite (RBC) restorations....

  10. 18-year survival of posterior composite resin restorations with and without glass ionomer cement as base.

    Science.gov (United States)

    van de Sande, Françoise H; Rodolpho, Paulo A Da Rosa; Basso, Gabriela R; Patias, Rômulo; da Rosa, Quéren F; Demarco, Flávio F; Opdam, Niek J; Cenci, Maximiliano S

    2015-06-01

    Advantages and disadvantages of using intermediate layers underneath resin-composite restorations have been presented under different perspectives. Yet, few long-term clinical studies evaluated the effect of glass-ionomer bases on restoration survival. The present study investigated the influence of glass-ionomer-cement base in survival of posterior composite restorations, compared to restorations without base. Original datasets of one dental practice were used to retrieve data retrospectively. The presence or absence of an intermediate layer of glass-ionomer-cement was the main factor under analysis, considering survival, annual failure rate and types of failure as outcomes. Other investigated factors were: patient gender, jaw, tooth, number of restored surfaces and composite. Statistical analysis was performed using Fisher's exact test, Kaplan-Meier method and multivariate Cox-regression. In total 632 restorations in 97 patients were investigated. Annual failure rates percentages up to 18-years were 1.9% and 2.1% for restorations with and without base, respectively. In restorations with glass-ionomer-cement base, fracture was the predominant reason for failure, corresponding to 57.8% of total failures. Failure type distribution was different (p=0.007) comparing restorations with and without base, but no effect in the overall survival of restorations was found (p=0.313). The presence of a glass-ionomer-cement base did not affect the survival of resin-composite restorations in the investigated sample. Acceptable annual failure rates after 18-years can be achieved with both techniques, leading to the perspective that an intermediate layer, placed during an interim treatment, may be maintained without clinical detriment, but no improvement in survival should be expected based on such measure. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

    Huang, Xiaoming; Yu, Guang; Wu, Chenfei

    2017-11-01

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

  12. Deployment strategy for battery energy storage system in distribution network based on voltage violation regulation

    Science.gov (United States)

    Wu, H.; Zhou, L.; Xu, T.; Fang, W. L.; He, W. G.; Liu, H. M.

    2017-11-01

    In order to improve the situation of voltage violation caused by the grid-connection of photovoltaic (PV) system in a distribution network, a bi-level programming model is proposed for battery energy storage system (BESS) deployment. The objective function of inner level programming is to minimize voltage violation, with the power of PV and BESS as the variables. The objective function of outer level programming is to minimize the comprehensive function originated from inner layer programming and all the BESS operating parameters, with the capacity and rated power of BESS as the variables. The differential evolution (DE) algorithm is applied to solve the model. Based on distribution network operation scenarios with photovoltaic generation under multiple alternative output modes, the simulation results of IEEE 33-bus system prove that the deployment strategy of BESS proposed in this paper is well adapted to voltage violation regulation invariable distribution network operation scenarios. It contributes to regulating voltage violation in distribution network, as well as to improve the utilization of PV systems.

  13. TLBO based Voltage Stable Environment Friendly Economic Dispatch Considering Real and Reactive Power Constraints

    Science.gov (United States)

    Verma, H. K.; Mafidar, P.

    2013-09-01

    In view of growing concern towards environment, power system engineers are forced to generate quality green energy. Hence the economic dispatch (ED) aims at the power generation to meet the load demand at minimum fuel cost with environmental and voltage constraints along with essential constraints on real and reactive power. The emission control which reduces the negative impact on environment is achieved by including the additional constraints in ED problem. Presently, the power system mostly operates near its stability limits, therefore with increased demand the system faces voltage problem. The bus voltages are brought within limit in the present work by placement of static var compensator (SVC) at weak bus which is identified from bus participation factor. The optimal size of SVC is determined by univariate search method. This paper presents the use of Teaching Learning based Optimization (TLBO) algorithm for voltage stable environment friendly ED problem with real and reactive power constraints. The computational effectiveness of TLBO is established through test results over particle swarm optimization (PSO) and Big Bang-Big Crunch (BB-BC) algorithms for the ED problem.

  14. WECS Based Self-Excited Squirrel-Cage Induction Generator with Reduced Voltage Source Inverter Rating

    Directory of Open Access Journals (Sweden)

    O.Chandra sekha

    2014-07-01

    Full Text Available This paper presents the regulation of the voltage and frequency of a stand-alone fixed-pitch wind energy conversion system (WECS based on a self-excited squirrel-cage induction machine. A shunt connected voltage source inverter (VSI and a controllable dump load are used for regulation purposes. A battery bank is included in the dc side of the VSI so that it can absorb and inject active power thus increasing the efficiency and availability of the system. A control scheme for the VSI with self-governing control of real and reactive power allows the state of charge of the batteries to be kept in a safe range while maximizing the voltage regulating capabilities of the VSI. The characteristics of the wind turbine, selfexcited generator, and the ratings of the VSI are considered in order to find out the load range for which voltage and frequency can be regulated for a given wind speed range. The possibility of the proposed system is verified by MATLAB/SIMULINK. simulations.

  15. Reasons for Placement and Replacement of Resin-based Composite Restorations in Greece

    Directory of Open Access Journals (Sweden)

    Nikolaos Andreas Chrysanthakopoulos

    2011-09-01

    Full Text Available Background and aims. The purpose of this investigation was to assess the placement and replacement of resin-based composite restorations and related factors in a private practice in Greece. Materials and methods. The study included 1500 subjects, 720 males and 780 females, aged 18 to 52 years old. The clinical examination involved calculation of the number of teeth with primary caries and failed-restored teeth. In addition the relationship between placed and replaced composite restorations and the following aspects was assessed: gender, cavity type, tooth type and evaluation of longevity of the replaced composite restorations. Statistical analysis performed using the chi-square test. A p value less than 5% was considered statistically significant. Results. The total number of restorations placed were 1940; 1202 of those (62% were placed for first time while 738 (38% were replaced. The main reason for the placement of new composite resin restorations was primary caries (60%, while secondary caries was the most frequent reason for the replacement (48% of those. A statistically significant difference was recorded between males and females regarding the composite restorations placed and replaced (p = 0.00082, the type of cavity of placed restorations (p = 0.00062, and the type of cavity of replaced ones (p = 0.00038. The median longevity of the replaced resin composite restorations was approximately 4 years (47%. Conclusion. Dental caries, primary and secondary, followed by tooth discoloration and loss of filling were the main reasons for placed and replaced composite restorations.

  16. Analysis of bi-directional piezoelectric-based converters for zero-voltage switching operation

    DEFF Research Database (Denmark)

    Ekhtiari, Marzieh; Zhang, Zhe; Andersen, Michael A. E.

    2016-01-01

    -directional piezoelectric power converter is a difficult task. However, the analysis in this work will be convenient for overcoming this challenge. The analysis defines the zero-voltage region indicating the operating points whether or not soft switching can be met over the switching frequency and load range. For the first...... time, a comprehensive analysis is provided, which can be used as a design guideline for applying control techniques in order to drive switches in piezoelectric transformer-based converters. This study further conveys the proposed method to the region where all the switches can obtain soft switching......This paper deals with a thorough analysis of zerovoltage switching especially for bi-directional, inductorless, piezoelectric transformer-based switch-mode power supplies with a half-bridge topology. Practically, obtaining zero-voltage switching for all of the switches in a bi...

  17. Passivity-Based Control of a Doubly Fed Induction Generator System under Unbalanced Grid Voltage Conditions

    Directory of Open Access Journals (Sweden)

    Jiawei Huang

    2017-08-01

    Full Text Available According to the theory of passivity-based control (PBC, this paper establishes a port-controlled Hamiltonian system with dissipation (PCHD model for a doubly fed induction generator (DFIG system under unbalanced grid voltage conditions and proposes a method of interconnection and damping assignment passivity-based control (IDA-PBC of the system under such conditions. By using this method, the rotor-side converter and grid-side converter can be controlled simultaneously in order to improve fault ride-through capability of the DFIG system. Simulation results indicate that this IDA-PBC strategy effectively suppresses fluctuations of output current and power in the DFIG system during unbalanced grid voltage sag/swell, enhances dynamic performance, and improves the robustness of the system.

  18. FPGA Techniques Based New Hybrid Modulation Strategies for Voltage Source Inverters

    Directory of Open Access Journals (Sweden)

    L. U. Sudha

    2015-01-01

    Full Text Available This paper corroborates three different hybrid modulation strategies suitable for single-phase voltage source inverter. The proposed method is formulated using fundamental switching and carrier based pulse width modulation methods. The main tale of this proposed method is to optimize a specific performance criterion, such as minimization of the total harmonic distortion (THD, lower order harmonics, switching losses, and heat losses. The proposed method is articulated using fundamental switching and carrier based pulse width modulation methods. Thus, the harmonic pollution in the power system will be reduced and the power quality will be augmented with better harmonic profile for a target fundamental output voltage. The proposed modulation strategies are simulated in MATLAB r2010a and implemented in a Xilinx spartan 3E-500 FG 320 FPGA processor. The feasibility of these modulation strategies is authenticated through simulation and experimental results.

  19. FPGA techniques based new hybrid modulation strategies for voltage source inverters.

    Science.gov (United States)

    Sudha, L U; Baskaran, J; Elankurisil, S A

    2015-01-01

    This paper corroborates three different hybrid modulation strategies suitable for single-phase voltage source inverter. The proposed method is formulated using fundamental switching and carrier based pulse width modulation methods. The main tale of this proposed method is to optimize a specific performance criterion, such as minimization of the total harmonic distortion (THD), lower order harmonics, switching losses, and heat losses. The proposed method is articulated using fundamental switching and carrier based pulse width modulation methods. Thus, the harmonic pollution in the power system will be reduced and the power quality will be augmented with better harmonic profile for a target fundamental output voltage. The proposed modulation strategies are simulated in MATLAB r2010a and implemented in a Xilinx spartan 3E-500 FG 320 FPGA processor. The feasibility of these modulation strategies is authenticated through simulation and experimental results.

  20. A practice-based research network on the survival of ceramic inlay/onlay restorations.

    Science.gov (United States)

    Collares, Kauê; Corrêa, Marcos B; Laske, Mark; Kramer, Enno; Reiss, Bernd; Moraes, Rafael R; Huysmans, Marie-Charlotte D N J M; Opdam, Niek J M

    2016-05-01

    To evaluate prospectively the longevity of ceramic inlay/onlay restorations placed in a web-based practice-based research network and to investigate risk factors associated with restoration failures. Data were collected by a practice-based research network called Ceramic Success Analysis (CSA). 5791 inlay/onlay ceramic restorations were placed in 5523 patients by 167 dentists between 1994 and 2014 in their dental practices. For each restoration specific information related to the tooth, procedures and materials used were recorded. Annual failure rates (AFRs) were calculated and variables associated with failure were assessed by a multivariate Cox-regression analysis with shared frailty. The mean observation time was 3 years (maximum 15 years) of clinical service, and AFRs at 3 and 10 years follow up were calculated as 1.0% and 1.6%. Restorations with cervical outline in dentin showed a 78% higher risk for failure compared to restorations with margins in enamel. The presence of a liner or base of glass-ionomer cement resulted in a risk for failure twice as large as that of restorations without liner or base material. Restorations performed with simplified adhesive systems (2-step etch-and-rinse and 1-step self-etch) presented a risk of failure 142% higher than restorations performed with adhesives with bonding resin as a separate step (3-step etch-and-rinse and 2-step self-etch). 220 failures were recorded and the most predominant reason for failure was fracture of the restoration or tooth (44.5%). Ceramic inlay/onlay restorations made from several glass ceramic materials and applied by a large number of dentists showed a good survival. Deep cervical cavity outline, presence of a glass ionomer lining cement, and use of simplified adhesive systems were risk factors for survival. Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  1. Analysis of the Vibration Spectrum Based on the Input Voltage Spectrum

    OpenAIRE

    Mathe, Laszlo; Jakobsen, Uffe; Rasmussen, Peter Omand; Pedersen, John Kim

    2009-01-01

    Pulse width modulation, present in most drives, gives rise to harmonics in the current and this generates radial forces that cause vibrations in the motor shell. This paper derives an analytical expression for the estimation of the spectrum of the radial force in a machine with an air gap, based on the spectrum of the applied voltage. The measurements show that the spectral components are caused mainly by the modulation, which agrees with the results from the analytical solution. A method...

  2. A multi-GHz chaotic optoelectronic oscillator based on laser terminal voltage

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C. Y., E-mail: cychang@gatech.edu [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0250 (United States); UMI 2958 Georgia Tech-CNRS, Georgia Tech Lorraine, 2 Rue Marconi, F-57070 Metz (France); Choi, Daeyoung; Locquet, A., E-mail: alexandre@gatech.edu; Wishon, Michael J.; Citrin, D. S., E-mail: david.citrin@ece.gatech.edu [UMI 2958 Georgia Tech-CNRS, Georgia Tech Lorraine, 2 Rue Marconi, F-57070 Metz (France); School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0250 (United States); Merghem, K.; Ramdane, Abderrahim; Martinez, A. [Laboratory for Photonics and Nanostructures, CNRS, Route de Nozay, 91460 Marcoussis (France); Lelarge, François [Laboratory for Photonics and Nanostructures, CNRS, Route de Nozay, 91460 Marcoussis (France); III-V Lab, A Joint Laboratory of Alcatel Lucent Bell Labs and Thales Research and Technology and CEA-LETI, Route de Nozay, 91460 Marcoussis (France)

    2016-05-09

    A multi-GHz chaotic optoelectronic oscillator based on an external cavity semiconductor laser (ECL) is demonstrated. Unlike the standard optoelectronic oscillators for microwave applications, we do not employ the dynamic light output incident on a photodiode to generate the microwave signal, but instead generate the microwave signal directly by measuring the terminal voltage V(t) of the laser diode of the ECL under constant-current operation, thus obviating the photodiode entirely.

  3. Dynamic Consensus Algorithm based Distributed Voltage Harmonic Compensation in Islanded Microgrids

    DEFF Research Database (Denmark)

    Meng, Lexuan; Tang, Fen; Firoozabadi, Mehdi Savaghebi

    2015-01-01

    In islanded microgrids, the existence of nonlinear electric loads may cause voltage distortion and affect the performance of power quality sensitive equipment. Thanks to the prevalent utilization of interfacing power electronic devices and information/communication technologies, distributed...... generators can be employed as compensators to enhance the power quality on consumer side. However, conventional centralized control is facing obstacles because of the distributed fashion of generation and consumption. Accordingly, this paper proposes a consensus algorithm based distributed hierarchical...

  4. Performance Analysis of a Voltage Source Converter (VSC based HVDC Transmission System under Faulted Conditions

    Directory of Open Access Journals (Sweden)

    Amiri RABIE

    2009-12-01

    Full Text Available Voltage Source Converter (VSC based HVDC transmission technology hasbeen selected as the basis for several recent projects due to its controllability,compact modular design, ease of system interface, and low environmentalimpact. This paper investigates the dynamic performance of a 200MW,±100kV VSC-HVDC transmission system under some faulted conditionsusing MATLAB/Simulink. Simulation results confirm the satisfactoryperformance of the proposed system under active and reactive powervariations and fault conditions.

  5. Location-based restoration mechanism for multi-domain GMPLS networks

    DEFF Research Database (Denmark)

    Manolova, Anna Vasileva; Calle, Eusibi; Ruepp, Sarah Renée

    2009-01-01

    In this paper we propose and evaluate the efficiency of a location-based restoration mechanism in a dynamic multi-domain GMPLS network. We focus on inter-domain link failures and utilize the correlation between the actual position of a failed link along the path with the applied restoration...... technique. Our results show, that without violating the strong privacy preservation requirements between domains, the proposed mechanism has improved performance in terms of successfully restored connections compared to the traditional local-to-egress and end-to-end restoration approaches. Furthermore...

  6. Containment and Consensus-based Distributed Coordination Control for Voltage Bound and Reactive Power Sharing in AC Microgrid

    DEFF Research Database (Denmark)

    Han, Renke; Meng, Lexuan; Ferrari-Trecate, Giancarlo

    2017-01-01

    This paper offers a highly flexible and reliable control strategy to achieve voltage bounded regulation and accurate reactive power sharing coordinately in AC Micro-Grids. A containment and consensus-based distributed coordination controller is proposed, by which each output voltage magnitude can...

  7. 18-year survival of posterior composite resin restorations with and without glass ionomer cement as base.

    NARCIS (Netherlands)

    Sande, F.H. van de; Rosa Rodolpho, P.A. Da; Basso, G.R.; Patias, R.; Rosa, Q.F. da; Demarco, F.F.; Opdam, N.J.M.; Cenci, M.S.

    2015-01-01

    OBJECTIVE: Advantages and disadvantages of using intermediate layers underneath resin-composite restorations have been presented under different perspectives. Yet, few long-term clinical studies evaluated the effect of glass-ionomer bases on restoration survival. The present study investigated the

  8. An inventory of continental U.S. terrestrial candidate ecological restoration areas based on landscape context

    Science.gov (United States)

    Landscape context is an important factor in restoration ecology, but the use of landscape context for site prioritization has not been as fully developed. We used morphological image processing to identify candidate ecological restoration areas based on their proximity to existin...

  9. Repair may increase survival of direct posterior restorations - A practice based study

    NARCIS (Netherlands)

    Casagrande, L.; Laske, M.; Bronkhorst, E.M.; Huysmans, M.C.D.N.J.M.; Opdam, N.J.M.

    2017-01-01

    OBJECTIVES: To investigate repairs of direct restorations by a group of Dutch general dental practitioners (GDPs) and its consequences on longevity of restorations. METHODS: Data set was based on dental records of patients attending 11 general dental practices (24 Dentists) in the Netherlands.

  10. An Impedance-Based Stability Analysis Method for Paralleled Voltage Source Converters

    DEFF Research Database (Denmark)

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

    2014-01-01

    is assessed based on a series of Nyquist diagrams drawn for the terminal impedance of each converter. Thus, the effect of the right half-plane zeros of terminal impedances in the derivation of impedance ratio for paralleled source-source converters is avoided. The interaction between the terminal impedance......This paper analyses the stability of paralleled voltage source converters in AC distributed power systems. An impedance-based stability analysis method is presented based on the Nyquist criterion for multiloop system. Instead of deriving the impedance ratio as usual, the system stability...

  11. Monotonic transition based forward body bias for dual threshold voltage low power embedded processors

    Directory of Open Access Journals (Sweden)

    S. Jayapal

    2006-01-01

    Full Text Available Dual threshold voltage and forward body bias techniques are effective ways to optimally balance the standby leakage power and performance. In this paper, we propose a novel fine-grained forward body biasing scheme for monotonic static logic circuits. In the proposed scheme, the forward body bias is applied to high threshold voltage of either the pull-up or the pull-down network based on the evaluation transition and the state of operation. This technique improves the low skew NAND and NOR circuit performance by 7% and 11%, high skew NAND and NOR by 8% and 13% respectively. It reduces both active and standby leakage power as compared to monotonic static CMOS with dual-VT technique. The simulations are carried out using 130 nm mixed mode process technology to validate our proposed technique.

  12. Partial shadowing detection based on equivalent thermal voltage monitoring for PV module diagnostics

    DEFF Research Database (Denmark)

    Sera, Dezso; Teodorescu, Remus; Rodriguez, Pedro

    2009-01-01

    Partial shadowing of photovoltaic systems can overproportionally reduce the energy yield and lead to early ageing and failure of the shadowed cells. Large area shadows are relatively easy to detect due to the eminent power reduction and decrease of fill factor. However, small area partial shadows...... in a larger system do not have a very obvious effect on the output power or fill factor of the PV array and can remain undetected, leading to failure. In this paper a method for detecting small area partial shadows, based on equivalent thermal voltage, is presented. A simplified expression of the equivalent...... thermal voltage is proposed, which increases the robustness against measurement errors and model limitations at low irradiation conditions. Experimental results confirm the high sensitivity of the method even to a relatively small area shadow, while showing very good robustness against increase in series...

  13. Voltage stability index based optimal placement of static VAR compensator and sizing using Cuckoo search algorithm

    Science.gov (United States)

    Venkateswara Rao, B.; Kumar, G. V. Nagesh; Chowdary, D. Deepak; Bharathi, M. Aruna; Patra, Stutee

    2017-07-01

    This paper furnish the new Metaheuristic algorithm called Cuckoo Search Algorithm (CSA) for solving optimal power flow (OPF) problem with minimization of real power generation cost. The CSA is found to be the most efficient algorithm for solving single objective optimal power flow problems. The CSA performance is tested on IEEE 57 bus test system with real power generation cost minimization as objective function. Static VAR Compensator (SVC) is one of the best shunt connected device in the Flexible Alternating Current Transmission System (FACTS) family. It has capable of controlling the voltage magnitudes of buses by injecting the reactive power to system. In this paper SVC is integrated in CSA based Optimal Power Flow to optimize the real power generation cost. SVC is used to improve the voltage profile of the system. CSA gives better results as compared to genetic algorithm (GA) in both without and with SVC conditions.

  14. Dragon-I injector based on the induction voltage adder technique

    Directory of Open Access Journals (Sweden)

    Zhang Kaizhi

    2006-08-01

    Full Text Available The Dragon-I injector based on the induction voltage adder technique is introduced. Twelve ferrite loaded induction cells are connected in a series through central conducting stalks to achieve a pulsed voltage higher than 3.5 MV across the diode. Electrons are extracted from the velvet emitter and guided through the anode pipe by the magnets placed inside the cathode and anode shrouds. Measurements at the exit of injector show that, with an electric field of 200  kV/cm near the velvet surface and suitable magnetic field distribution, an electron beam up to 2.8 kA can be obtained with a normalized emittance of 1040π   mm mrad, and energy spread of 2.1% (3σ around the central energy of 3.5 MeV.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-09-15

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

  16. Low Voltage Floating Gate MOS Transistor Based Four-Quadrant Multiplier

    Directory of Open Access Journals (Sweden)

    R. Srivastava

    2014-12-01

    Full Text Available This paper presents a four-quadrant multiplier based on square-law characteristic of floating gate MOSFET (FGMOS in saturation region. The proposed circuit uses square-difference identity and the differential voltage squarer proposed by Gupta et al. to implement the multiplication function. The proposed multiplier employs eight FGMOS transistors and two resistors only. The FGMOS implementation of the multiplier allows low voltage operation, reduced power consumption and minimum transistor count. The second order effects caused due to mobility degradation, component mismatch and temperature variations are discussed. Performance of the proposed circuit is verified at ±0.75 V in TSMC 0.18 µm CMOS, BSIM3 and Level 49 technology by using Cadence Spectre simulator.

  17. Coordinated Control Strategies of VSC-HVDC-Based Wind Power Systems for Low Voltage Ride Through

    Directory of Open Access Journals (Sweden)

    Xinyin Zhang

    2015-07-01

    Full Text Available The Voltage Source Converter-HVDC (VSC-HVDC system applied to wind power generation can solve large scale wind farm grid-connection and long distance transmission problems. However, the low voltage ride through (LVRT of the VSC-HVDC connected wind farm is a key technology issue that must be solved, and it is currently lacking an economic and effective solution. In this paper, a LVRT coordinated control strategy is proposed for the VSC-HVDC-based wind power system. In this strategy, the operation and control of VSC-HVDC and wind farm during the grid fault period is improved. The VSC-HVDC system not only provides reactive power support to the grid, but also effectively maintains the power balance and DC voltage stability by reducing wind-farm power output, without increasing the equipment investment. Correspondingly, to eliminate the influence on permanent magnet synchronous generator (PMSG-based wind turbine (WT systems, a hierarchical control strategy is designed. The speed and validity of the proposed LVRT coordinated control strategy and hierarchical control strategy were verified by MATLAB/Simulink simulations.

  18. Ultra-Low-Voltage CMOS-Based Current Bleeding Mixer with High LO-RF Isolation

    Directory of Open Access Journals (Sweden)

    Gim Heng Tan

    2014-01-01

    Full Text Available This journal presents an ultra-low-voltage current bleeding mixer with high LO-RF port-to-port isolation, implemented on 0.13 μm standard CMOS technology for ZigBee application. The architecture compliments a modified current bleeding topology, consisting of NMOS-based current bleeding transistor, PMOS-based switching stage, and integrated inductors achieving low-voltage operation and high LO-RF isolation. The mixer exhibits a conversion gain of 7.5 dB at the radio frequency (RF of 2.4 GHz, an input third-order intercept point (IIP3 of 1 dBm, and a LO-RF isolation measured to 60 dB. The DC power consumption is 572 µW at supply voltage of 0.45 V, while consuming a chip area of 0.97 × 0.88 mm2.

  19. Determination of the aging offset voltage of AMR sensors based on accelerated degradation test

    NARCIS (Netherlands)

    Zambrano Constantini, A.C.; Kerkhoff, Hans G.

    Usually Anisotropic Magnetoresistance angle sensors are configured with two Wheatstone bridges, but an undesirable offset voltage included in the sensor output affects its accuracy. The total offset voltage combines a voltage due to resistance mismatches during manufacturing and a voltage from

  20. Agreement among dentists' restorative treatment planning thresholds for primary occlusal caries, primary proximal caries, and existing restorations: findings from The National Dental Practice-Based Research Network.

    Science.gov (United States)

    Heaven, Tim J; Gordan, Valeria V; Litaker, Mark S; Fellows, Jeffrey L; Brad Rindal, D; Firestone, Allen R; Gilbert, Gregg H

    2013-08-01

    The aim of this study was to quantify the agreement among individual National Dental Practice-Based Research Network dentists' self-reported treatment decisions for primary occlusal caries, primary proximal caries, and existing restorations. Five hypothetical clinical scenarios were presented: primary occlusal caries; primary proximal caries; and whether three existing restorations should be repaired or replaced. We quantified the probability that dentists who recommended later restorative intervention for primary caries were the same ones who recommended that existing restorations be repaired instead of replaced. Dentists who recommended later restorative treatment of primary occlusal caries and proximal caries at a more-advanced stage were significantly more likely to recommend repair instead of replacement. Agreement among dentists on a threshold stage for the treatment of primary caries ranged from 40 to 68%, while that for repair or replacement of existing restorations was 36 to 43%. Dentists who recommended repair rather than replacement of existing restorations were significantly more likely to recommend later treatment of primary caries. Conversely, dentists who recommended treatment of primary caries at an earlier stage were significantly more likely to recommend replacement of the entire restoration. Between-dentist agreement for primary caries treatment was better than between-dentist agreement for repair or replacement of existing restorations. These findings suggest consistency in how individual dentists approach the treatment of primary caries and existing restorations. However, substantial variation was found between dentists in their treatment decisions about the same teeth. Copyright © 2013 Elsevier Ltd. All rights reserved.

  1. Agreement among dentists’ restorative treatment planning thresholds for primary occlusal caries, primary proximal caries, and existing restorations: Findings from The National Dental Practice-Based Research Network

    Science.gov (United States)

    Heaven, Tim J.; Gordan, Valeria V.; Litaker, Mark S.; Fellows, Jeffrey L.; Rindal, D. Brad; Firestone, Allen R.; Gilbert, Gregg H.

    2013-01-01

    Objectives The aim of this study was to quantify the agreement among individual National Dental Practice-Based Research Network dentists’ self-reported treatment decisions for primary occlusal caries, primary proximal caries, and existing restorations. Methods Five hypothetical clinical scenarios were presented: primary occlusal caries; primary proximal caries; and whether three existing restorations should be repaired or replaced. We quantified the probability that dentists who recommended later restorative intervention for primary caries were the same ones who recommended that existing restorations be repaired instead of replaced. Results Dentists who recommended later restorative treatment of primary occlusal caries and proximal caries at a more-advanced stage were significantly more likely to recommend repair instead of replacement. Agreement among dentists on a threshold stage for the treatment of primary caries ranged from 40 to 68%, while that for repair or replacement of existing restorations was 36 to 43%. Conclusions Dentists who recommended repair rather than replacement of existing restorations were significantly more likely to recommend later treatment of primary caries. Conversely, dentists who recommended treatment of primary caries at an earlier stage were significantly more likely to recommend replacement of the entire restoration. Between-dentist agreement for primary caries treatment was better than between-dentist agreement for repair or replacement of existing restorations. Clinical implications These findings suggest consistency in how individual dentists approach the treatment of primary caries and existing restorations. However, substantial variation was found between dentists in their treatment decisions about the same teeth. PMID:23743181

  2. Design and Quasi-Equilibrium Analysis of a Distributed Frequency-Restoration Controller for Inverter-Based Microgrids

    Energy Technology Data Exchange (ETDEWEB)

    Ainsworth, Nathan G [ORNL; Grijalva, Prof. Santiago [Georgia Institute of Technology, Atlanta

    2013-01-01

    This paper discusses a proposed frequency restoration controller which operates as an outer loop to frequency droop for voltage-source inverters. By quasi-equilibrium analysis, we show that the proposed controller is able to provide arbitrarily small steady-state frequency error while maintaing power sharing between inverters without need for communication or centralized control. We derive rate of convergence, discuss design considerations (including a fundamental trade-off that must be made in design), present a design procedure to meet a maximum frequency error requirement, and show simulation results verifying our analysis and design method. The proposed controller will allow flexible plug-and-play inverter-based networks to meet a specified maximum frequency error requirement.

  3. Design of the robust synchronous generator stator voltage regulator based on the interval plant model

    Directory of Open Access Journals (Sweden)

    Stojić Đorđe

    2013-01-01

    Full Text Available In this paper a novel method for the stator voltage regulator of a synchronous generator based on the interval plant mode, is presented. Namely, it is shown in the literature that, in order to design a controller for the first-order compensator, the limited number of interval plants needs to be examined. Consequently, the intervals of the plant model parameter variations used to calculate the four extreme interval plants required for the sequential PI controller design are determined. The controller is designed using frequency-domain-based techniques, while its robust performance is examined using simulation tests.

  4. Virtual-Impedance-Based Control for Voltage-Source and Current-Source Converters

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Li, YunWei; Blaabjerg, Frede

    2015-01-01

    The virtual impedance concept is increasingly used for the control of power electronic systems. Generally, the virtual impedance loop can either be embedded as an additional degree of freedom for active stabilization and disturbance rejection, or be employed as a command reference generator...... for the converters to provide ancillary services. This paper presents an overview of the virtual-impedance-based control strategies for voltage-source and current-source converters. The control output impedance shaping attained by the virtual impedances is generalized first using the impedance-based models...

  5. Performance Evaluation of Three Different Inverter Configurations of DVR for Mitigation of Voltage Events

    Directory of Open Access Journals (Sweden)

    Miska Prasad

    2016-12-01

    Full Text Available The voltage events namely voltage sags and voltage swells represent the most common, frequent and important power quality events in today’s power system. Dynamic voltage restorer (DVR is one of the key components used to mitigate the supply voltage quality disturbances in terms of voltage sags and swells in the distribution system. It consists of an energy storage unit, a voltage source inverter, a filter, a coupling transformer and the control system. This paper presents three different inverter configurations of dynamic voltage restorer (DVR for mitigation of voltage events such as voltage sags and swells with sudden addition or removal of the nonlinear load. These three configurations are voltage source inverter based DVR (VSI-DVR, current source inverter based DVR (CSI-DVR and impedance or Z-source inverter based DVR (ZSI-DVR. The d-q control technique is used to control the operation of the DVR. The response of ZSI-DVR for mitigation of voltage sags and swells are investigated and compared with VSI-DVR and CSI-DVR using MATLAB/SIMULINK environment.

  6. Public magnetic field exposure based on internal current density for electric low voltage systems.

    Science.gov (United States)

    Keikko, Tommi; Seesvuori, Reino; Hyvönen, Martti; Valkealahti, Seppo

    2009-04-01

    A measurement concept utilizing a new magnetic field exposure metering system has been developed for indoor substations where voltage is transformed from a medium voltage of 10 or 20 kV to a low voltage of 400 V. The new metering system follows the guidelines published by the International Commission on Non-Ionizing Radiation Protection. It can be used to measure magnetic field values, total harmonic distortion of the magnetic field, magnetic field exposure ratios for public and workers, load current values, and total harmonic distortion of the load current. This paper demonstrates how exposure to non-sinusoidal magnetic fields and magnetic flux density exposure values can be compared directly with limit values for internal current densities in a human body. Further, we present how the magnetic field and magnetic field exposure behaves in the vicinity of magnetic field sources within the indoor substation and in the neighborhood. Measured magnetic fields around the substation components have been used to develop a measurement concept by which long-term measurements in the substations were performed. Long-term measurements revealed interesting and partly unexpected dependencies between the measured quantities, which have been further analyzed. The principle of this paper is to substitute a demanding exposure measurement with measurements of the basic quantities like the 50 Hz fundamental magnetic field component, which can be estimated based on the load currents for certain classes of substation lay-out.

  7. A compact high-voltage pulse generator based on pulse transformer with closed magnetic core.

    Science.gov (United States)

    Zhang, Yu; Liu, Jinliang; Cheng, Xinbing; Bai, Guoqiang; Zhang, Hongbo; Feng, Jiahuai; Liang, Bo

    2010-03-01

    A compact high-voltage nanosecond pulse generator, based on a pulse transformer with a closed magnetic core, is presented in this paper. The pulse generator consists of a miniaturized pulse transformer, a curled parallel strip pulse forming line (PFL), a spark gap, and a matched load. The innovative design is characterized by the compact structure of the transformer and the curled strip PFL. A new structure of transformer windings was designed to keep good insulation and decrease distributed capacitance between turns of windings. A three-copper-strip structure was adopted to avoid asymmetric coupling of the curled strip PFL. When the 31 microF primary capacitor is charged to 2 kV, the pulse transformer can charge the PFL to 165 kV, and the 3.5 ohm matched load can deliver a high-voltage pulse with a duration of 9 ns, amplitude of 84 kV, and rise time of 5.1 ns. When the load is changed to 50 ohms, the output peak voltage of the generator can be 165 kV, the full width at half maximum is 68 ns, and the rise time is 6.5 ns.

  8. Entropy-Based Voltage Fault Diagnosis of Battery Systems for Electric Vehicles

    Directory of Open Access Journals (Sweden)

    Peng Liu

    2018-01-01

    Full Text Available The battery is a key component and the major fault source in electric vehicles (EVs. Ensuring power battery safety is of great significance to make the diagnosis more effective and predict the occurrence of faults, for the power battery is one of the core technologies of EVs. This paper proposes a voltage fault diagnosis detection mechanism using entropy theory which is demonstrated in an EV with a multiple-cell battery system during an actual operation situation. The preliminary analysis, after collecting and preprocessing the typical data periods from Operation Service and Management Center for Electric Vehicle (OSMC-EV in Beijing, shows that overvoltage fault for Li-ion batteries cell can be observed from the voltage curves. To further locate abnormal cells and predict faults, an entropy weight method is established to calculate the objective weight, which reduces the subjectivity and improves the reliability. The result clearly identifies the abnormity of cell voltage. The proposed diagnostic model can be used for EV real-time diagnosis without laboratory testing methods. It is more effective than traditional methods based on contrastive analysis.

  9. Optimal Design of a Resonance-Based Voltage Boosting Rectifier for Wireless Power Transmission.

    Science.gov (United States)

    Lim, Jaemyung; Lee, Byunghun; Ghovanloo, Maysam

    2018-02-01

    This paper presents the design procedure for a new multi-cycle resonance-based voltage boosting rectifier (MCRR) capable of delivering a desired amount of power to the load (PDL) at a designated high voltage (HV) through a loosely-coupled inductive link. This is achieved by shorting the receiver (Rx) LC-tank for several cycles to harvest and accumulate the wireless energy in the RX inductor before boosting the voltage by breaking the loop and transferring the energy to the load in a quarter cycle. By optimizing the geometries of the transmitter (Tx) and Rx coils and the number of cycles, N, for energy harvesting, through an iterative design procedure, the MCRR can achieve the highest PDL under a given set of design constraints. Governing equations in the MCRR operation are derived to identify key specifications and the design guidelines. Using an exemplary set of specs, the optimized MCRR was able to generate 20.9 VDC across a 100 kΩ load from a 1.8 Vp, 6.78 MHz sinusoid input in the ISM-band at a Tx/Rx coil separation of 1.3 cm, power transfer efficiency (PTE) of 2.2%, and N = 9 cycles. At the same coil distance and loading, coils optimized for a conventional half-wave rectifier (CHWR) were able to reach only 13.6 VDC from the same source.

  10. Fractographic features of glass-ceramic and zirconia-based dental restorations fractured during clinical function

    Science.gov (United States)

    Øilo, Marit; Hardang, Anne D; Ulsund, Amanda H; Gjerdet, Nils R

    2014-01-01

    Fractures during clinical function have been reported as the major concern associated with all-ceramic dental restorations. The aim of this study was to analyze the fracture features of glass-ceramic and zirconia-based restorations fractured during clinical use. Twenty-seven crowns and onlays were supplied by dentists and dental technicians with information about type of cement and time in function, if available. Fourteen lithium disilicate glass-ceramic restorations and 13 zirconia-based restorations were retrieved and analyzed. Fractographic features were examined using optical microscopy to determine crack initiation and crack propagation of the restorations. The material comprised fractured restorations from one canine, 10 incisors, four premolars, and 11 molars. One crown was not categorized because of difficulty in orientation of the fragments. The results revealed that all core and veneer fractures initiated in the cervical margin and usually from the approximal area close to the most coronally placed curvature of the margin. Three cases of occlusal chipping were found. The margin of dental all-ceramic single-tooth restorations was the area of fracture origin. The fracture features were similar for zirconia, glass-ceramic, and alumina single-tooth restorations. Design features seem to be of great importance for fracture initiation. PMID:24698173

  11. Fractographic features of glass-ceramic and zirconia-based dental restorations fractured during clinical function.

    Science.gov (United States)

    Oilo, Marit; Hardang, Anne D; Ulsund, Amanda H; Gjerdet, Nils R

    2014-06-01

    Fractures during clinical function have been reported as the major concern associated with all-ceramic dental restorations. The aim of this study was to analyze the fracture features of glass-ceramic and zirconia-based restorations fractured during clinical use. Twenty-seven crowns and onlays were supplied by dentists and dental technicians with information about type of cement and time in function, if available. Fourteen lithium disilicate glass-ceramic restorations and 13 zirconia-based restorations were retrieved and analyzed. Fractographic features were examined using optical microscopy to determine crack initiation and crack propagation of the restorations. The material comprised fractured restorations from one canine, 10 incisors, four premolars, and 11 molars. One crown was not categorized because of difficulty in orientation of the fragments. The results revealed that all core and veneer fractures initiated in the cervical margin and usually from the approximal area close to the most coronally placed curvature of the margin. Three cases of occlusal chipping were found. The margin of dental all-ceramic single-tooth restorations was the area of fracture origin. The fracture features were similar for zirconia, glass-ceramic, and alumina single-tooth restorations. Design features seem to be of great importance for fracture initiation. © 2014 Eur J Oral Sci.

  12. Interactions Between Indirect DC-Voltage Estimation and Circulating Current Controllers of MMC-Based HVDC Transmission Systems

    DEFF Research Database (Denmark)

    Wickramasinghe, Harith R.; Konstantinou, Georgios; Pou, Josep

    2018-01-01

    Estimation-based indirect dc-voltage control in MMCs interacts with circulating current control methods. This paper proposes an estimation-based indirect dc-voltage control method for MMC-HVDC systems and analyzes its performance compared to alternative estimations. The interactions between......-state and transient performance is demonstrated using a benchmark MMC-HVDC transmission system, implemented in a real-time digital simulator. The results verify the theoretical evaluations and illustrate the operation and performance of the proposed indirect dc-voltage control method....

  13. Restoration of single image based on kernel estimation with L1-regularization method

    Science.gov (United States)

    Zhao, Minghua; Cao, Hui; Zhang, Xin; Shi, Zhenghao; Li, Peng

    2017-07-01

    Image restoration is a significant task in the fields of computer vision and image processing. Image restoration research consists of two aspects: kernel estimation and image restoration. A single image restoration method based on L1-regularized blur kernel estimation is proposed in this paper. First, a bilateral filter is used to remove the image noise effectively. Second, the improved shock filter is used to enhance the edge information of the image. Subsequently, L1-regularization method is used to estimate the blur kernel of the blurred image alternately, during which Split-Bregman algorithm is used to optimize the solution process. Finally, Hyper-Laplacian and sparse priors are applied to the image obtained from the non-blind deconvolution process. Experimental results show that compared to other methods, better restoration results as well as improved computational efficiency can be achieved with the proposed method.

  14. Optical properties of base dentin ceramics for all-ceramic restorations.

    OpenAIRE

    Shiraishi, Takanobu; Wood, Duncan J.; Shinozaki, Nobuya; Van Noort, Richard

    2011-01-01

    The study was conducted to compare the optical parameters of VM7(®) M-shade base dentin ceramics (VITA, Germany) for all ceramic restorations to the chemical composition across the 3D-MASTER(®) shade system.

  15. Modeling and Simulation of a Carrier-based PWM Voltage Source Inverter for a Nine Phase Induction Machine Drive

    National Research Council Canada - National Science Library

    Omonowo David Momoh

    2014-01-01

    ...; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;">The analysis of a carrier-based PWM two level voltage source inverter for a nine phase induction machine drive system is presented in this paper...

  16. Restoration of noncarious tooth defects by dentists in The Dental Practice-Based Research Network

    DEFF Research Database (Denmark)

    Nascimento, Marcelle M; Gordan, Valeria V; Qvist, Vibeke

    2011-01-01

    The authors conducted a study to quantify the reasons for restoring noncarious tooth defects (NCTDs) by dentists in The Dental Practice-Based Research Network (DPBRN) and to assess the tooth, patient and dentist characteristics associated with those reasons.......The authors conducted a study to quantify the reasons for restoring noncarious tooth defects (NCTDs) by dentists in The Dental Practice-Based Research Network (DPBRN) and to assess the tooth, patient and dentist characteristics associated with those reasons....

  17. Active Damping of LLCL-Filter Resonance Based on LC-Trap Voltage or Current Feedback

    DEFF Research Database (Denmark)

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

    2016-01-01

    , a high-pass damper must be used, which as commonly known, may cause undesired noise complications depending on operating conditions. In this paper, the same capacitor current damper has been investigated for LLCL-filter with its limitations clarified. Both cases of with and without delays have been...... considered. The investigation has also been extended to consider LC-trap voltage feedback, which based on the formulated transfer functions and experimental results, permits a simple proportional damper to be used. Lesser noise complications and faster dynamic can then be achieved. Circuit equivalences...

  18. On-state voltage drop based power limit detection of IGBT inverters

    DEFF Research Database (Denmark)

    Trintis, Ionut; Ghimire, Pramod; Munk-Nielsen, Stig

    2015-01-01

    insulated gate bipolar transistors (IGBTs) in the inverter, using advanced gate driver. The die temperature is estimated and monitored on each device during power converter operation. Based on the monitored temperature in real time, the maximum power capability is detected. The output power is increased......Power density is a key performance factor in order to reduce the cost and size of a power converter. Because of the unknown junction temperature, today’s design margins are relatively high to ensure safe and a reliable operation. In this paper, the on-state voltage drop is measured online for all...

  19. Novel Control for Voltage Boosted Matrix Converter based Wind Energy Conversion System with Practicality

    Science.gov (United States)

    Kumar, Vinod; Joshi, Raghuveer Raj; Yadav, Dinesh Kumar; Garg, Rahul Kumar

    2017-04-01

    This paper presents the implementation and investigation of novel voltage boosted matrix converter (MC) based permanent magnet wind energy conversion system (WECS). In this paper, on-line tuned adaptive fuzzy control algorithm cooperated with reversed MC is proposed to yield maximum energy. The control system is implemented on a dSPACE DS1104 real time board. Feasibility of the proposed system has been experimentally verified using a laboratory 1.2 kW prototype of WECS under steady-state and dynamic conditions.

  20. Effect of single walled carbon nanotubes on the threshold voltage of dye based photovoltaic devices

    Science.gov (United States)

    Chakraborty, S.; Manik, N. B.

    2016-01-01

    Carbon nanotubes are being widely used in organic photovoltaic (OPV) devices as their usage has been reported to enhance the device efficiency along with other related parameters. In this work we have studied the energy (Ec) effect of single walled carbon nanotubes (SWCNT) on the threshold voltage (Vth) and also on the trap states of dye based photovoltaic devices. SWCNT is added in a series of dyes such as Rose Bengal (RB), Methyl Red (MR), Malachite Green (MG) and Crystal Violet (CV). By analysing the steady state dark current-voltage (I-V) characteristics Vth and Ec is estimated for the different devices with and without addition of SWCNT. It is observed that on an average for all the dyes Vth is reduced by about 30% in presence of SWCNT. The trap energy Ec also reduces in case of all the dyes. The relation between Vth, Ec and total trap density is discussed. From the photovoltaic measurements it is seen that the different photovoltaic parameters change with addition of SWCNT to the dye based devices. Both the short circuit current density and fill factor are found to increase for all the dye based devices in presence of SWCNT.

  1. Structure-based assessment of disease-related mutations in human voltage-gated sodium channels

    Directory of Open Access Journals (Sweden)

    Weiyun Huang

    2017-02-01

    Full Text Available ABSTRACT Voltage-gated sodium (Nav channels are essential for the rapid upstroke of action potentials and the propagation of electrical signals in nerves and muscles. Defects of Nav channels are associated with a variety of channelopathies. More than 1000 disease-related mutations have been identified in Nav channels, with Nav1.1 and Nav1.5 each harboring more than 400 mutations. Nav channels represent major targets for a wide array of neurotoxins and drugs. Atomic structures of Nav channels are required to understand their function and disease mechanisms. The recently determined atomic structure of the rabbit voltage-gated calcium (Cav channel Cav1.1 provides a template for homology-based structural modeling of the evolutionarily related Nav channels. In this Resource article, we summarized all the reported disease-related mutations in human Nav channels, generated a homologous model of human Nav1.7, and structurally mapped disease-associated mutations. Before the determination of structures of human Nav channels, the analysis presented here serves as the base framework for mechanistic investigation of Nav channelopathies and for potential structure-based drug discovery.

  2. Structure-based assessment of disease-related mutations in human voltage-gated sodium channels.

    Science.gov (United States)

    Huang, Weiyun; Liu, Minhao; Yan, S Frank; Yan, Nieng

    2017-06-01

    Voltage-gated sodium (Na v ) channels are essential for the rapid upstroke of action potentials and the propagation of electrical signals in nerves and muscles. Defects of Na v channels are associated with a variety of channelopathies. More than 1000 disease-related mutations have been identified in Na v channels, with Na v 1.1 and Na v 1.5 each harboring more than 400 mutations. Na v channels represent major targets for a wide array of neurotoxins and drugs. Atomic structures of Na v channels are required to understand their function and disease mechanisms. The recently determined atomic structure of the rabbit voltage-gated calcium (Ca v ) channel Ca v 1.1 provides a template for homology-based structural modeling of the evolutionarily related Na v channels. In this Resource article, we summarized all the reported disease-related mutations in human Na v channels, generated a homologous model of human Na v 1.7, and structurally mapped disease-associated mutations. Before the determination of structures of human Na v channels, the analysis presented here serves as the base framework for mechanistic investigation of Na v channelopathies and for potential structure-based drug discovery.

  3. Trap Healing for High-Performance Low-Voltage Polymer Transistors and Solution-Based Analog Amplifiers on Foil.

    Science.gov (United States)

    Pecunia, Vincenzo; Nikolka, Mark; Sou, Antony; Nasrallah, Iyad; Amin, Atefeh Y; McCulloch, Iain; Sirringhaus, Henning

    2017-06-01

    Solution-processed semiconductors such as conjugated polymers have great potential in large-area electronics. While extremely appealing due to their low-temperature and high-throughput deposition methods, their integration in high-performance circuits has been difficult. An important remaining challenge is the achievement of low-voltage circuit operation. The present study focuses on state-of-the-art polymer thin-film transistors based on poly(indacenodithiophene-benzothiadiazole) and shows that the general paradigm for low-voltage operation via an enhanced gate-to-channel capacitive coupling is unable to deliver high-performance device behavior. The order-of-magnitude longitudinal-field reduction demanded by low-voltage operation plays a fundamental role, enabling bulk trapping and leading to compromised contact properties. A trap-reduction technique based on small molecule additives, however, is capable of overcoming this effect, allowing low-voltage high-mobility operation. This approach is readily applicable to low-voltage circuit integration, as this work exemplifies by demonstrating high-performance analog differential amplifiers operating at a battery-compatible power supply voltage of 5 V with power dissipation of 11 µW, and attaining a voltage gain above 60 dB at a power supply voltage below 8 V. These findings constitute an important milestone in realizing low-voltage polymer transistors for solution-based analog electronics that meets performance and power-dissipation requirements for a range of battery-powered smart-sensing applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Comparative Analysis of Voltage Control in Battery Power Converters for Inverter-Based AC Microgrids

    National Research Council Canada - National Science Library

    Chae, Woo-Kyu; Won, Jong-Nam; Lee, Hak-Ju; Kim, Jae-Eon; Kim, Jaehong

    2016-01-01

    .... The energy storage system power converters generally form the local AC bus voltage. This grid-forming operation requires fast and robust voltage control to properly maintain a stable energy flow and high power quality in the local AC bus...

  5. A Dynamic Consensus Algorithm based Low-Voltage Ride-Through Operation of Power Converters in Grid-Interactive Microgrids

    DEFF Research Database (Denmark)

    Zhao, Xin; Meng, Lexuan; Savaghebi, Mehdi

    2016-01-01

    The possibility of increasing penetration level of grid-interactive microgrids (MGs) has gained a great interest over the past decade. Thus, it is critical to investigate the performance of the MGs under voltage sags, since it may induce instability to the power grid. Negative sequence droop...... control based voltage support strategy has been proposed to aid MGs riding through three phase asymmetrical voltage sags. However, since the line impedance from each converter to the point of common coupling (PCC) is not identical, both positive sequence and negative sequence output current...

  6. A New High Frequency Injection Method Based on Duty Cycle Shifting without Maximum Voltage Magnitude Loss

    DEFF Research Database (Denmark)

    Wang, Dong; Lu, Kaiyuan; Rasmussen, Peter Omand

    2015-01-01

    The conventional high frequency signal injection method is to superimpose a high frequency voltage signal to the commanded stator voltage before space vector modulation. Therefore, the magnitude of the voltage used for machine torque production is limited. In this paper, a new high frequency...

  7. Research on installation quality inspection system of high voltage customer metering device based on image recognition

    Science.gov (United States)

    He, Bei; Yang, Fu-li; Tao, Xue-dan; Chang, Shi-liang; Wu, Kang

    2017-11-01

    With the rapid development of the scale of the power grid, the site construction and the operations environment is more widespread and more complex. The installation work of the high-voltage customer metering device is heavy, which is not standardized. In addition, managers supervise the site construction progress only through the person in charge of each work phrase. It is inefficient and difficult to control the multi-team and multi-unit cross work. Therefore, it is necessary to establish a scientific system to detect the quality of installation and management practices to standardize installation work of the metering device. Based on the research of image recognition and target detection system, this paper presents a high-voltage customer metering device installation quality inspection system based on digital image processing, image feature extraction and SVM classification decision. The experimental results show that the proposed scheme is feasible. And it can be used to accurately extract the metering components in the image, which can be also accurately and quickly classified. Our method is of great significance for the implementation and monitoring of the power system in installation and specification

  8. Energy consumption analysis of graphene based all spin logic device with voltage controlled magnetic anisotropy

    Directory of Open Access Journals (Sweden)

    Zhizhong Zhang

    2017-05-01

    Full Text Available All spin logic device (ASLD is a promising option to realize the ultra-low power computing systems. However, the low spin transport efficiency and the non-local switching of the detector have become two key challenges of the ASLD. In this paper, we analyze the energy consumption of a graphene based ASLD with the ferromagnetic layer switching assistance by voltage control magnetic anisotropy (VCMA effect. This structure has significant potential towards ultra-low power consumption: the applied voltage can not only shorten switching time of the ferromagnetic layer, but also decreases the critical injection current; the graphene channel enhances greatly the spin transport efficiency. By applying the approximate circuit model, the impact of material configurations, interfaces and geometry can be synthetically studied. An accurate physic model was also developed, based on which, we carry out the micro-magnetic simulations to analyze the magnetization dynamics. Combining these electrical and magnetic investigations, the energy consumption of the proposed ASLD can be estimated. With the optimizing parameters, the energy consumption can be reduced to 2.5 pJ for a logic operation.

  9. Voltage imaging in vivo with a new class of rhodopsin-based indicators

    Science.gov (United States)

    Douglass, Adam

    2013-03-01

    Reliable, optical detection of single action potentials in an intact brain is one of the longest-standing challenges in neuroscience. We have recently shown that a number of microbial rhodopsins exhibit intrinsic fluorescence that is sensitive to transmembrane potential. One class of indicator, derived from Archaerhodopsin-3 (Arch), responds to voltage transients with a speed and sensitivity that enable near-perfect identification of single action potentials in cultured neurons [Nat Methods. (2011). 9:90-5]. We have extended the use of these indicators to an in vivo context through the application of advanced imaging techniques to the larval zebrafish. Using planar-illumination, spinning-disk confocal, and epifluorescence imaging modalities, we have successfully recorded electrical activity in a variety of fish structures, including the brain and heart, in a completely noninvasive manner. Transgenic lines expressing Arch variants in defined cells enable comprehensive measurements to be made from specific target populations. In parallel, we have also extended the capabilities of our indicators by improving their multiphoton excitability and overall brightness. Microbial rhodopsin-based voltage indicators now enable optical interrogation of complex neural circuits, and electrophysiology in systems for which electrode-based techniques are challenging.

  10. Digital Control Techniques Based on Voltage Source Inverters in Renewable Energy Applications: A Review

    Directory of Open Access Journals (Sweden)

    Sohaib Tahir

    2018-02-01

    Full Text Available In the modern era, distributed generation is considered as an alternative source for power generation. Especially, need of the time is to provide the three-phase loads with smooth sinusoidal voltages having fixed frequency and amplitude. A common solution is the integration of power electronics converters in the systems for connecting distributed generation systems to the stand-alone loads. Thus, the presence of suitable control techniques, in the power electronic converters, for robust stability, abrupt response, optimal tracking ability and error eradication are inevitable. A comprehensive review based on design, analysis, validation of the most suitable digital control techniques and the options available for the researchers for improving the power quality is presented in this paper with their pros and cons. Comparisons based on the cost, schemes, performance, modulation techniques and coordinates system are also presented. Finally, the paper describes the performance evaluation of the control schemes on a voltage source inverter (VSI and proposes the different aspects to be considered for selecting a power electronics inverter topology, reference frames, filters, as well as control strategy.

  11. Stability Analysis of a Voltage-Based Controller for Robot Manipulators

    Directory of Open Access Journals (Sweden)

    Jorge Orrante-Sakanassi

    2013-01-01

    Full Text Available A voltage-based control scheme for robot manipulators has been presented in recent literature, where feedback linearization is applied in the electrical equations of the DC motors in order to cancel the electrical current terms. However, in this paper we show that this control technique generates a system of the form Ex = Ax + Bu, where E is a singular matrix, that is to say, a generalized state-space system or singular system. This paper introduces a formal stability analysis of the respective system by considering the state-space equation as a singular system. Furthermore, in order to avoid the singularity of the closed-loop system, modified voltage-based control schemes are proposed, whose Lyapunov stability analyses conclude semiglobal asymptotic stability for the set-point control case and uniform boundedness of the solutions and semiglobal convergence of the position, as well as velocity errors for the tracking control case. The proposed control systems are simulated for the tracking and set-point cases using the CICESE Pelican robot driven by DC motors.

  12. Physicotechnological aspects of low-voltage suppressors developement on the silicon base

    Directory of Open Access Journals (Sweden)

    Rakhmatov A. Z.

    2010-10-01

    Full Text Available It is shown that by arsenic diffusion alloying of silicon plates in conditions of deaerated quartz ampoule the most effective is the use of a compound source in the form of crystal arsenic and silicon powder of boron-implanted silicon grade with base impurity (boron concentration not less than the concentration of base impurity in alloyed silicon plates. The work defines experimental values of surface concentration, proper and effective diffusion coefficients that fit diffision conditions of As inside ampoule for 2 h at temperature 1423 K and pressure of As steams of 2·105 Pa. The received results are of interest in designing and producing of low-voltage (less than 7 V suppressors on the silicon base.

  13. GENDER-BASED RESTORATIVE JUSTICE FOR VICTIMS OF VIOELENCE AGAINST WOMEN

    Directory of Open Access Journals (Sweden)

    Cahya Wulandari

    2015-01-01

    Full Text Available Positive law is less oriented towards the protection of victims, especially women. Restorative justice appears to protect and resolve problems with the interests of the victim-oriented. This article discuss the form of legal protection for victims of violence against women, gender-based and describe the form of restorative justice for victims of gender-based violence against women. Positive criminal law does not accommodate both the interests of the victim to determine the crime against him self and to restore his suffering. This is caused due to the dominance of retributive justice in the settlement mind set crime through the criminal law. The restorative justice allows for an active role in the completion of a crime victim who happens also allows the imposition of sanctions that are beneficial to the recovery of the suffering of the victims.

  14. A Practice-Based Clinical Evaluation of a Bulk Fill Restorative Material.

    Science.gov (United States)

    Burke, F J Trevor; Crisp, Russell John; Panchal, Ditesh; Redfearn, Philip; Sands, Peter

    2016-09-01

    To evaluate the handling, by a group of practice-based researchers, of a recently introduced bulk fill resin-based composite restorative material, Filtek Bulk Fill Restorative (3M ESPE). The twelve selected evaluators were sent explanatory letters, a pack of the material under investigation to use for 8 weeks, and a questionnaire. The evaluators rated the ease of use of the bulk fill restorative the same as the previously used posterior composite material. The provision of one shade only for evaluation may have compromised the score for aesthetic quality. No post-operative sensitivity was reported. The bulk fill material was well received as indicated by the high number of evaluators who would both purchase the material and recommend it to colleagues. A recently introduced bulk fill restorative material achieved a rating for handling which was similar to the evaluators' previously used resin composite, although there were some concerns regarding the translucency of the material.

  15. An Enhanced LVRT Scheme for DFIG-based WECSs under Both Balanced and Unbalanced Grid Voltage Sags

    DEFF Research Database (Denmark)

    Mohammadi, Jafar; Afsharnia, Saeed; Ebrahimzadeh, Esmaeil

    2017-01-01

    Due to the latest grid codes, wind energy conversion systems (WECSs) are required to remain connected to grid under grid voltage sags and supply reactive power into the grid. So, this paper proposes an enhanced scheme to improve low-voltage ride through (LVRT) capability of doubly fed induction...... generator (DFIG)-based WECSs under both balanced and unbalanced grid voltage sags. The proposed scheme is composed of active and passive LVRT compensators. The active compensator is performed by controlling the rotor- and grid-side converters of the DFIG to decrease the stator flux oscillations and inject...... reactive power into the grid. The passive compensator is based on a three-phase stator damping resistor (SDR) located in series with the stator windings. The proposed scheme decreases the negative effects of grid voltage sags in the DFIG system including the rotor over-currents, electromagnetic torque...

  16. Survival of extensive restorations in primary molars: 15-year practice-based study.

    Science.gov (United States)

    Tseveenjav, Battsetseg; Furuholm, Jussi; Mulic, Aida; Valen, Håkon; Maisala, Tuomo; Turunen, Seppo; Varsio, Sinikka; Auero, Merja; Tjäderhane, Leo

    2017-12-03

    Caries decline in the western world is accompanied by strong polarization among children; 8% of Finnish 5-year-olds having 76% of untreated caries. This high caries risk group needs preventive and restorative strategies. To explore survival of extensive restorations in primary molars. This study was based on health records from 2002 to 2016 of children under 18 years. Of severely affected primary molars (n = 1061), 41% were restored with preformed metal crowns (PMCs), 38% with glass-ionomer cement (GIC)/polyacid-modified resin composite (PAMRC)/resin-modified GIC (RMGIC), and 21% with resin composites (RC). Younger children (3-8) received 97% of the PMCs and 86% of GIC/PAMRC/RMGIC; older ones (≥9) 91% of the RC restorations. Neither amalgam nor indirect restorations were registered. General dentists (GDs) engaged in primary care restored with GIC/PAMRC/RMGIC (52%) or RC (48%). GDs in general anesthesia care service placed 66% and specializing/specialized dentists 31% of PMCs. PMCs had lower failure rate (1.4% vs 3.0%) than GIC/PAMRC/RMGIC (P = 0.001). Choosing PMCs reduced patient visits compared to other restorations (P < 0.001). Severely affected primary molars of children at high caries risk are better managed, using PMCs to optimize the resources in public oral health services. © 2017 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  17. Evidence-based Update of Pediatric Dental Restorative Procedures: Preventive Strategies.

    Science.gov (United States)

    Tinanoff, N; Coll, J A; Dhar, V; Maas, W R; Chhibber, S; Zokaei, L

    2015-01-01

    There has been significant advances in the understanding of preventive restorative procedures regarding the advantages and disadvantages for restorative procedures; the evidence for conservative techniques for deep carious lesions; the effectiveness of pit and fissure sealants; and the evidence for use of resin infiltration techniques. The intent of this review is to help practitioners use evidence to make decisions regarding preventive restorative dentistry in children and young adolescents. This evidence-based review appraises the literature, primarily between the years 1995-2013, on preventive restorative strategies. The evidence was graded as to strong evidence, evidence in favor, or expert opinion by consensus of authors Results: The preventive strategy for dental caries includes individualized assessment of disease progression and management with appropriate preventive and restorative therapy. There is strong evidence that restoration of teeth with incomplete caries excavation results in fewer signs and symptoms of pulpal disease than complete excavation. There is strong evidence that sealants should be placed on pit and fissure surfaces judged to be at risk for dental caries, and surfaces that already exhibit incipient, non-cavitated carious lesions. There is evidence in favor for resin infiltration to improve the clinical appearance of white spot lesions. Substantial evidence exists in the literature regarding the value of preventive dental restorative procedures.

  18. A Novel High-Frequency Voltage Standing-Wave Ratio-Based Grounding Electrode Line Fault Supervision in Ultra-High Voltage DC Transmission Systems

    Directory of Open Access Journals (Sweden)

    Yufei Teng

    2017-03-01

    Full Text Available In order to improve the fault monitoring performance of grounding electrode lines in ultra-high voltage DC (UHVDC transmission systems, a novel fault monitoring approach based on the high-frequency voltage standing-wave ratio (VSWR is proposed in this paper. The VSWR is defined considering a lossless transmission line, and the characteristics of the VSWR under different conditions are analyzed. It is shown that the VSWR equals 1 when the terminal resistance completely matches the characteristic impedance of the line, and when a short circuit fault occurs on the grounding electrode line, the VSWR will be greater than 1. The VSWR will approach positive infinity under metallic earth fault conditions, whereas the VSWR in non-metallic earth faults will be smaller. Based on these analytical results, a fault supervision criterion is formulated. The effectiveness of the proposed VSWR-based fault supervision technique is verified with a typical UHVDC project established in Power Systems Computer Aided Design/Electromagnetic Transients including DC(PSCAD/EMTDC. Simulation results indicate that the proposed strategy can reliably identify the grounding electrode line fault and has strong anti-fault resistance capability.

  19. The Design and Characterization of a Prototype Wideband Voltage Sensor Based on a Resistive Divider.

    Science.gov (United States)

    Garnacho, Fernando; Khamlichi, Abderrahim; Rovira, Jorge

    2017-11-17

    The most important advantage of voltage dividers over traditional voltage transformers is that voltage dividers do not have an iron core with non-linear hysteresis characteristics. The voltage dividers have a linear behavior with respect to over-voltages and a flat frequency response larger frequency range. The weak point of a voltage divider is the influence of external high-voltage (HV) and earth parts in its vicinity. Electrical fields arising from high voltages in neighboring phases and from ground conductors and structures are one of their main sources for systematic measurement errors. This paper describes a shielding voltage divider for a 24 kV medium voltage network insulated in SF6 composed of two resistive-capacitive dividers, one integrated within the other, achieving a flat frequency response up to 10 kHz for ratio error and up to 5 kHz for phase displacement error. The metal shielding improves its immunity against electric and magnetic fields. The characterization performed on the built-in voltage sensor shows an accuracy class of 0.2 for a frequency range from 20 Hz to 5 kHz and a class of 0.5 for 1 Hz up to 20 Hz. A low temperature effect is also achieved for operation conditions of MV power grids.

  20. The Design and Characterization of a Prototype Wideband Voltage Sensor Based on a Resistive Divider

    Directory of Open Access Journals (Sweden)

    Fernando Garnacho

    2017-11-01

    Full Text Available The most important advantage of voltage dividers over traditional voltage transformers is that voltage dividers do not have an iron core with non-linear hysteresis characteristics. The voltage dividers have a linear behavior with respect to over-voltages and a flat frequency response larger frequency range. The weak point of a voltage divider is the influence of external high-voltage (HV and earth parts in its vicinity. Electrical fields arising from high voltages in neighboring phases and from ground conductors and structures are one of their main sources for systematic measurement errors. This paper describes a shielding voltage divider for a 24 kV medium voltage network insulated in SF6 composed of two resistive-capacitive dividers, one integrated within the other, achieving a flat frequency response up to 10 kHz for ratio error and up to 5 kHz for phase displacement error. The metal shielding improves its immunity against electric and magnetic fields. The characterization performed on the built-in voltage sensor shows an accuracy class of 0.2 for a frequency range from 20 Hz to 5 kHz and a class of 0.5 for 1 Hz up to 20 Hz. A low temperature effect is also achieved for operation conditions of MV power grids.

  1. Evidence-based Update of Pediatric Dental Restorative Procedures: Dental Materials.

    Science.gov (United States)

    Dhar, V; Hsu, K L; Coll, J A; Ginsberg, E; Ball, B M; Chhibber, S; Johnson, M; Kim, M; Modaresi, N; Tinanoff, N

    2015-01-01

    The science of dental materials and restorative care in children and adolescent is constantly evolving, and the ongoing search for ideal restorative materials has led to plethora of research. To provide an evidence base to assist dental practitioners choose appropriate restorative care for children and adolescents. This evidence-based review appraises this literature, primarily between the years 1995-2013, for efficacy of dental amalgam, composites, glass ionomer cements, compomers, preformed metal crowns and anterior esthetic restorations. The assessment of evidence for each dental material was based on a strong evidence, evidence in favor, expert opinion, and evidence against by consensus of the authors. There is varying level of evidence for the use of restorative materials like amalgam, composites, glass ionomers, resin-modified glass-ionomers, compomers, stainless steel crowns and anterior crowns for both primary and permanent teeth. A substantial amount data is available on restorative materials used in pediatric dentistry; however, there exists substantial evidence from systematic reviews and randomized clinical trials and clinicians need to examine and understand the available literature evidence carefully to aid them in clinical decision making.

  2. Analog-to-digital conversion for low-frequency waveforms based on the Josephson voltage standard

    Science.gov (United States)

    Kim, Mun-Seog; Kim, Kyu-Tae; Kim, Wan-Seop; Chong, Yonuk; Kwon, Sung-Won

    2010-11-01

    A waveform synthesizer adopting a superconductor-normal metal-superconductor junction array has been developed, which can generate arbitrary stepwise waveforms with a number of quantum-voltage steps up to 1 V level amplitude. As an application of the synthesizer, we have built a sampling voltmeter that measures the differential voltages between a sinusoidal waveform produced by a semiconductor-based ac source and the Josephson waveforms. We carried out extensive sampling measurements for a 50 Hz sine wave with 1 V amplitude, applying sampling apertures in the range of 55 µs <=ta <= 130 µs and using Josephson waveforms with 32, 60, 80 and 100 quantum steps. From the measurements, the amplitude of the ac waveform was determined with a type A uncertainty (k = 2) of 0.15 µV. Also, we elucidated how the phase jitter in the ac waveform is reflected in the overall uncertainty for the measurements. The type B uncertainty due to the jitter is at least one order of magnitude smaller than the type A uncertainty.

  3. Passivity-based design of robust passive damping for LCL-filtered voltage source converters

    DEFF Research Database (Denmark)

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

    2015-01-01

    Passive damping is proven as a robust stabilizing technique for LCL-filtered voltage source converters. However, conventional design methods of passive dampers are based on the passive components only, while the inherent damping effect of time delay in the digital control system is overlooked....... In this paper, a frequency-domain passivity-based design approach is proposed, where the passive dampers are designed to eliminate the negative real part of the converter output admittance with closed-loop current control, rather than shaping the LCL-filter itself. Thus, the influence of time delay...... in the current control is included, which allows a relaxed design of the passive damper with the reduced power loss and improved stability robustness against grid parameters variations. Design procedures of two commonly used passive dampers with LCL-filtered VSCs are illustrated. Experimental results validate...

  4. Converter-flux-based current control of voltage source PWM rectifiers - analysis and implementation

    Energy Technology Data Exchange (ETDEWEB)

    Poellaenen, R.

    2003-07-01

    Pulsewidth-modulated (PWM) rectifier technology is increasingly used in industrial applications like variable-speed motor drives, since it offers several desired features such as sinusoidal input currents, controllable power factor, bidirectional power flow and high quality DC output voltage. To achieve these features, however, an effective control system with fast and accurate current and DC voltage responses is required. From various control strategies proposed to meet these control objectives, in most cases the commonly known principle of the synchronous-frame current vector control along with some space-vector PWM scheme have been applied. Recently, however, new control approaches analogous to the well-established direct torque control (DTC) method for electrical machines have also emerged to implement a high-performance PWM rectifier. In this thesis the concepts of classical synchronous-frame current control and DTC-based PWM rectifier control are combined and a new converter-flux-based current control (CFCC) scheme is introduced. To achieve sufficient dynamic performance and to ensure a stable operation, the proposed control system is thoroughly analysed and simple rules for the controller design are suggested. Special attention is paid to the estimation of the converter flux, which is the key element of converter-flux-based control. Discrete-time implementation is also discussed. Line-voltage-sensorless reactive reactive power control methods for the L- and LCL-type line filters are presented. For the L-filter an open-loop control law for the d-axis current reference is proposed. In the case of the LCL-filter the combined open-loop control and feedback control is proposed. The influence of the erroneous filter parameter estimates on the accuracy of the developed control schemes is also discussed. A new zero vector selection rule for suppressing the zero-sequence current in parallel-connected PWM rectifiers is proposed. With this method a truly standalone and

  5. Longevity of direct restorations in Dutch dental practices. Descriptive study out of a practice based research network.

    NARCIS (Netherlands)

    Laske, M.; Opdam, N.J.M.; Bronkhorst, E.M.; Braspenning, J.C.C.; Huysmans, M.C.D.N.J.M.

    2016-01-01

    OBJECTIVES: The aim of this retrospective practice-based study was to investigate the longevity of direct restorations placed by a group of general dental practitioners (GDPs) and to explore the effect of practice/operator, patient, and tooth/restoration related factors on restoration survival.

  6. Voltage-Balancing Method for Modular Multilevel Converters Under Phase-Shifted Carrier-Based Pulsewidth Modulation

    DEFF Research Database (Denmark)

    Deng, Fujin; Chen, Zhe

    2015-01-01

    The modular multilevel converter (MMC) becomes attractive for medium- or high-power applications because of the advantages of high modularity, availability, and power quality. One of the technical challenges associated with an MMC is the balancing of the capacitors' voltages. In this paper......, a voltage-balancing control method is proposed for the MMC under phase-shifted carrier-based pulsewidth modulation. The proposed voltage-balancing method uses the linearization method for pulse sorting without arm current measurement, which can control the capacitor charge transfer to balance the capacitor...... voltage in the MMC. In the proposed method, the voltagebalancing algorithm is implemented in each carrier wave period, which reduces the computational intensity and burden. In addition, the arm current can also be improved with the proposed method. The simulation studies with the professional tool PSCAD...

  7. Instability of Wind Turbine Converters during Current Injection to Low Voltage Grid Faults and PLL Frequency Based Stability Solution

    DEFF Research Database (Denmark)

    Göksu, Ömer; Teodorescu, Remus; Bak, Claus Leth

    2014-01-01

    turbines lose synchronism with the grid fundamental frequency (e.g., 50 Hz) during very deep voltage sags, is explored with its theory, analyzed and a novel stability solution based on PLL frequency is proposed; and both are verified with power system simulations and by experiments on a grid......In recent grid codes for wind power integration, wind turbines are required to stay connected during grid faults even when the grid voltage drops down to zero; and also to inject reactive current in proportion to the voltage drop. However, a physical fact, instability of grid-connected converters...... during current injection to very low (close to zero) voltage faults, has been omitted, i.e., failed to be noticed in the previous wind power studies and grid code revisions. In this paper, the instability of grid side converters of wind turbines defined as loss of synchronism (LOS), where the wind...

  8. Negative Sequence Droop Method based Hierarchical Control for Low Voltage Ride-Through in Grid-Interactive Microgrids

    DEFF Research Database (Denmark)

    Zhao, Xin; Firoozabadi, Mehdi Savaghebi; Quintero, Juan Carlos Vasquez

    2015-01-01

    In highly microgrid (MG) integrated distribution systems, problems such as a sudden cut out of the MGs due to grid faults may lead to adverse effects to the grid. As a consequence, ancillary services provided by MGs are preferred since it can make the MG a contributor to ride through the faults....... In this paper, a voltage support strategy based on negative sequence droop control, which regulate the positive/negative sequence active and reactive power flow by means of sending proper voltage reference to the inner control loop, is proposed for the grid connected MGs to ride through voltage sags under...... complex line impedance conditions. In this case, the MGs should inject a certain amount of positive and negative sequence power to the grid so that the voltage quality at load side can be maintained at a satisfied level. A two layer hierarchical control strategy is proposed in this paper. The primary...

  9. A high voltage pulse generator based on silicon-controlled rectifier for field-reversed configuration experiment

    Science.gov (United States)

    Lin, Munan; Liu, Ming; Zhu, Guanghui; Wang, Yanpeng; Shi, Peiyun; Sun, Xuan

    2017-08-01

    A high voltage pulse generator based on a silicon-controlled rectifier has been designed and implemented for a field reversed configuration experiment. A critical damping circuit is used in the generator to produce the desired pulse waveform. Depending on the load, the rise time of the output trigger signal can be less than 1 μs, and the peak amplitudes of trigger voltage and current are up to 8 kV and 85 A in a single output. The output voltage can be easily adjusted by changing the voltage on a capacitor of the generator. In addition, the generator integrates an electrically floating heater circuit so it is capable of triggering either pseudosparks (TDI-type hydrogen thyratron) or ignitrons. Details of the circuits and their implementation are described in the paper. The trigger generator has successfully controlled the discharging sequence of the pulsed power supply for a field reversed configuration experiment.

  10. High breakdown voltage GaN-on-insulator based heterojunction field effect transistor with a partial back barrier layer

    Science.gov (United States)

    Du, Jiangfeng; Li, Ruonan; Bai, Zhiyuan; Liu, Yong; Yu, Qi

    2017-11-01

    A high breakdown voltage GaN-on-Insulator based heterojunction field effect transistor with a partial back barrier (PB-GOI HFET) is proposed in this paper. The partial back barrier (PB) formed by AlGaN is located in the GaN channel layer, which can make the breakdown voltage improved significantly by modulating the distribution of electric field along the channel. PB-GOI HFET can not only maintain the original advantages of GOI structure, but also improve the breakdown voltage without degradation of frequency performance. Compared with a conventional GOI HFET, the proposed PB-GOI HFET with gate-drain distance of 5 μm possesses the breakdown voltage of 1200 V and the FOM of 3.12 GW/cm2, which increased by more than 353% and 976%. The novel PB-GOI HFET shows great prospects in power electronics applications.

  11. Science Base and Tools for Evaluating Stream Restoration Project Proposals.

    Science.gov (United States)

    Cluer, B.; Thorne, C.; Skidmore, P.; Castro, J.; Pess, G.; Beechie, T.; Shea, C.

    2008-12-01

    Stream restoration, stabilization, or enhancement projects typically employ site-specific designs and site- scale habitat improvement projects have become the default solution to many habitat problems and constraints. Such projects are often planned and implemented without thorough consideration of the broader scale problems that may be contributing to habitat degradation, attention to project resiliency to flood events, accounting for possible changes in climate or watershed land use, or ensuring the long term sustainability of the project. To address these issues, NOAA Fisheries and USFWS have collaboratively commissioned research to develop a science document and accompanying tools to support more consistent and comprehensive review of stream management and restoration projects proposals by Service staff responsible for permitting. The science document synthesizes the body of knowledge in fluvial geomorphology and presents it in a way that is accessible to the Services staff biologists, who are not trained experts in this field. Accompanying the science document are two electronic tools: a Project Information Checklist to assist in evaluating whether a proposal includes all the information necessary to allow critical and thorough project evaluation; and a Project Evaluation Tool (in flow chart format) that guides reviewers through the steps necessary to critically evaluate the quality of the information submitted, the goals and objectives of the project, project planning and development, project design, geomorphic-habitat-species relevance, and risks to listed species. Materials for training Services staff and others in the efficient use of the science document and tools have also been developed. The longer term goals of this effort include: enabling consistent and comprehensive reviews that are completed in a timely fashion by regulators; facilitating improved project planning and design by proponents; encouraging projects that are attuned to their watershed

  12. Approach to fitting parameters and clustering for characterising measured voltage dips based on two-dimensional polarisation ellipses

    Energy Technology Data Exchange (ETDEWEB)

    García-Sánchez, Tania; Gómez-Lázaro, Emilio; Muljadi, E.; Kessler, Mathieu; Molina-García, Angel

    2017-08-16

    An alternative approach to characterise real voltage dips is proposed and evaluated in this study. The proposed methodology is based on voltage-space vector solutions, identifying parameters for ellipses trajectories by using the least-squares algorithm applied on a sliding window along the disturbance. The most likely patterns are then estimated through a clustering process based on the k-means algorithm. The objective is to offer an efficient and easily implemented alternative to characterise faults and visualise the most likely instantaneous phase-voltage evolution during events through their corresponding voltage-space vector trajectories. This novel solution minimises the data to be stored but maintains extensive information about the dips including starting and ending transients. The proposed methodology has been applied satisfactorily to real voltage dips obtained from intensive field-measurement campaigns carried out in a Spanish wind power plant up to a time period of several years. A comparison to traditional minimum root mean square-voltage and time-duration classifications is also included in this study.

  13. Voltage sensitivity based reactive power control on VSC-HVDC in a wind farm connected hybrid multi-infeed HVDC system

    DEFF Research Database (Denmark)

    Liu, Yan; Chen, Zhe

    2013-01-01

    With increasing application of both Line Commutated Converter based High Voltage Direct Current (LCC-HVDC) systems and Voltage Source Converter based HVDC (VSC-HVDC) links, a new type of system structure named Hybrid Multi-Infeed HVDC (HMIDC) system is formed in the modern power systems. This paper...... presents the operation and control method of the wind farm connected HMIDC system. The wind power fluctuation takes large influence to the system voltages. In order to reduce the voltage fluctuation of LCC-HVDC infeed bus caused by the wind power variation, a voltage sensitivity-based reactive power...

  14. Shunt hybrid active power filter under nonideal voltage based on fuzzy logic controller

    Science.gov (United States)

    Dey, Papan; Mekhilef, Saad

    2016-09-01

    In this paper, a synchronous reference frame (SRF) method based on a modified phase lock loop (PLL) circuit is developed for a three-phase four-wire shunt hybrid active power filter (APF). Its performance is analysed under unbalanced grid conditions. The dominant lower order harmonics as well as reactive power can be compensated by the passive elements, whereas the active part mitigates the remaining distortions and improves the power quality. As different control methods show contradictory performance, fuzzy logic controller is considered here for DC-link voltage regulation of the inverter. Extensive simulations of the proposed technique are carried out in a MATLAB-SIMULINK environment. A laboratory prototype has been built on dSPACE1104 platform to verify the feasibility of the suggested SHAPF controller. The simulation and experimental results validate the effectiveness of the proposed technique.

  15. Current-Voltage Characteristics of the Composites Based on Epoxy Resin and Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Iwona Pełech

    2015-01-01

    Full Text Available Polymer composites based on epoxy resin were prepared. Multiwalled carbon nanotubes synthesized on iron-cobalt catalyst were applied as a filler in a polymer matrix. Chlorine or hydroxyl groups were incorporated on the carbon nanotubes surface via chlorination or chlorination followed by hydroxylation. The effect of functionalized carbon nanotubes on the epoxy resin matrix is discussed in terms of the state of CNTs dispersion in composites as well as electrical properties. For the obtained materials current-voltage characteristics were determined. They had a nonlinear character and were well described by an exponential-type equation. For all the obtained materials the percolation threshold occurred at a concentration of about 1 wt%. At a higher filler concentration >2 wt%, better conductivity was demonstrated by polymer composites with raw carbon nanotubes. At a lower filler concentration <2 wt%, higher values of electrical conductivity were obtained for polymer composites with modified carbon nanotubes.

  16. MOSFET-based high voltage double square-wave pulse generator with an inductive adder configuration

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xin [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an 710049 (China); Zhang, Qiaogen, E-mail: hvzhang@mail.xjtu.edu.cn [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an 710049 (China); Long, Jinghua [College of Physics, Shenzhen University, Shenzhen 518060 (China); Lei, Yunfei; Liu, Jinyuan [Institute of Optoelectronics, Shenzhen University, Shenzhen 518060 (China)

    2015-09-01

    This paper presents a fast MOSFET-based solid-state pulse generator for high voltage double square-wave pulses. The generator consists mainly of an inductive adder system stacked of 20 solid-state modules. Each of the modules has 18 power MOSFETs in parallel, which are triggered by individual drive circuits; these drive circuits themselves are synchronously triggered by a signal from avalanche transistors. Our experiments demonstrate that the output pulses with amplitude of 8.1 kV and peak current of about 405 A are available at a load impedance of 20 Ω. The pulse has a double square-wave form with a rise and fall time of 40 ns and 26 ns, respectively and bottom flatness better than 12%. The interval time of the double square-wave pulses can be adjustable by varying the interval time of the trigger pulses.

  17. A 70 kV solid-state high voltage pulse generator based on saturable pulse transformer.

    Science.gov (United States)

    Fan, Xuliang; Liu, Jinliang

    2014-02-01

    High voltage pulse generators are widely applied in many fields. In recent years, solid-state and operating at repetitive mode are the most important developing trends of high voltage pulse generators. A solid-state high voltage pulse generator based on saturable pulse transformer is proposed in this paper. The proposed generator is consisted of three parts. They are charging system, triggering system, and the major loop. Saturable pulse transformer is the key component of the whole generator, which acts as a step-up transformer and main switch during working process of this generator. The circuit and working principles of the proposed pulse generator are introduced first in this paper, and the saturable pulse transformer used in this generator is introduced in detail. Circuit of the major loop is simulated to verify the design of the system. Demonstration experiments are carried out, and the results show that when the primary energy storage capacitor is charged to a high voltage, such as 2.5 kV, a voltage with amplitude of 86 kV can be achieved on the secondary winding. The magnetic core of saturable pulse transformer is saturated deeply and the saturable inductance of the secondary windings is very small. The switch function of the saturable pulse transformer can be realized ideally. Therefore, a 71 kV output voltage pulse is formed on the load. Moreover, the magnetic core of the saturable pulse transformer can be reset automatically.

  18. Designing a Battery-Less Piezoelectric based Energy Harvesting Interface Circuit with 300 mV Startup Voltage

    Science.gov (United States)

    Sarker, M. R.; Ali, Sawal H. Md; Othman, M.; Islam, Shabiul

    2013-04-01

    This paper presents a designing a battery-less piezoelectric based energy harvesting interface circuits with 300mV step-up voltage. A technique (i.e., DC-DC Step-Up converter) has chosen for designing the startup voltage with low voltage energy (i.e., 300mV). The proposed method consumes very little power, and is especially suitable for the ambient environmental source, where energy harvested power is very low. The energy harvesting interface circuit consists of MOSFET bridge ac-dc rectifier, voltage regulator, dc-dc step-up converter and an energy storage device with capacitor at the output terminal, replacing this by external battery. This paper will study results these important issues regarding the efficiencies of the energy harvesting power conversion interface circuits considering the storage device low voltage. The achievement of our development circuit is able to boost up minimum 1.67 V for input DC voltage of 300mV. The overall circuit efficiency is greater than 80% following the simulation results. This research has focused on the application of Wireless Sensor Network (WSN) and bio-medical device can be operated without battery.

  19. Line-to-line voltage based modulation scheme for single-phase reduced switch ac-dc-ac converters to achieve improved performance

    DEFF Research Database (Denmark)

    Qin, Zian; Loh, Poh Chiang; Blaabjerg, Frede

    2015-01-01

    . With the SVPWM or DPWM proposed in literatures, the generation of the references is phase voltage based. But the phase voltages actually cannot be controlled directly by the PWM converter, since they can be influenced by both of terminal voltages and the load network while the PWM converter can only control...... the former. It thus introduces complexity to the generation of the references, especially in unbalanced source or load condition. In this paper, a line-to-line voltage based PWM reference generation method is proposed. The proposed method is easy to be implemented to maximize the DC link voltage utilization...

  20. Reducing composite restoration polymerization shrinkage stress through resin modified glass-ionomer based adhesives.

    Science.gov (United States)

    Naoum, S J; Mutzelburg, P R; Shumack, T G; Thode, Djg; Martin, F E; Ellakwa, A E

    2015-12-01

    The aim of this study was to determine whether employing resin modified glass-ionomer based adhesives can reduce polymerization contraction stress generated at the interface of restorative composite adhesive systems. Five resin based adhesives (G Bond, Optibond-All-in-One, Optibond-Solo, Optibond-XTR and Scotchbond-Universal) and two resin modified glass-ionomer based adhesives (Riva Bond-LC, Fuji Bond-LC) were analysed. Each adhesive was applied to bond restorative composite Filtek-Z250 to opposing acrylic rods secured within a universal testing machine. Stress developed at the interface of each adhesive-restorative composite system (n = 5) was calculated at 5-minute intervals over 6 hours. The resin based adhesive-restorative composite systems (RBA-RCS) demonstrated similar interface stress profiles over 6 hours; initial rapid contraction stress development (0-300 seconds) followed by continued contraction stress development ≤0.02MPa/s (300 seconds - 6 hours). The interface stress profile of the resin modified glass-ionomer based adhesive-restorative composite systems (RMGIBA-RCS) differed substantially to the RBA-RCS in several ways. Firstly, during 0-300 seconds the rate of contraction stress development at the interface of the RMGIBA-RCS was significantly (p glass-ionomer based adhesives can significantly reduce the magnitude and rate of polymerization contraction stress developed at the interface of adhesive-restorative composite systems. © 2015 Australian Dental Association.

  1. Design of High-Voltage Switch-Mode Power Amplifier Based on Digital-Controlled Hybrid Multilevel Converter

    Directory of Open Access Journals (Sweden)

    Yanbin Hou

    2016-01-01

    Full Text Available Compared with conventional Class-A, Class-B, and Class-AB amplifiers, Class-D amplifier, also known as switching amplifier, employs pulse width modulation (PWM technology and solid-state switching devices, capable of achieving much higher efficiency. However, PWM-based switching amplifier is usually designed for low-voltage application, offering a maximum output voltage of several hundred Volts. Therefore, a step-up transformer is indispensably adopted in PWM-based Class-D amplifier to produce high-voltage output. In this paper, a switching amplifier without step-up transformer is developed based on digital pulse step modulation (PSM and hybrid multilevel converter. Under the control of input signal, cascaded power converters with separate DC sources operate in PSM switch mode to directly generate high-voltage and high-power output. The relevant topological structure, operating principle, and design scheme are introduced. Finally, a prototype system is built, which can provide power up to 1400 Watts and peak voltage up to ±1700 Volts. And the performance, including efficiency, linearity, and distortion, is evaluated by experimental tests.

  2. Parameters Designing of Slide Mode Variable Structure Controller of Bus Voltage of DC Microgrid Based on Proportion Switching Function

    Directory of Open Access Journals (Sweden)

    Sun Zhenchuan

    2017-01-01

    Full Text Available Constant value control of the DC-bus voltage is a essential problem of the control system of the DC microgrids. DC-DC converters are applied in parallel to realize the transform of energy from the distributed generations (DGs to the DC-bus. Droop control methods are applied to the DC-bus voltage while PI controllers are used in controlling the duty ratios of the converters. This method may bring out the slow response speed of the system accompanied by the large ripple of the voltage. The slide mode variable structure control can speed up the response and reduce the ripple of the voltage as well. In the traditional slide mode control based on the proportion switching function, the denominator of the transfer function of the controlled plant is a second-order characteristic polynomial without the constant term. The denominators of the transfer functions of the buck DC-DC converters contain the constant terms. The designing of the parameters of the slide mode control based on the proportion switching function is analyzed based on mathematics deductions. Simulation results show that the selected parameters can not only speed up the response of the system but also greatly reduce the ripple of the voltage.

  3. Passivity-Based Control by Series/Parallel Damping of Single-Phase PWM Voltage Source Converter

    NARCIS (Netherlands)

    del Puerto Flores, Dunstano; Scherpen, Jacqueline; Liserre, Marco; de Vries, Martijn M. J.; Kransse, Marco J.; Monopoli, Vito Giuseppe

    This paper describes a detailed design procedure for passivity-based controllers developed using the Brayton-Moser (BM) framework. Several passivity-based feedback designs are presented for the voltage-source converter, specifically for the H-bridge converter, since nowadays it is one of the

  4. Antibacterial resin monomers based on quaternary ammonium and their benefits in restorative dentistry

    Directory of Open Access Journals (Sweden)

    Satoshi Imazato

    2012-08-01

    Full Text Available Antibacterial resin monomers are unique molecules that provide dental resins with “bio-active function”, i.e. the ability to control bacterial infection. They have strong antibacterial activity when unpolymerized and also demonstrate contact inhibitory effects after being polymerized without releasing antibacterial components. Intensive research has been conducted on antibacterial monomers based on quaternary ammonium, such as methacryloyloxydodecylpyridinium bromide (MDPB, focusing on their basic properties and uses in several resinous restoratives. As represented by successful commercialization of an adhesive system incorporating MDPB, quaternary ammonium based antibacterial monomers have the potential for utilization in various restorative materials and regimens, including caries management and pulp care.

  5. Voltage-Controlled Magnetic Anisotropy in Heavy Metal/Ferromagnet/Insulator-Based Structures

    Science.gov (United States)

    Li, Xiang

    Electric-field assisted writing of magnetic memory that exploits the voltage-controlled magnetic anisotropy (VCMA) effect offers a great potential for high density and low power applications. Magnetoelectric Random Access Memory (MeRAM) has been investigated due to its lower switching current, compared with traditional current-controlled devices utilizing spin transfer torque (STT) or spin-orbit torque (SOT) for magnetization switching. It is of great promise to integrate MeRAM into the advanced CMOS back-end-of-line (BEOL) processes for on-chip embedded applications, and enable non-volatile electronic systems with low static power dissipation and instant-on operation capability. In this thesis, different heavy metal|ferromagnet|insulator-based structures are grown by magnetron sputtering to improve the VCMA effect over the traditional Ta|CoFeB|MgO-based structures. We also established an accurate measurement technique for VCMA characterization. An improved thermal annealing stability of VCMA over 400°C is achieved in Mo|CoFeB|MgO-based structures. In addition, we observed a weak CoFeB thickness dependence of both VCMA coefficient and interfacial perpendicular magnetic anisotropy (PMA) in both Ta|CoFeB|MgO and Mo|CoFeB|MgO-based structures.

  6. Restorative Treatment Thresholds for Interproximal Primary Caries Based on Radiographic Images: Findings from The Dental PBRN

    Science.gov (United States)

    Gordan, Valeria V; Garvan, Cynthia W; Heft, Marc W.; Fellows, Jeffrey L; Qvist, Vibeke; Rindal, D. Brad; Gilbert, Gregg H

    2010-01-01

    Objectives To: (1) quantify at which proximal caries lesion depths dentists in regular clinical practice intervene restoratively, based on hypothetical scenarios that present radiographic images and patient background information, and (2) identify characteristics that are associated with restorative intervention in lesions that have penetrated only the enamel surface. Methods Dentists in a practice-based research network (www.DentalPBRN.org) who reported doing at least some restorative dentistry were surveyed (n=901). Dentists were asked to indicate at which lesion depth they would intervene restoratively based on a series of radiographic images depicting interproximal caries at increasing lesion depths in a mandibular premolar tooth. Dentists were also questioned regarding two caries risk scenarios: one patient with low caries risk and another at higher risk. We used logistic regression to analyze associations between the decision to intervene restoratively and specific dentist, practice, and patient characteristics. Results Five hundred (56%) DPBRN practitioner-investigators completed the survey. In a high caries risk patient, 66% of dentists indicated that they would restore a proximal enamel lesion, and 24% would once the lesion had reached into the outer one-third of the dentin. In a low caries risk patient, 39% of dentists reported that they would restore an enamel lesion, and 54% would once the lesion had reached into the outer one-third of the dentin. In multivariate analyses, when accounting for dentist and practice characteristics, dentists in large group practices were less likely to intervene surgically for enamel caries regardless of patient's caries risk. Conclusions Restorative treatment thresholds based on radiographic lesion depth varied substantially among dentists. Most dentists would restore lesions that were still within the enamel surface for high caries risk individuals. Dentists’ decisions to intervene surgically in the caries process

  7. a microprocessor-based control, scheme for a pwm voltage-fed

    African Journals Online (AJOL)

    Dr Obe

    other hand, the PWM voltage source inverter. (VSI) with force or self-commutated thyristor and /or transistors does not suffer from any of the above limitations. In addition, the ability of the PWM force /self –commutated VSI to supply the induction heating load at unity power factor minimizes circuit current and voltage stresses ...

  8. Coordinated control for low voltage ride-through of a PMSG-based wind power plant

    Directory of Open Access Journals (Sweden)

    Khagendra Thapa

    2016-01-01

    Full Text Available Wind turbine generators should be kept connected to a power grid, while supporting the voltage recovery in the case of a grid fault to meet low voltage ride-through requirement in some grid codes. This paper proposes a coordinated control scheme that prevents the increase in the DC-link voltage by reducing the active power in the machine side converter of permanent magnet synchronous generators (PMSGs in proportion to the voltage dip at the terminal of PMSGs. The proposed scheme changes the current priorities from the active current to the reactive current to inject more reactive power for a severe fault depending on the voltage dip. In addition, the grid-side converter operates in a voltage control mode with the slope, which is the ratio of reactive current capability to the voltage tolerance around a rated value. Moreover, during the fault, the slope is changed depending on the voltage dip to inject more reactive current. The performance of the proposed scheme is validated for a wind power plant consisting of 20 units of 5-MW PMSGs using an EMTP-RV simulator. The results demonstrate that the scheme enables the PMSGs not only to survive during the fault, but also to provide a dynamic reactive power support.

  9. Three-Level Inverters with Common-Mode Voltage Cancellation Based on Synchronous Pulsewidth Modulation

    DEFF Research Database (Denmark)

    Oleschuk, Valentin; Blaabjerg, Frede

    2002-01-01

    A novel method of direct synchronous pulse-width modulation (PWM) is disseminated to three-level voltage source inverters with control algorithms with elimination of the common-mode voltages in three-phase drive systems with PWM. It provides smooth pulses-ratio changing and a quarter-wave symmetry...

  10. Design of a charge pump for high voltage driver applications based on 0.35 μm BCD technology

    Science.gov (United States)

    Zhu, Tiezhu; Zhang, Yuning; Ji, Rendong

    2017-07-01

    Based on the switched capacitor system theory, a new charge pump is designed as the driver of the H-bridge power circuits. The proposed circuit is added with the output feedback control module to realize the steady output, lower the ripple and power noise, and improve the transforming efficiency. Simulation based on 0.35 μm BCD350GE process demonstrates that the circuit has a ripple voltage as low as 200 mV and reaches a high efficiency up to 70% with a load as much as 20 mA when the supply voltage changes from 8 V to 36 V.

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

    DEFF Research Database (Denmark)

    Mucha, Igor

    1999-01-01

    A with a supply voltage down to 1 V, and relatively small device dimensions. In spite of the relatively large signal processing range, the class AB operation of the cell enabled a very low quiescent current consumption, 1 mu A in this design, resulting in a very high current efficiency and effective power......A proposal for a class AB switched current memory cell, suitable for ultra-low-voltage applications is presented. The proposal employs transistors with floating gates, allowing to build analog building blocks for ultralow supply voltage operation also in CMOS processes with high threshold voltages...... current memory cells were designed using a CMOS process with threshold voltages V-T0n = \\V-T0p\\ = 0.9 V for the n- and p-channel devices. Both hand calculations and PSPICE simulations showed that the designed example switched current memory cell allowed a maximum signal range better than +/-18 mu...

  12. Laser restoring the glass surface treated with acid-based paint

    Science.gov (United States)

    Strusevich, Anastasia V.; Poltaev, Yuriy A.; Sinev, Dmitrii A.

    2013-11-01

    The modern city facilities are often being attacked by graffiti artists, and increasingly vandals leave "tags" using paints, which compound based on acids, hydrofluoric or acetic commonly. These paints not only ink the surface, but also increase the surface roughness, and such impact can not be corrected by conventional cleaning. Thus, it was requested to develop technology that would not only clean the surface, but also to restore its structure by smoothing out irregularities and roughness formed after exposure in acid. In this work we investigated the effect of restoring the surface of the glass, spoiled by acid-based paint and then treated with CO2-laser. During the experiments, it was found that it is real to create the single-step laser surface restoring technology.

  13. Integrating Stakeholder Preferences and GIS-Based Multicriteria Analysis to Identify Forest Landscape Restoration Priorities

    Directory of Open Access Journals (Sweden)

    David Uribe

    2014-02-01

    Full Text Available A pressing question that arises during the planning of an ecological restoration process is: where to restore first? Answering this question is a complex task; it requires a multidimensional approach to consider economic constrains and the preferences of stakeholders. Being the problem of spatial nature, it may be explored effectively through Multicriteria Decision Analysis (MCDA performed in a Geographical Information System (GIS environment. The proposed approach is based on the definition and weighting of multiple criteria for evaluating land suitability. An MCDA-based methodology was used to identify priority areas for Forest Landscape Restoration in the Upper Mixtec region, Oaxaca (Mexico, one of the most degraded areas of Latin America. Socioeconomic and environmental criteria were selected and evaluated. The opinions of four different stakeholder groups were considered: general public, academic, Non-governmental organizations (NGOs and governmental officers. The preferences of these groups were spatially modeled to identify their priorities. The final result was a map that identifies the most preferable sites for restoration, where resources and efforts should be concentrated. MCDA proved to be a very useful tool in collective planning, when alternative sites have to be identified and prioritized to guide the restoration work.

  14. Anomalous Threshold Voltage Variability of Nitride Based Charge Storage Nonvolatile Memory Devices

    Directory of Open Access Journals (Sweden)

    Meng Chuan Lee

    2013-01-01

    Full Text Available Conventional technology scaling is implemented to meet the insatiable demand of high memory density and low cost per bit of charge storage nonvolatile memory (NVM devices. In this study, effect of technology scaling to anomalous threshold voltage ( variability is investigated thoroughly on postcycled and baked nitride based charge storage NVM devices. After long annealing bake of high temperature, cell’s variability of each subsequent bake increases within stable distribution and found exacerbate by technology scaling. Apparent activation energy of this anomalous variability was derived through Arrhenius plots. Apparent activation energy (Eaa of this anomalous variability is 0.67 eV at sub-40 nm devices which is a reduction of approximately 2 times from 110 nm devices. Technology scaling clearly aggravates this anomalous variability, and this poses reliability challenges to applications that demand strict control, for example, reference cells that govern fundamental program, erase, and verify operations of NVM devices. Based on critical evidence, this anomalous variability is attributed to lateral displacement of trapped charges in nitride storage layer. Reliability implications of this study are elucidated. Moreover, potential mitigation methods are proposed to complement technology scaling to prolong the front-runner role of nitride based charge storage NVM in semiconductor flash memory market.

  15. Mathematical Derivation of Switching Angles of Multilevel Voltage Source Inverter based on Alternative Phase Opposition Disposition (APOD

    Directory of Open Access Journals (Sweden)

    Ismail Mohd Alif

    2017-01-01

    Full Text Available Modular structured multilevel inverter is very useful for electrical application especially in high voltage and high power applications. The main function of this multilevel inverter is to produce multilevel AC output voltage from several separate DC sources. This project is to derive a newmathematical formulation of multilevel voltage source inverter switching instants. The proposed method for this project is based on the sinusoidal natural sampling PWM (SPWM by comparing several modified modulation signal with a triangular carrier signal. This resulting intersection points between this modulation and carrier signal become the switching instants of the PWM pulses. Derivation also based on Alternative Phase opposition disposition (APOD. A cascaded multilevel inverter is selected as a topology for this project due to major advantages compare with other topology. The derived formula is analyzed by using MATLAB simulation software. It is found that the results that use the derived formula are almost identical to simulation result.

  16. User's guide to the wetland creation/restoration data base, version 2

    Science.gov (United States)

    Miller, Lee; Auble, Gregor T.; Schneller-McDonald, Keith

    1991-01-01

    Wetland creation or restoration projects are frequently proposed as mitigation for unavoidable wetland losses, as components of wetland enhancement programs, and as tools to accomplish specific objectives such as waterfowl production or flood control. There is considerable controversy concerning the effectiveness of such projects as well as the most appropriate and efficient techniques to employ. The importance of the resource and the long time scales involved in fully evaluating a creation or restoration effort make it imperative to consider existing information as fully as possible in the development and evaluation of wetland creation or restoration proposals.To aid in the evaluation of wetland/creation efforts, the U.s. Fish and Wildlife Service (FWS), National Ecology Research Center, has developed the Wetland Creation/Restoration (WCR) Data Base. The data base is a highly indexed or keyworded bibliography of wetland creation or restoration articles. ("Articles" refers to any type of publication that deals specifically with wetland creation/restoration projects or studies.) The scope of the articles is international, although most of them are concerned with projects conducted in the United States. Information coded for each article includes author; citation; type of wetland and its location in terms of state, ecoregion, and FWS region; type of study undertaken; objectives in creating or restoring the wetland; actions performed to realize those objectives; length of time encompassed by the study; evaluation of results and responses to the wetland creation/restoration actions; and a listing of plant species significant to the project. A brief annotation summarizes the article and includes any significant additional information that may not be adequately reflected in the above described fields.Many of these articles describe only one or two components of a total wetland restoration effort. Planning a project that is designed to restore a wetland system (including

  17. Research on a Hierarchical Dynamic Automatic Voltage Control System Based on the Discrete Event-Driven Method

    Directory of Open Access Journals (Sweden)

    Yong Min

    2013-06-01

    Full Text Available In this paper, concepts and methods of hybrid control systems are adopted to establish a hierarchical dynamic automatic voltage control (HD-AVC system, realizing the dynamic voltage stability of power grids. An HD-AVC system model consisting of three layers is built based on the hybrid control method and discrete event-driven mechanism. In the Top Layer, discrete events are designed to drive the corresponding control block so as to avoid solving complex multiple objective functions, the power system’s characteristic matrix is formed and the minimum amplitude eigenvalue (MAE is calculated through linearized differential-algebraic equations. MAE is applied to judge the system’s voltage stability and security and construct discrete events. The Middle Layer is responsible for management and operation, which is also driven by discrete events. Control values of the control buses are calculated based on the characteristics of power systems and the sensitivity method. Then control values generate control strategies through the interface block. In the Bottom Layer, various control devices receive and implement the control commands from the Middle Layer. In this way, a closed-loop power system voltage control is achieved. Computer simulations verify the validity and accuracy of the HD-AVC system, and verify that the proposed HD-AVC system is more effective than normal voltage control methods.

  18. Magnetization Reversal by Out-of-plane Voltage in BiFeO3-based Multiferroic Heterostructures

    Science.gov (United States)

    Wang, J. J.; Hu, J.M.; Peng, Ren-Ci; Gao, Y.; Shen, Y.; Chen, L. Q.; Nan, C. W.

    2015-01-01

    Voltage controlled 180° magnetization reversal has been achieved in BiFeO3-based multiferroic heterostructures, which is promising for the future development of low-power spintronic devices. However, all existing reports involve the use of an in-plane voltage that is unfavorable for practical device applications. Here, we investigate, using phase-field simulations, the out-of-plane (i.e., perpendicular to heterostructures) voltage controlled magnetism in heterostructures consisting of CoFe nanodots and (110) BiFeO3 thin film or island. It is predicted that the in-plane component of the canted magnetic moment at the CoFe/BiFeO3 interface can be reversed repeatedly by applying a perpendicular voltage across the bottom (110) BiFeO3 thin film, which further leads to an in-plane magnetization reversal in the overlaying CoFe nanodot. The non-volatility of such perpendicular voltage controlled magnetization reversal can be achieved by etching the continuous BiFeO3 film into isolated nanoislands with the same in-plane sizes as the CoFe nanodot. The findings would provide general guidelines for future experimental and engineering efforts on developing the electric-field controlled spintronic devices with BiFeO3-based multiferroic heterostructures. PMID:25995062

  19. PSO Based Optimal Location and Sizing of SVC for Novel Multiobjective Voltage Stability Analysis during N – 2 Line Contingency

    Directory of Open Access Journals (Sweden)

    Mangaiyarkarasi S.P.

    2014-12-01

    Full Text Available In this paper voltage stability is analysed based not only on the voltage deviations from the nominal values but also on the number of limit violating buses and severity of voltage limit violations. The expression of the actual state of the system as a numerical index like severity, aids the system operator in taking better security related decisions at control centres both during a period of contingency and also at a highly stressed operating condition. In contrary to conventional N – 1 contingency analysis, Northern Electric Reliability Council (NERC recommends N – 2 line contingency analysis. The decision of the system operator to overcome the present contingency state of the system must blend harmoniously with the stability of the system. Hence the work presents a novel N – 2 contingency analysis based on the continuous severity function of the system. The study is performed on 4005 possible combinations of N – 2 contingency states for the practical Indian Utility 62 bus system. Static VAr Compensator is used to improve voltage profile during line contingencies. A multi- objective optimization with the objective of minimizing the voltage deviation and also the number of limit violating bus with optimal location and optimal sizing of SVC is achieved by Particle Swarm Optimization algorithm.

  20. DC-based smart PV-powered home energy management system based on voltage matching and RF module.

    Science.gov (United States)

    Sabry, Ahmad H; Hasan, W Z W; Ab Kadir, Mza; Radzi, M A M; Shafie, S

    2017-01-01

    The main tool for measuring system efficiency in homes and offices is the energy monitoring of the household appliances' consumption. With the help of GUI through a PC or smart phone, there are various applications that can be developed for energy saving. This work describes the design and prototype implementation of a wireless PV-powered home energy management system under a DC-distribution environment, which allows remote monitoring of appliances' energy consumptions and power rate quality. The system can be managed by a central computer, which obtains the energy data based on XBee RF modules that access the sensor measurements of system components. The proposed integrated prototype framework is characterized by low power consumption due to the lack of components and consists of three layers: XBee-based circuit for processing and communication architecture, solar charge controller, and solar-battery-load matching layers. Six precise analogue channels for data monitoring are considered to cover the energy measurements. Voltage, current and temperature analogue signals were accessed directly from the remote XBee node to be sent in real time with a sampling frequency of 11-123 Hz to capture the possible surge power. The performance shows that the developed prototype proves the DC voltage matching concept and is able to provide accurate and precise results.

  1. Marginal leakage and microhardness evaluation of low-shrinkage resin-based restorative materials.

    Science.gov (United States)

    Hooshmand, Tabassom; Tabari, Negin; Keshvad, Alireza

    2013-01-01

    This study sought to compare the marginal leakage and microhardness of low-shrinkage resin-based dental restorative materials containing ormocer- and silorane-based composites to that of conventional methacrylate-based systems. A total of 50 noncarious extracted human teeth were collected after debridement and standard Class V cavities were prepared. Teeth were randomly assigned to five groups (n = 10) and restored with 5 types of resin-based restorative material composites: hybrid, microhybrid, nanohybrid, ormocer-based, and silorane-based. After thermocycling, all teeth were placed in a silver nitrate solution, sectioned longitudinally in a buccolingual direction, and observed under a stereomicroscope to determine the degree of dye penetration. Data were analyzed using a non-parametric Kruskal-Wallis test (P microhardness test, five specimens were made for each restorative material, using Teflon molds with disk-shaped specimen wells. Specimens were photocured and placed in distilled water (at 37°C) for 24 hours. Vickers Hardness Number (VHN) measurements were performed using a microhardness tester. Data were analyzed by one-way ANOVA and Bonferroni post hoc tests. In terms of microhardness, there was no statistically significant difference among the resin-based restorative materials (P > 0.05). The degree of microleakage at the gingival margins was lowest for the silorane composite, followed by microhybrid and nanohybrid. The silorane composite was significantly lower than that of the ormocer and hybrid composites (P material could provide a marginal seal comparable to that provided by microhybrid or nanohybrid resin composites.

  2. A Rotational Gyroscope with a Water-Film Bearing Based on Magnetic Self-Restoring Effect.

    Science.gov (United States)

    Chen, Dianzhong; Liu, Xiaowei; Zhang, Haifeng; Li, Hai; Weng, Rui; Li, Ling; Rong, Wanting; Zhang, Zhongzhao

    2018-01-31

    Stable rotor levitation is a challenge for rotational gyroscopes (magnetically suspended gyroscopes (MSG) and electrostatically suspended gyroscopes (ESG)) with a ring- or disk-shaped rotor, which restricts further improvement of gyroscope performance. In addition, complicated pick-up circuits and feedback control electronics propose high requirement on fabrication technology. In the proposed gyroscope, a ball-disk shaped rotor is supported by a water-film bearing, formed by centrifugal force to deionized water at the cavity of the lower supporting pillar. Water-film bearing provides stable mechanical support, without the need for complicated electronics and control system for rotor suspension. To decrease sliding friction between the rotor ball and the water-film bearing, a supherhydrophobic surface (SHS) with nano-structures is fabricated on the rotor ball, resulting in a rated spinning speed increase of 12.4% (under the same driving current). Rotor is actuated by the driving scheme of brushless direct current motor (BLDCM). Interaction between the magnetized rotor and the magnetic-conducted stator produces a sinusoidal rotor restoring torque, amplitude of which is proportional to the rotor deflection angle inherently. Utilization of this magnetic restoring effect avoids adding of a high amplitude voltage for electrostatic feedback, which may cause air breakdown. Two differential capacitance pairs are utilized to measure input angular speeds at perpendicular directions of the rotor plane. The bias stability of the fabricated gyroscope is as low as 0.5°/h.

  3. A Rotational Gyroscope with a Water-Film Bearing Based on Magnetic Self-Restoring Effect

    Directory of Open Access Journals (Sweden)

    Dianzhong Chen

    2018-01-01

    Full Text Available Stable rotor levitation is a challenge for rotational gyroscopes (magnetically suspended gyroscopes (MSG and electrostatically suspended gyroscopes (ESG with a ring- or disk-shaped rotor, which restricts further improvement of gyroscope performance. In addition, complicated pick-up circuits and feedback control electronics propose high requirement on fabrication technology. In the proposed gyroscope, a ball-disk shaped rotor is supported by a water-film bearing, formed by centrifugal force to deionized water at the cavity of the lower supporting pillar. Water-film bearing provides stable mechanical support, without the need for complicated electronics and control system for rotor suspension. To decrease sliding friction between the rotor ball and the water-film bearing, a supherhydrophobic surface (SHS with nano-structures is fabricated on the rotor ball, resulting in a rated spinning speed increase of 12.4% (under the same driving current. Rotor is actuated by the driving scheme of brushless direct current motor (BLDCM. Interaction between the magnetized rotor and the magnetic-conducted stator produces a sinusoidal rotor restoring torque, amplitude of which is proportional to the rotor deflection angle inherently. Utilization of this magnetic restoring effect avoids adding of a high amplitude voltage for electrostatic feedback, which may cause air breakdown. Two differential capacitance pairs are utilized to measure input angular speeds at perpendicular directions of the rotor plane. The bias stability of the fabricated gyroscope is as low as 0.5°/h.

  4. Coordination of voltage and reactive power control in the extra high voltage substations based on the example of solutions applied in the national power system

    Directory of Open Access Journals (Sweden)

    Dariusz Kołodziej

    2012-06-01

    Full Text Available This paper presents examples of coordination between automatic voltage and reactive power control systems (ARST covering adjacent and strongly related extra high voltage substations. Included are conclusions resulting from the use of these solutions. The Institute of Power Engineering, Gdańsk Division has developed and deployed ARST systems in the national power system for a dozen or so years.

  5. Graphene nanoribbon based negative resistance device for ultra-low voltage digital logic applications

    Science.gov (United States)

    Khatami, Yasin; Kang, Jiahao; Banerjee, Kaustav

    2013-01-01

    Negative resistance devices offer opportunities in design of compact and fast analog and digital circuits. However, their implementation in logic applications has been limited due to their small ON current to OFF current ratios (peak to valley ratio). In this paper, a design for a 2-port negative resistance device based on arm-chair graphene nanoribbon is presented. The proposed structure takes advantage of electrostatic doping, and offers high ON current (˜700 μA/μm) as well as ON current to OFF current ratio of more than 105. The effects of several design parameters such as doping profile, gate workfunction, bandgap, and hetero-interface characteristics are investigated to improve the performance of the proposed devices. The proposed device offers high flexibility in terms of the design and optimization, and is suitable for digital logic applications. A complementary logic is developed based on the proposed device, which can be operated down to 200 mV of supply voltage. The complementary logic is used in design of an ultra-compact bi-stable switching static memory cell. Due to its compactness and high drive current, the proposed memory cell can outperform the conventional static random access memory cells in terms of switching speed and power consumption.

  6. A high voltage supercapacitor based on ionic liquid with an activated carbon electrode

    Science.gov (United States)

    Pilathottathil, Shabeeba; Thasneema, K. K.; Shahin Thayyil, Mohamed; Pillai, M. P.; Niveditha, C. V.

    2017-07-01

    A symmetric supercapacitor with porous activated carbon as the active material and trihexyl (tetradecyl) phosphonium bis (trifluoromethanesulfonyl) imide [PC6C6C6C14][Tf2N] as the electrolyte was fabricated. Scanning electron microscopy, atomic force microscopy, x-ray diffraction, Fourier transform infrared spectroscopy and a zeta particle size analysis were conducted to examine the surface morphology and other physical properties. Differential scanning calorimetry and a thermal gravimetric analysis were performed to study the thermal stability of the ionic liquid based electrolyte. The binary mixture route was taken with acetonitrile and ionic liquid for reducing the viscosity to enhance the ionic mobility. Cyclic voltammetry, impedance spectroscopy and charge-discharge investigations were conducted to assess the performance of the supercapacitor. A very high specific capacitance of 300 F g-1, an ultra high energy density of 110 Wh kg-1, a high rate scalability (up to 1000 cycles) and an increased operation voltage of 3.5 V were achieved to propose this electrode electrolyte combination as a potential candidate for future ionic liquid based supercapacitor.

  7. Atmospheric pressure plasma jet with high-voltage power supply based on piezoelectric transformer.

    Science.gov (United States)

    Babij, Michał; Kowalski, Zbigniew W; Nitsch, Karol; Silberring, Jerzy; Gotszalk, Teodor

    2014-05-01

    The dielectric barrier discharge plasma jet, an example of the nonthermal atmospheric pressure plasma jet (APPJ), generates low-temperature plasmas that are suitable for the atomization of volatile species and can also be served as an ionization source for ambient mass and ion mobility spectrometry. A new design of APPJ for mass spectrometry has been built in our group. In these plasma sources magnetic transformers (MTs) and inductors are typically used in power supplies but they present several drawbacks that are even more evident when dealing with high-voltage normally used in APPJs. To overcome these disadvantages, high frequency generators with the absence of MT are proposed in the literature. However, in the case of miniaturized APPJs these conventional power converters, built of ferromagnetic cores and inductors or by means of LC resonant tank circuits, are not so useful as piezoelectric transformer (PT) based power converters due to bulky components and small efficiency. We made and examined a novel atmospheric pressure plasma jet with PT supplier served as ionization source for ambient mass spectrometry, and especially mobile spectrometry where miniaturization, integration of components, and clean plasma are required. The objective of this paper is to describe the concept, design, and implementation of this miniaturized piezoelectric transformer-based atmospheric pressure plasma jet.

  8. Accountability to Public Stakeholders in Watershed-Based Restoration

    Science.gov (United States)

    There is an increasing push at the federal, state, and local levels for watershed-based conservation projects. These projects work to address water quality issues in degraded waterways through the implementation of a suite of best management practices on land throughout a watersh...

  9. Cross-layer restoration with software defined networking based on IP over optical transport networks

    Science.gov (United States)

    Yang, Hui; Cheng, Lei; Deng, Junni; Zhao, Yongli; Zhang, Jie; Lee, Young

    2015-10-01

    The IP over optical transport network is a very promising networking architecture applied to the interconnection of geographically distributed data centers due to the performance guarantee of low delay, huge bandwidth and high reliability at a low cost. It can enable efficient resource utilization and support heterogeneous bandwidth demands in highly-available, cost-effective and energy-effective manner. In case of cross-layer link failure, to ensure a high-level quality of service (QoS) for user request after the failure becomes a research focus. In this paper, we propose a novel cross-layer restoration scheme for data center services with software defined networking based on IP over optical network. The cross-layer restoration scheme can enable joint optimization of IP network and optical network resources, and enhance the data center service restoration responsiveness to the dynamic end-to-end service demands. We quantitatively evaluate the feasibility and performances through the simulation under heavy traffic load scenario in terms of path blocking probability and path restoration latency. Numeric results show that the cross-layer restoration scheme improves the recovery success rate and minimizes the overall recovery time.

  10. A prototype Knowledge-Based System to Aid Space System Restoration Management.

    Science.gov (United States)

    1986-12-01

    to those outlined above for a space system restoration management system. 28 111,-.2-6 * ,* IV. Arificial Intelligence Knowledge-based Systems... vision ), natural language understanding and expert problem solving (35:3). In the early days of AI, researchers tried to simulate " the complicated process

  11. Teacher Consultation to Enhance Implementation of School-Based Restorative Justice

    Science.gov (United States)

    Mayworm, Ashley M.; Sharkey, Jill D.; Hunnicutt, Kayleigh L.; Schiedel, K. Chris

    2016-01-01

    Restorative justice (RJ) is an alternative approach to school discipline that has been gaining recognition in the public and academic spheres as a way to engage students who misbehave in school. RJ has promise to address racial/ethnic, gender, and disability disproportionality in school discipline. One aspect of school-based RJ that has received…

  12. Chebyshev-based technique for automated restoration of digital copies of faded photographic prints

    Science.gov (United States)

    Uchaev, Dmitry V.; Uchaev, Denis V.; Malinnikov, Vasiliy A.

    2017-01-01

    We present a technique for automated restoration of digital images obtained from faded photographic prints. The proposed defading technique uses our early proposed image contrast enhancement algorithm based on a contrast measure of images in the Chebyshev moment transform domain. Obtained experimental results demonstrate some advantages of the technique as compared to other widely used image enhancement methods.

  13. Multi-scale retinex with color restoration image enhancement based on Gaussian filtering and guided filtering

    Science.gov (United States)

    Ma, Jinxiang; Fan, Xinnan; Ni, Jianjun; Zhu, Xifang; Xiong, Chao

    2017-07-01

    In order to restore image color and enhance contrast of remote sensing image without suffering from color cast and insufficient detail enhancement, a novel improved multi-scale retinex with color restoration (MSRCR) image enhancement algorithm based on Gaussian filtering and guided filtering was proposed in this paper. Firstly, multi-scale Gaussian filtering functions were used to deal with the original image to obtain the rough illumination components. Secondly, accurate illumination components were acquired by using the guided filtering functions. Then, combining with four-direction Sobel edge detector, a self-adaptive weight selection nonlinear image enhancement was carried out. Finally, a series of evaluate metrics such as mean, MSE, PSNR, contrast and information entropy were used to assess the enhancement algorithm. The results showed that the proposed algorithm can suppress effectively noise interference, enhance the image quality and restore image color effectively.

  14. Microleakage of silorane- and methacrylate-based class V composite restorations.

    Science.gov (United States)

    Krifka, Stephanie; Federlin, Marianne; Hiller, Karl-Anton; Schmalz, Gottfried

    2012-08-01

    The marginal integrity of class V restorations in a silorane- and a group of methacrylate-based composite resins with varying viscosities was tested in the present study. Different adhesives (OptiBond FL, KerrHawe; AdheSE One, Vivadent; or Silorane System Adhesive, 3M ESPE) were applied to 168 standardized class V cavities. The cavities (n = 12) were filled with a wide range of different viscous composite resins: Filtek Silorane, 3M ESPE; els and els flow, Saremco; Tetric EvoCeram and Tetric EvoFlow, Vivadent; Grandio, Voco; and Ultraseal XT Plus, Ultradent. Microleakage of the restoration was assessed by dye penetration (silver staining) on multiple sections with and without thermocycling and mechanical loading (TCML: 5,000 × 5-55°C; 30 s/cycle; 500,000 × 72.5 N, 1.6 Hz). Data were statistically analyzed with the Mann-Whitney U test and the Error Rates Method (ERM). The silorane-based composite resin yielded the lowest dye penetration after TCML. Microleakage of methacrylate-based composite restorations, in general (ERM), was statistically significantly influenced by the adhesive system, Moreover, dye penetration at enamel margins was significantly lower than dye penetration at dentin margins. The chemical basis of composite resins and adjacent tooth substance seems to strongly influence marginal sealing of class V restorations for methacrylate-based materials. Moreover, the steps of dental adhesives used affected marginal integrity. The silorane-based composite resin evaluated in the present study exhibits the best marginal seal. The three-step adhesive yielded better marginal sealing than the one-step adhesive for methacrylate-based class V composite restorations.

  15. Fault Characteristics and Control Strategies of Multiterminal High Voltage Direct Current Transmission Based on Modular Multilevel Converter

    Directory of Open Access Journals (Sweden)

    Fei Chang

    2015-01-01

    Full Text Available The modular multilevel converter (MMC is an emerging voltage source converter topology suitable for multiterminal high voltage direct current transmission based on modular multilevel converter (MMC-MTDC. This paper presents fault characteristics of MMC-MTDC including submodule fault, DC line fault, and fault ride-through of wind farm integration. Meanwhile, the corresponding protection strategies are proposed. The correctness and effectiveness of the control strategies are verified by establishing a three-terminal MMC-MTDC system under the PSCAD/EMTDC electromagnetic transient simulation environment.

  16. Capacitance Estimation Algorithm based on DC-Link Voltage Harmonics Using ANN in Three-Phase Motor Drive Systems

    DEFF Research Database (Denmark)

    Soliman, Hammam Abdelaal Hammam; Davari, Pooya; Wang, Huai

    2017-01-01

    to industry. In this digest, a condition monitoring methodology that estimates the capacitance value of the dc-link capacitor in a three phase Front-End diode bridge motor drive is proposed. The proposed software methodology is based on Artificial Neural Network (ANN) algorithm. The harmonics of the dc......-link voltage are used as training data to the Artificial Neural Network. Fast Fourier Transform (FFT) of the dc-link voltage is analysed in order to study the impact of capacitance variation on the harmonics order. Laboratory experiments are conducted to validate the proposed methodology and the error analysis...

  17. Index-Based Assessment of Voltage Rise and Reverse Power Flow Phenomena in a Distribution Feeder Under High PV Penetration

    DEFF Research Database (Denmark)

    Hasheminamin, Maryam; Agelidis, Vassilios G.; Salehi, Vahid

    2015-01-01

    The proliferation of photovoltaic (PV) generation in low- and medium-voltage distribution networks is expected to continue. Qualified studies can quantify adverse impacts of high PV penetration on distribution networks and assist utilities in decision making. This paper proposes an index-based me......The proliferation of photovoltaic (PV) generation in low- and medium-voltage distribution networks is expected to continue. Qualified studies can quantify adverse impacts of high PV penetration on distribution networks and assist utilities in decision making. This paper proposes an index...... are used to confirm the effectiveness of the proposed indices. This paper derives the acceptable range of the proposed indices and safe margin, which have been compared with the basic active power curtailment method with no constraint, in order to avoid voltage rise. The IEEE 69-bus network is also...

  18. Coordinated control of a DFIG-based wind-power generation system with SGSC under distorted grid voltage conditions

    DEFF Research Database (Denmark)

    Yao, Jun; Li, Qing; Chen, Zhe

    2013-01-01

    This paper presents a coordinated control method for a doubly-fed induction generator (DFIG)-based wind-power generation system with a series grid-side converter (SGSC) under distorted grid voltage conditions. The detailed mathematical models of the DFIG system with SGSC are developed in the mult...

  19. Uncertainty in real-time voltage stability assessment methods based on Thevenin equivalent due to PMU’s accuracy

    DEFF Research Database (Denmark)

    Perez, Angel; Møller, Jakob Glarbo; Jóhannsson, Hjörtur

    2014-01-01

    This article studies the influence of PMU’s accuracy in voltage stability assessment, considering the specific case of Th ́ evenin equivalent based methods that include wide-area information in its calculations. The objective was achieved by producing a set of synthesized PMU measurements from...

  20. FDI based on Artificial Neural Network for Low-Voltage-Ride-Through in DFIG-based Wind Turbine.

    Science.gov (United States)

    Adouni, Amel; Chariag, Dhia; Diallo, Demba; Ben Hamed, Mouna; Sbita, Lassaâd

    2016-09-01

    As per modern electrical grid rules, Wind Turbine needs to operate continually even in presence severe grid faults as Low Voltage Ride Through (LVRT). Hence, a new LVRT Fault Detection and Identification (FDI) procedure has been developed to take the appropriate decision in order to develop the convenient control strategy. To obtain much better decision and enhanced FDI during grid fault, the proposed procedure is based on voltage indicators analysis using a new Artificial Neural Network architecture (ANN). In fact, two features are extracted (the amplitude and the angle phase). It is divided into two steps. The first is fault indicators generation and the second is indicators analysis for fault diagnosis. The first step is composed of six ANNs which are dedicated to describe the three phases of the grid (three amplitudes and three angle phases). Regarding to the second step, it is composed of a single ANN which analysis the indicators and generates a decision signal that describes the function mode (healthy or faulty). On other hand, the decision signal identifies the fault type. It allows distinguishing between the four faulty types. The diagnosis procedure is tested in simulation and experimental prototype. The obtained results confirm and approve its efficiency, rapidity, robustness and immunity to the noise and unknown inputs. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  1. Modeling and Control of a DFIG-Based Wind Turbine During a Grid Voltage Drop

    OpenAIRE

    M. Shahabi; S. Asghar Gholamian; A. Babaie Lajimi

    2011-01-01

    Doubly-fed induction generators (DFIG) are widely used in wind energy generation systems. During a grid voltage drop, performance is degraded with rotor over current deteriorating the fault-ride through (FRT) capability of the DFIG wind-energy generation system. In this paper, a complete mathematical DFIG model is proposed. The rotor is considered fed by a voltage source converter whereas the stator is connected to the grid directly. Output power and electromagnetic torque are controlled usin...

  2. Restorative treatment thresholds for interproximal primary caries based on radiographic images: findings from the Dental Practice-Based Research Network.

    Science.gov (United States)

    Gordan, Valeria V; Garvan, Cynthia W; Heft, Marc W; Fellows, Jeffrey L; Qvist, Vibeke; Rindal, D Brad; Gilbert, Gregg H

    2009-01-01

    This study sought to quantify the depths of proximal caries lesions that lead dentists in regular clinical practice to intervene restoratively, based on hypothetical scenarios that present radiographic images and patient background information, and to identify characteristics associated with restorative intervention in lesions that have penetrated only the enamel surface. This study surveyed dentists from the Dental Practice-Based Research Network (DPBRN) who had reported doing at least some restorative dentistry (n = 901). Dentists were asked to indicate the depth at which they would restore a lesion, based on a series of radiographic images depicting interproximal caries at increasing lesion depths in a mandibular premolar; in addition, the dentists were questioned regarding two caries risk scenarios: one involving a patient with low caries risk and another involving a patient at higher risk. Logistic regression was used to analyze associations between the decision to intervene restoratively and specific dentist, practice, and patient characteristics. Of the 901 DPBRN practitioner-investigators, 500 (56%) completed the survey. For a high caries risk patient, 66% of respondents indicated that they would restore a proximal enamel lesion, while 24% would do so once the lesion had reached into the outer third of the dentin. For a low caries risk patient, 39% of respondents reported that they would restore an enamel lesion, and 54% would do so once the lesion had reached into the outer third of the dentin. In multivariate analyses that accounted for dentist and practice characteristics, dentists in large group practices were less likely to intervene surgically for enamel caries, regardless of patient's caries risk.

  3. Aqueous based asymmetrical-bipolar electrochemical capacitor with a 2.4 V operating voltage

    Science.gov (United States)

    Wu, Haoran; Lian, Keryn

    2018-02-01

    A novel asymmetrical-bipolar electrochemical capacitor system leveraging the contributions of a Zn-CNT asymmetrical electrode and a KOH-H2SO4 dual-pH electrolyte was developed. The positive and negative electrodes operated in electrolytes with different pH, exploiting the maximum potential of both electrodes, which led to a cell voltage of 2.4 V. The potential tracking of both electrodes revealed that the Zn negative electrode could maintain a potential at -1.2 V, while the CNT positive electrode can be charged to +1.2 V without significant irreversible reactions. A bipolar ion exchange membrane has effectively separated the acid and alkaline from neutralization, which resulted in stable performance of the device with capacitance retention of 94% and coulombic efficiency of 99% over 10,000 cycles. This asymmetrical-bipolar design overcomes the thermodynamic limit of water decomposition, opening a new avenue towards high energy and high power density aqueous-based ECs.

  4. DG Allocation Based on Reliability, Losses and Voltage Sag Considerations: an expert system approach

    Directory of Open Access Journals (Sweden)

    Sahar Abdel Moneim Moussa

    2017-03-01

    Full Text Available Expert System (ES as a branch of Artificial Intelligence (AI methodology can potentially help in solving complicated power system problems. This may be more appropriate methodology than conventional optimization techniques when contradiction between objectives appears in reaching the optimum solution. When this contradiction is the hindrance in reaching the required system operation through the application of traditional methods ES can give a hand in such case. In this paper, the  knowledge- based ES technique is proposed to reach near-optimum solution which is further directed to the optimum solution through particle swarm optimization (PSO technique. This idea is known as Hybrid-Expert-System (HES. The proposed idea is used in getting the optimum allocation of a number of distributed generation (DG units on Distribution System (DS busbars taking into consideration three issues; reliability, voltage sag, and line losses. Optimality is assessed on the economic basis by calculating money benefits (or losses resulting from DG addition considering the three aforementioned issues. The effectiveness of the proposed technique is ascertained through example.

  5. Multi-link faults localization and restoration based on fuzzy fault set for dynamic optical networks.

    Science.gov (United States)

    Zhao, Yongli; Li, Xin; Li, Huadong; Wang, Xinbo; Zhang, Jie; Huang, Shanguo

    2013-01-28

    Based on a distributed method of bit-error-rate (BER) monitoring, a novel multi-link faults restoration algorithm is proposed for dynamic optical networks. The concept of fuzzy fault set (FFS) is first introduced for multi-link faults localization, which includes all possible optical equipment or fiber links with a membership describing the possibility of faults. Such a set is characterized by a membership function which assigns each object a grade of membership ranging from zero to one. OSPF protocol extension is designed for the BER information flooding in the network. The BER information can be correlated to link faults through FFS. Based on the BER information and FFS, multi-link faults localization mechanism and restoration algorithm are implemented and experimentally demonstrated on a GMPLS enabled optical network testbed with 40 wavelengths in each fiber link. Experimental results show that the novel localization mechanism has better performance compared with the extended limited perimeter vector matching (LVM) protocol and the restoration algorithm can improve the restoration success rate under multi-link faults scenario.

  6. Applying trait-based models to achieve functional targets for theory-driven ecological restoration.

    Science.gov (United States)

    Laughlin, Daniel C

    2014-07-01

    Manipulating community assemblages to achieve functional targets is a key component of restoring degraded ecosystems. The response-and-effect trait framework provides a conceptual foundation for translating restoration goals into functional trait targets, but a quantitative framework has been lacking for translating trait targets into assemblages of species that practitioners can actually manipulate. This study describes new trait-based models that can be used to generate ranges of species abundances to test theories about which traits, which trait values and which species assemblages are most effective for achieving functional outcomes. These models are generalisable, flexible tools that can be widely applied across many terrestrial ecosystems. Examples illustrate how the framework generates assemblages of indigenous species to (1) achieve desired community responses by applying the theories of environmental filtering, limiting similarity and competitive hierarchies, or (2) achieve desired effects on ecosystem functions by applying the theories of mass ratios and niche complementarity. Experimental applications of this framework will advance our understanding of how to set functional trait targets to achieve the desired restoration goals. A trait-based framework provides restoration ecology with a robust scaffold on which to apply fundamental ecological theory to maintain resilient and functioning ecosystems in a rapidly changing world. © 2014 John Wiley & Sons Ltd/CNRS.

  7. Color Restoration of RGBN Multispectral Filter Array Sensor Images Based on Spectral Decomposition

    Directory of Open Access Journals (Sweden)

    Chulhee Park

    2016-05-01

    Full Text Available A multispectral filter array (MSFA image sensor with red, green, blue and near-infrared (NIR filters is useful for various imaging applications with the advantages that it obtains color information and NIR information simultaneously. Because the MSFA image sensor needs to acquire invisible band information, it is necessary to remove the IR cut-offfilter (IRCF. However, without the IRCF, the color of the image is desaturated by the interference of the additional NIR component of each RGB color channel. To overcome color degradation, a signal processing approach is required to restore natural color by removing the unwanted NIR contribution to the RGB color channels while the additional NIR information remains in the N channel. Thus, in this paper, we propose a color restoration method for an imaging system based on the MSFA image sensor with RGBN filters. To remove the unnecessary NIR component in each RGB color channel, spectral estimation and spectral decomposition are performed based on the spectral characteristics of the MSFA sensor. The proposed color restoration method estimates the spectral intensity in NIR band and recovers hue and color saturation by decomposing the visible band component and the NIR band component in each RGB color channel. The experimental results show that the proposed method effectively restores natural color and minimizes angular errors.

  8. Color Restoration of RGBN Multispectral Filter Array Sensor Images Based on Spectral Decomposition.

    Science.gov (United States)

    Park, Chulhee; Kang, Moon Gi

    2016-05-18

    A multispectral filter array (MSFA) image sensor with red, green, blue and near-infrared (NIR) filters is useful for various imaging applications with the advantages that it obtains color information and NIR information simultaneously. Because the MSFA image sensor needs to acquire invisible band information, it is necessary to remove the IR cut-offfilter (IRCF). However, without the IRCF, the color of the image is desaturated by the interference of the additional NIR component of each RGB color channel. To overcome color degradation, a signal processing approach is required to restore natural color by removing the unwanted NIR contribution to the RGB color channels while the additional NIR information remains in the N channel. Thus, in this paper, we propose a color restoration method for an imaging system based on the MSFA image sensor with RGBN filters. To remove the unnecessary NIR component in each RGB color channel, spectral estimation and spectral decomposition are performed based on the spectral characteristics of the MSFA sensor. The proposed color restoration method estimates the spectral intensity in NIR band and recovers hue and color saturation by decomposing the visible band component and the NIR band component in each RGB color channel. The experimental results show that the proposed method effectively restores natural color and minimizes angular errors.

  9. Mechanical properties of four methylmethacrylate-based resins for provisional fixed restorations.

    Science.gov (United States)

    Hernandez, E P; Oshida, Y; Platt, J A; Andres, C J; Barco, M T; Brown, D T

    2004-01-01

    The use of a provisional restoration is an important phase in the treatment of the dental prosthetic patient. A good provisional restoration should satisfy the following requirements: pulpal protection, positional stability, ease in cleaning, accurate margins, wear resistance, dimensional stability, and serve as a diagnostic aid in treatment assessment and esthetics. There is a tendency for discoloration, occlusal wear, and fracture that eventually leads to unnecessary repair. Heat-processed and reinforced methacrylate-based resins have been used to improve the mechanical and physical properties of provisional restorations. Among various improvements, the interpenetrating network crosslinked PMMA (IPN) has been shown to have superior mechanical properties if manufactured through a dough compression molding process at 130 degrees C. However, there have been no published data that relate with the use of this material for fixed provisional restorations. The objective of this study was to compare four methyl methacrylate-based resins for provisional crowns and bridges with varying processing cycles, including JET [self-cure], ACRALON [heat-cured], titanium dioxide filled PMMA [heat-cured], and IPN [heat-cured denture tooth resin]. Properties studied included transverse strength, toughness, rigidity, and hardness. From the results of this study the following conclusions can be made: the IPN group may have had a lower degree of conversion as demonstrated by decreased strength, toughness, and hardness data as compared with Acralon. Increasing the polymerization cycle of unmodified Acralon resin causes a significant increase in strength.

  10. Postoperative Hypersensitivity in Class I Resin-based Composite Restorations in General Practice: Interim Results

    OpenAIRE

    Berkowitz, Gary S.; Horowitz, Allan J.; Curro, Fredrick A.; Craig, Ronald G.; Ship, Jonathan A.; Vena, Donald A.; Thompson, P.

    2009-01-01

    Posterior permanent teeth with carious lesions radiographically extending no farther than halfway into dentin (n = 565) were restored using a resin-based composite by 38 dentists in a practice-based research network. Preoperative and 1-, 4-, and 13-week-posttreatment hypersensitivity was recorded using an 11-point visual analog scale filled out anonymously by subjects. Analyses were conducted to determine whether any correlation or association existed among several variables, including degree...

  11. Restorative treatment thresholds for interproximal primary caries based on radiographic images: findings from the Dental Practice-Based Research Network

    DEFF Research Database (Denmark)

    Gordan, Valeria V; Garvan, Cynthia W; Heft, Marc W

    2009-01-01

    This study sought to quantify the depths of proximal caries lesions that lead dentists in regular clinical practice to intervene restoratively, based on hypothetical scenarios that present radiographic images and patient background information, and to identify characteristics associated...... that they would restore a proximal enamel lesion, while 24% would do so once the lesion had reached into the outer third of the dentin. For a low caries risk patient, 39% of respondents reported that they would restore an enamel lesion, and 54% would do so once the lesion had reached into the outer third...... a lesion, based on a series of radiographic images depicting interproximal caries at increasing lesion depths in a mandibular premolar; in addition, the dentists were questioned regarding two caries risk scenarios: one involving a patient with low caries risk and another involving a patient at higher risk...

  12. Biophysical characterization of the fluorescent protein voltage probe VSFP2.3 based on the voltage-sensing domain of Ci-VSP

    DEFF Research Database (Denmark)

    Lundby, Alicia; Akemann, Walther; Knöpfel, Thomas

    2010-01-01

    as a monomer. We fused the voltage-sensing domain of Ci-VSP to a pair of fluorescent reporter proteins to generate a genetically encodable voltage-sensing fluorescent probe, VSFP2.3. VSFP2.3 is a fluorescent voltage probe that reports changes in membrane potential as a FRET (fluorescence resonance energy....... Neutralization of an arginine in S4, previously suggested to be a sensing charge, and measuring associated sensing currents indicate that this charge is likely to reside at the membrane-aqueous interface rather than within the membrane electric field. The data presented give us insights into the voltage......-sensing mechanism of Ci-VSP, which will allow us to further improve the sensitivity and kinetics of the family of VSFP proteins....

  13. Encapsulating Non-Human Primate Multipotent Stromal Cells in Alginate via High Voltage for Cell-Based Therapies and Cryopreservation

    Science.gov (United States)

    Gryshkov, Oleksandr; Pogozhykh, Denys; Hofmann, Nicola; Pogozhykh, Olena; Mueller, Thomas; Glasmacher, Birgit

    2014-01-01

    Alginate cell-based therapy requires further development focused on clinical application. To assess engraftment, risk of mutations and therapeutic benefit studies should be performed in an appropriate non-human primate model, such as the common marmoset (Callithrix jacchus). In this work we encapsulated amnion derived multipotent stromal cells (MSCs) from Callithrix jacchus in defined size alginate beads using a high voltage technique. Our results indicate that i) alginate-cell mixing procedure and cell concentration do not affect the diameter of alginate beads, ii) encapsulation of high cell numbers (up to 10×106 cells/ml) can be performed in alginate beads utilizing high voltage and iii) high voltage (15–30 kV) does not alter the viability, proliferation and differentiation capacity of MSCs post-encapsulation compared with alginate encapsulated cells produced by the traditional air-flow method. The consistent results were obtained over the period of 7 days of encapsulated MSCs culture and after cryopreservation utilizing a slow cooling procedure (1 K/min). The results of this work show that high voltage encapsulation can further be maximized to develop cell-based therapies with alginate beads in a non-human primate model towards human application. PMID:25259731

  14. Frequency and voltage dependent electrical responses of poly(triarylamine thin film-based organic Schottky diode

    Directory of Open Access Journals (Sweden)

    Mohamad Khairul Anuar

    2017-01-01

    Full Text Available A metal-organic-metal (MOM type Schottky diode based on poly (triarylamine (PTAA thin films has been fabricated by using the spin coating method. Investigation of the frequency dependent conductance-voltage (G-V-f and capacitance-voltage (C-V-f characteristics of the ITO/PTAA/Al MOM type diode were carried out in the frequency range from 12 Hz to 100 kHz using an LCR meter at room temperature. The frequency and bias voltage dependent electrical response were determined by admittance-based measured method in terms of an equivalent circuit model of the parallel combination of resistance and capacitance (RC circuit. Investigation revealed that the conductance is frequency and a bias voltage dependent in which conductance continuous increase as the increasing frequency, respectively. Meanwhile, the capacitance is dependent on frequency up to a certain value of frequency (100 Hz but decreases at high frequency (1 – 10 kHz. The interface state density in the Schottky diode was determined from G-V and C-V characteristics. The interface state density has values almost constant of 2.8 x 1012 eV−1cm−2 with slightly decrease by increasing frequencies. Consequently, both series resistance and interface trap density were found to decrease with increasing frequency. The frequency dependence of the electrical responses is attributed the distribution density of interface states that could follow the alternating current (AC signal.

  15. Frequency and voltage dependent electrical responses of poly(triarylamine) thin film-based organic Schottky diode

    Science.gov (United States)

    Anuar Mohamad, Khairul; Tak Hoh, Hang; Alias, Afishah; Ghosh, Bablu Kumar; Fukuda, Hisashi

    2017-11-01

    A metal-organic-metal (MOM) type Schottky diode based on poly (triarylamine) (PTAA) thin films has been fabricated by using the spin coating method. Investigation of the frequency dependent conductance-voltage (G-V-f) and capacitance-voltage (C-V-f) characteristics of the ITO/PTAA/Al MOM type diode were carried out in the frequency range from 12 Hz to 100 kHz using an LCR meter at room temperature. The frequency and bias voltage dependent electrical response were determined by admittance-based measured method in terms of an equivalent circuit model of the parallel combination of resistance and capacitance (RC circuit). Investigation revealed that the conductance is frequency and a bias voltage dependent in which conductance continuous increase as the increasing frequency, respectively. Meanwhile, the capacitance is dependent on frequency up to a certain value of frequency (100 Hz) but decreases at high frequency (1 - 10 kHz). The interface state density in the Schottky diode was determined from G-V and C-V characteristics. The interface state density has values almost constant of 2.8 x 1012 eV-1cm-2 with slightly decrease by increasing frequencies. Consequently, both series resistance and interface trap density were found to decrease with increasing frequency. The frequency dependence of the electrical responses is attributed the distribution density of interface states that could follow the alternating current (AC) signal.

  16. Inside the "Black Box" of River Restoration: Using Catchment History to Identify Disturbance and Response Mechanisms to Set Targets for Process-Based Restoration

    Directory of Open Access Journals (Sweden)

    Sarah Mika

    2010-12-01

    Full Text Available Many river restoration projects fail. Inadequate project planning underpins many of the reasons given for failure (such as setting overly ambitious goals; selecting inappropriate sites and techniques; losing stakeholder motivation; and neglecting to monitor, assess, and document projects. Another major problem is the lack of an agreed guiding image to direct the activities aimed at restoring the necessary biophysical and ecological processes within the logistic constraints of on-ground works. Despite a rich literature defining the components of restoration project planning, restoration ecology currently lacks an explicit and logical means of moving from the initial project vision through to on-ground strategies. Yet this process is fundamental because it directly links the ecological goals of the project to the on-ground strategies used to achieve them. We present a planning process that explicitly uses an interdisciplinary mechanistic model of disturbance drivers and system responses to build from the initial project vision to the implementation of on-ground works. A worked example on the Upper Hunter River in southeastern Australia shows how understanding catchment history can reveal disturbance and response mechanisms, thus facilitating process-based restoration.

  17. Investigation of Voltage Control at Consumers Connection Points Based on Smart Approach

    Directory of Open Access Journals (Sweden)

    Artem Vanin

    2016-07-01

    Full Text Available More and more functions are performed automatically with the use of various electrical appliances and sophisticated control systems in all spheres of human life. In this regard, the demand for reliable and quality power supply is increasing. To date, low power quality, in particular unacceptable voltage levels, is an important deterrent for introducing technologies of smart electricity consumers (smart homes, smart companies, smart cities. This paper presents a comprehensive solution of this problem with the use of a voltage control system in the distribution grids, which is oriented on grids with a large number of heterogeneous loads and low level of Information Technology (IT penetration. It is proposed to be installed on distribution substation special devices that perform continuous measurements of voltage levels, produce short-term forecasts and transmit the permissible ranges of voltage control to the power supply centers. The computing unit at the primary substation analyzes the data received from all distribution substations, and determines the optimum control actions to meet the requirements of all consumers. The proposed system was compared with conventional voltage control methods. The results have proved the effectiveness of the proposed approach.

  18. Improving the output voltage waveform of an intense electron-beam accelerator based on helical type Blumlein pulse forming line

    Directory of Open Access Journals (Sweden)

    Xin-Bing Cheng

    2010-07-01

    Full Text Available The Blumlein pulse forming line (BPFL consisting of an inner coaxial pulse forming line (PFL and an outer coaxial PFL is widely used in the field of pulsed power, especially for intense electron-beam accelerators (IEBA. The output voltage waveform determines the quality and characteristics of the output beam current of the IEBA. Comparing with the conventional BPFL, an IEBA based on a helical type BPFL can increase the duration of the output voltage in the same geometrical volume. However, for the helical type BPFL, the voltage waveform on a matched load may be distorted which influences the electron-beam quality. In this paper, an IEBA based on helical type BPFL is studied theoretically. Based on telegrapher equations of the BPFL, a formula for the output voltage of IEBA is obtained when the transition section is taken into account, where the transition section is between the middle cylinder of BPFL and the load. From the theoretical analysis, it is found that the wave impedance and transit time of the transition section influence considerably the main pulse voltage waveform at the load, a step is formed in front of the main pulse, and a sharp spike is also formed at the end of the main pulse. In order to get a well-shaped square waveform at the load and to improve the electron-beam quality of such an accelerator, the wave impedance of the transition section should be equal to that of the inner PFL of helical type BPFL and the transit time of the transition section should be designed as short as possible. Experiments performed on an IEBA with the helical type BPFL show reasonable agreement with theoretical analysis.

  19. A SVPWM based on fluctuate capacitor voltage in 3L-NPC back-to-back converter applied to wind energy

    DEFF Research Database (Denmark)

    Chen, Quan; Wang, Qunjing; Chen, Zhe

    2014-01-01

    ' voltage, will cause variations of the voltage vector and the dwell time distribution in the synthesizing algorithm. In this paper a novel space vector PWM (SVPWM) for back-to-back 3L-NPC converter when unbalanced neutral point potential occurring is proposed. An error factor based on the difference...... between the fluctuate voltage of upper and lower capacitors is extracted. Based on this error factor the duty-time of every active voltage vector is calculated. In order to validate the model and the control strategy proposed in this paper, a 2MW 3L-NPC converter used in wind energy has been simulated....

  20. Simulation of Drastic Lag Phenomena in GaAs-Based FETs for Large Voltage Swing

    Directory of Open Access Journals (Sweden)

    K. Horio

    2001-01-01

    Full Text Available Turn-on characteristics of GaAs MESFETs and HEMTs are simulated when the gate voltage is changed abruptly. The gate-lag or slow current transient becomes more pronounced when the off-state gate voltage is more negative, because the surface-state effects or substrate-trap effects become more significant. Changes of I–V curves of GaAs MESFETs, when the drain voltage is swept with different speeds, are also simulated. When the swept time is short, the curve shows overshoot-like behavior and the kink disappears, indicating that the I–V characteristics should be quite different between DC and RF conditions.

  1. An Autonomous Connectivity Restoration Algorithm Based on Finite State Machine for Wireless Sensor-Actor Networks.

    Science.gov (United States)

    Zhang, Ying; Wang, Jun; Hao, Guan

    2018-01-08

    With the development of autonomous unmanned intelligent systems, such as the unmanned boats, unmanned planes and autonomous underwater vehicles, studies on Wireless Sensor-Actor Networks (WSANs) have attracted more attention. Network connectivity algorithms play an important role in data exchange, collaborative detection and information fusion. Due to the harsh application environment, abnormal nodes often appear, and the network connectivity will be prone to be lost. Network self-healing mechanisms have become critical for these systems. In order to decrease the movement overhead of the sensor-actor nodes, an autonomous connectivity restoration algorithm based on finite state machine is proposed. The idea is to identify whether a node is a critical node by using a finite state machine, and update the connected dominating set in a timely way. If an abnormal node is a critical node, the nearest non-critical node will be relocated to replace the abnormal node. In the case of multiple node abnormality, a regional network restoration algorithm is introduced. It is designed to reduce the overhead of node movements while restoration happens. Simulation results indicate the proposed algorithm has better performance on the total moving distance and the number of total relocated nodes compared with some other representative restoration algorithms.

  2. CT image sequence restoration based on sparse and low-rank decomposition.

    Directory of Open Access Journals (Sweden)

    Shuiping Gou

    Full Text Available Blurry organ boundaries and soft tissue structures present a major challenge in biomedical image restoration. In this paper, we propose a low-rank decomposition-based method for computed tomography (CT image sequence restoration, where the CT image sequence is decomposed into a sparse component and a low-rank component. A new point spread function of Weiner filter is employed to efficiently remove blur in the sparse component; a wiener filtering with the Gaussian PSF is used to recover the average image of the low-rank component. And then we get the recovered CT image sequence by combining the recovery low-rank image with all recovery sparse image sequence. Our method achieves restoration results with higher contrast, sharper organ boundaries and richer soft tissue structure information, compared with existing CT image restoration methods. The robustness of our method was assessed with numerical experiments using three different low-rank models: Robust Principle Component Analysis (RPCA, Linearized Alternating Direction Method with Adaptive Penalty (LADMAP and Go Decomposition (GoDec. Experimental results demonstrated that the RPCA model was the most suitable for the small noise CT images whereas the GoDec model was the best for the large noisy CT images.

  3. CT image sequence restoration based on sparse and low-rank decomposition.

    Science.gov (United States)

    Gou, Shuiping; Wang, Yueyue; Wang, Zhilong; Peng, Yong; Zhang, Xiaopeng; Jiao, Licheng; Wu, Jianshe

    2013-01-01

    Blurry organ boundaries and soft tissue structures present a major challenge in biomedical image restoration. In this paper, we propose a low-rank decomposition-based method for computed tomography (CT) image sequence restoration, where the CT image sequence is decomposed into a sparse component and a low-rank component. A new point spread function of Weiner filter is employed to efficiently remove blur in the sparse component; a wiener filtering with the Gaussian PSF is used to recover the average image of the low-rank component. And then we get the recovered CT image sequence by combining the recovery low-rank image with all recovery sparse image sequence. Our method achieves restoration results with higher contrast, sharper organ boundaries and richer soft tissue structure information, compared with existing CT image restoration methods. The robustness of our method was assessed with numerical experiments using three different low-rank models: Robust Principle Component Analysis (RPCA), Linearized Alternating Direction Method with Adaptive Penalty (LADMAP) and Go Decomposition (GoDec). Experimental results demonstrated that the RPCA model was the most suitable for the small noise CT images whereas the GoDec model was the best for the large noisy CT images.

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

    DEFF Research Database (Denmark)

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

    2013-01-01

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

  5. Modeling current-voltage charateristics of proteorhodopsin and bacteriorhodopsin: towards an optoelectronics based on proteins.

    Science.gov (United States)

    Alfinito, Eleonora; Reggiani, Lino

    2016-10-18

    Current-voltage characteristics of metal-protein-metal structures made of proteorhodopsin and bacteriorhodopsin are modeled by using a percolation-like approach. Starting from the tertiary structure pertaining to the single protein, an analogous resistance network is created. Charge transfer inside the network is described as a sequential tunneling mechanism and the current is calculated for each value of the given voltage. The theory is validated with available experiments, in dark and light. The role of the tertiary structure of the single protein and of the mechanisms responsible for the photo-activity is discussed.

  6. Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

    Science.gov (United States)

    Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal

    2014-03-01

    Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

  7. Sensitivity based Assessment of Transient Voltage Sags caused by Rotor Swings

    DEFF Research Database (Denmark)

    Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Østergaard, Jacob

    2014-01-01

    The paper introduces an approach to investigate voltage sags, which are caused by large generator rotor swings following a transient disturbance. Therefore, the method exploits sensitivities derived from the algebraic network equations. These provide information on the impact of a generator...... on the voltage magnitude at a load bus and the effect of load variation on the generator’s power injection. It is shown that these sensitivities give valuable information to identify critical generator-load pairs and locations for applying preventive control measures....

  8. Modeling and Control of a DFIG-Based Wind Turbine During a Grid Voltage Drop

    Directory of Open Access Journals (Sweden)

    M. Shahabi

    2011-10-01

    Full Text Available Doubly-fed induction generators (DFIG are widely used in wind energy generation systems. During a grid voltage drop, performance is degraded with rotor over current deteriorating the fault-ride through (FRT capability of the DFIG wind-energy generation system. In this paper, a complete mathematical DFIG model is proposed. The rotor is considered fed by a voltage source converter whereas the stator is connected to the grid directly. Output power and electromagnetic torque are controlled using field-oriented control (FOC. Simulation results show the efficiency of the controller in exploiting the maximum power of wind.

  9. Evidence-based dentistry for planning restorative treatments: barriers and potential solutions.

    Science.gov (United States)

    Afrashtehfar, K I; Eimar, H; Yassine, R; Abi-Nader, S; Tamimi, F

    2017-11-01

    Evidence-based dentistry (EBD) can help provide the best treatment option for every patient, however, its implementation in restorative dentistry is very limited. This study aimed at assessing the barriers preventing the implementation of EBD among dental undergraduate and graduate students in Montreal, and explore possible solutions to overcome these barriers. A cross-sectional survey was conducted by means of a paper format self-administrated questionnaire distributed among dental students. The survey assessed the barriers and potential solutions for implementation of an evidence-based practice. Sixty-one students completed the questionnaire. Forty-one percent of respondents found evidence-based literature to be the most reliable source of information for restorative treatment planning, however, only 16% used it. They considered that finding reliable information was difficult and they sometimes encountered conflicting information when consulting different sources. Dental students had positive attitudes towards the need for better access to evidence-based literature to assist learning and decision making in restorative treatment planning and to improve treatment outcomes. Even for dentists trained in EBD, online searching takes too much time, and even though it can provide information of better quality than personal intuition, it might not be enough to identify the best available evidence. Even though dental students are aware of the importance of EBD in restorative dentistry they rarely apply the concept, mainly due to time constraints. For this reason, implementation of EBD would probably require faster access to evidence-based knowledge. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  10. Zirconium dioxide based dental restorations. Studies on clinical performance and fracture behaviour.

    Science.gov (United States)

    Larsson, Christel

    2011-01-01

    Loss of teeth can affect a person's appearance and functions such as eating and speaking. There is thus a need for prosthetic rehabilitation to improve quality of life. For many patients, a fixed dental restoration is preferred, and a common restoration is a porcelain-fused-to-metal bridge retained by teeth or implants. Metal-based restorations can potentially cause adverse reactions though, and this is cause for the search for alternative materials. All-ceramic materials are characterized by strong atomic bonds that make them reluctant to react with the environment, and thus unlikely to cause adverse reactions. All-ceramic materials have other attractive material properties and excellent aesthetic properties and have been successfully used in dentistry, mostly for smaller anterior restorations. Ceramics, however, do not withstand tensile forces as well as metals, and are susceptible to brittle fractures with the connector area being especially prone to fracture. More recently, a new type of ceramic material, based on zirconium dioxide, has been developed. Yttria-stabilized tetragonal zirconia polycrystal, Y-TZP, has a unique ability to resist crack propagation by being able to transform from one crystalline phase to another, and the resultant volume increase stops the crack and prevents it from propagating. This material has the potential to be used for larger restorations and in the molar area. Not enough information, however, is available on clinical follow-up of zirconia-based restorations, especially long-term, and information about all-ceramic restorations supported by implants is lacking. The aim of this thesis was to evaluate designs of zirconia-based restorations in relation to achieving increased fracture resistance and evaluate the clinical performance of implant-supported zirconia-based restorations. In paper I implant-supported all-ceramic fixed partial dentures of two different ceramic materials were compared; a zirconia-toughened alumina material

  11. Enhancing Output Voltage of Piezoelectric-Based Nanogenerators Using Zinc Oxide Material Codoped with Aluminum and Cobalt

    Science.gov (United States)

    Subagiyo, D.; Suyitno

    2017-11-01

    The cobalt and aluminum codoped into zinc oxide (ZnO) crystals are studied for enhancing the output voltage of piezoelectric-based nanogenerators (PENGs). The nanogenerators were simply fabricated from ZnO nanofibers (NFs) synthesized by electrospinning machine. The electrospinning processes were conducted at a flow rate of 4 μL/min and at various sintering temperature of 450, 500, 550, and 600°C. The results show that the highest output voltage of PENGs was obtained at a sintering temperature of 500°C, i.e. 127 mV. Therefore, PENGs fabricated from ZnO NFs codoped with aluminum and cobalt are challenging for the next generation of self-powered devices. The output voltage of PENGs at sintering temperatures of 450°C, 550°C, and 600°C are 75 mV, 105 mV, and 85 mV, respectively. The PENGs which fabricated from ZnO NFs was codoped with aluminum and cobalt will generate high output voltage, and are interesting candidates for exploiting in self-power devices.

  12. One-dimensional breakdown voltage model of SOI RESURF lateral power device based on lateral linearly graded approximation

    Science.gov (United States)

    Zhang, Jun; Guo, Yu-Feng; Xu, Yue; Lin, Hong; Yang, Hui; Hong, Yang; Yao, Jia-Fei

    2015-02-01

    A novel one-dimensional (1D) analytical model is proposed for quantifying the breakdown voltage of a reduced surface field (RESURF) lateral power device fabricated on silicon on an insulator (SOI) substrate. We assume that the charges in the depletion region contribute to the lateral PN junctions along the diagonal of the area shared by the lateral and vertical depletion regions. Based on the assumption, the lateral PN junction behaves as a linearly graded junction, thus resulting in a reduced surface electric field and high breakdown voltage. Using the proposed model, the breakdown voltage as a function of device parameters is investigated and compared with the numerical simulation by the TCAD tools. The analytical results are shown to be in fair agreement with the numerical results. Finally, a new RESURF criterion is derived which offers a useful scheme to optimize the structure parameters. This simple 1D model provides a clear physical insight into the RESURF effect and a new explanation on the improvement in breakdown voltage in an SOI RESURF device. Project supported by the National Natural Science Foundation of China (Grant No. 61076073) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20133223110003).

  13. A Practice-based Study on the Survival of Restored Endodontically Treated Teeth

    NARCIS (Netherlands)

    Skupien, J.A.; Opdam, N.; Winnen, R.; Bronkhorst, E.; Kreulen, C.; Pereira-Cenci, T.; Huysmans, M.C.D.N.J.M.

    2013-01-01

    INTRODUCTION: This retrospective study evaluated the survival of endodontically treated teeth (ETTs) and investigated factors influencing restoration and tooth survival. METHODS: Data from 795 ETTs were recorded, and success (restoration still intact) and survival (restoration intact or

  14. Power and Authority in the Student-Instructor Relationship in a Restorative Practices-Based Graduate Program

    Science.gov (United States)

    Bailie, John W., III

    2012-01-01

    This study examined power and authority in the student-instructor relationship in a restorative practices-based graduate program. This qualitative investigation utilized a narrative approach. Ten alumni of the International Institute for Restorative Practices master's degree programs were engaged in a one-time face-to-face interview and document…

  15. Super-resolution image restoration algorithms based on orthogonal discrete wavelet transform

    Science.gov (United States)

    Liu, Yang-yang; Jin, Wei-qi

    2005-02-01

    Several new super-resolution image restoration algorithms based on orthogonal discrete wavelet transform are proposed, by using orthogonal discrete wavelet transform and generalized cross validation ,and combining with Luck-Richardson super-resolution image restoration algorithm (LR) and Luck-Richardson algorithm based on Poisson-Markov model (MPML). Orthogonal discrete wavelet transform analyzed in both space and frequency domain has the capability of indicating local features of a signal, and concentrating the signal power to a few coefficients in wavelet transform domain. After an original image is "Symlets" orthogonal discrete wavelet transformed, an asymptotically optimal threshold is determined by minimizing generalized cross validation, and high frequency subbands in each decomposition level are denoised with soft threshold processes to converge respectively to those with maximum signal-noise-ratio, when the method is incorporated with existed super-resolution image algorithms, details of original image, especially of those with low signal-noise-ratio, could be well recovered. Single operation wavelet LR algorithm(SWLR),single operation wavelet MPML algorithm(SW-MPML) and MPML algorithm based on single operation and wavelet transform (MPML- SW) are some operative algorithms proposed based on the method. According to the processing results to simulating and practical images , because of the only one operation, under the guarantee of rapid and effective restoration processing, in comparison with LR and MPML, all the proposed algorithms could retain image details better, and be more suitable to low signal-noise-ratio images, They could also reduce operation time for up to hundreds times of iteratives, as well as, avoid the iterative operation of self-adaptive parameters in MPML, improve operating speed and precision. They are practical and instantaneous to some extent in the field of low signal-noise-ratio image restoration.

  16. Permanent Magnet Flux Online Estimation Based on Zero-Voltage Vector Injection Method

    DEFF Research Database (Denmark)

    Xie, Ge; Lu, Kaiyuan; Kumar, Dwivedi Sanjeet

    2015-01-01

    In this paper, a simple signal injection method is proposed for sensorless control of PMSM at low speed, which ideally requires one voltage vector only for position estimation. The proposed method is easy to implement resulting in low computation burden. No filters are needed for extracting the h...

  17. Initial position estimation method for permanent magnet synchronous motor based on improved pulse voltage injection

    DEFF Research Database (Denmark)

    Wang, Z.; Lu, K.; Ye, Y.

    2011-01-01

    According to saliency of permanent magnet synchronous motor (PMSM), the information of rotor position is implied in performance of stator inductances due to the magnetic saturation effect. Researches focused on the initial rotor position estimation of PMSM by injecting modulated pulse voltage...

  18. Complementary circuits based on solution processed low-voltage organic field-effect transistors

    NARCIS (Netherlands)

    Ball, James M.; Wöbkenberg, Paul H.; Kooistra, Floris B.; Hummelen, Jan C.; Leeuw, Dago M. de; Bradley, Donal D.C.; Anthopoulos, Thomas D.

    2009-01-01

    The field of organic electronics is advancing quickly towards ultra low-cost, low-end applications and is expected to provide the necessary technology required for flexible/printed electronics. Here we address the need for solution processed low-voltage complementary logic in order to reduce power

  19. Multi-Stage Optimization-Based Automatic Voltage Control Systems Considering Wind Power Forecasting Errors

    DEFF Research Database (Denmark)

    Qin, Nan; Bak, Claus Leth; Abildgaard, Hans

    2017-01-01

    cost and the generator reactive power output cost. The problem is formulated in a multi-stage optimal reactive power flow (MORPF) framework, solved by the nonlinear programming techniques via a rolling process. The voltage uncertainty caused by wind power forecasting errors is considered in the optimal...

  20. Auto-calibration of capacitive MEMS accelerometers based on pull-in voltage

    NARCIS (Netherlands)

    Rocha, L.A.; Dias, R.A.; Cretu, E.; Mol, L.; Wolffenbuttel, R.F.

    2011-01-01

    This paper describes an electro-mechanical auto-calibration technique for use in capacitive MEMS accelerometers. Auto-calibration is achieved using the combined information derived from an initial measurement of the resonance frequency and the measurement of the pull-in voltages during device

  1. Humidity Steady State Low Voltage Testing of MLCCs (Based on NESC Technical Assessment Report)

    Science.gov (United States)

    Sampson, Mike; Brusse, Jay; Teverovsky, Alexander

    2011-01-01

    Review of the low voltage reduced Insulation Resistance (IR) failure phenomenon in Multilayer ceramic capacitors (MLCCs)and NASA approaches to contend with this risk. 1. Analyze published materials on root cause mechanisms. 2. Investigate suitability of current test methods to assess MLCC lots for susceptibility. 3. Review current NASA parts selection and application guidelines in consideration of benefits vs. disadvantages.

  2. A Microprocessor-Based Control, Scheme for a PWM Voltage-Fed ...

    African Journals Online (AJOL)

    In this paper, the flexibility of programmed control logic is exploited in the close loop control of a PWM thyristor voltage fed inverter supplying an induction heating tank load. The microprocessor ... the microprocessor unit. Illustrative steady state and transient circuit of an experimental model of the induction heater are given.

  3. Coordinated Agent-Based Control for On-line Voltage Instability Prevention

    NARCIS (Netherlands)

    Baalbergen, J.F.

    2013-01-01

    Service interruptions have a significant impact on society and therefore the main objective of power system planning and operation is to ensure that they do not happen. Because voltage instability is one of the dynamic phenomena that may result in a system-wide blackout, this type of stability

  4. Induced over voltage test on transformers using enhanced Z-source inverter based circuit

    Science.gov (United States)

    Peter, Geno; Sherine, Anli

    2017-09-01

    The normal life of a transformer is well above 25 years. The economical operation of the distribution system has its roots in the equipments being used. The economy being such, that it is financially advantageous to replace transformers with more than 15 years of service in the second perennial market. Testing of transformer is required, as its an indication of the extent to which a transformer can comply with the customers specified requirements and the respective standards (IEC 60076-3). In this paper, induced over voltage testing on transformers using enhanced Z source inverter is discussed. Power electronic circuits are now essential for a whole array of industrial electronic products. The bulky motor generator set, which is used to generate the required frequency to conduct the induced over voltage testing of transformers is nowadays replaced by static frequency converter. First conventional Z-source inverter, and second an enhanced Z source inverter is being used to generate the required voltage and frequency to test the transformer for induced over voltage test, and its characteristics is analysed.

  5. Very low power, high voltage base for a Photo Multiplier Tube for the KM3NeT deep sea neutrino telescope

    CERN Document Server

    Timmer, P; Peek, H

    2010-01-01

    The described system is developed in the framework of a deep-sea submerged Very Large Volume neutrino Telescope where photons are detected by a large number of Photo Multiplier Tubes. These PMTs are placed in optical modules (OM). A basic Cockcroft-Walton (CW) voltage multiplier circuit design is used to generate multiple voltages to drive the dynodes of the photomultiplier tube. To achieve a long lifetime and a high reliability the dissipation in the OM must be kept to the minimum. The design is also constrained by size restrictions, load current, voltage range, and the maximum allowable ripple in the output voltage. A surface mount PMT-base PCB prototype is designed and successfully tested. The system draws less than 1.5 mA of supply current at a voltage of 3.3 V with outputs up to -1400 Vdc cathode voltage, a factor 10 less than the commercially available state of the art

  6. Fracture resistance of endodontically treated teeth restored with ceramic inlays and different base materials.

    Science.gov (United States)

    Saridag, Serkan; Sari, Tugrul; Ozyesil, Atilla Gokhan; Ari Aydinbelge, Hale

    2015-01-01

    This study evaluated the fracture resistance of endodontically treated teeth restored with different base materials and mesioocclusal-distal (MOD) ceramic inlays. Fifty mandibular molars were assigned into five groups (n=10 per group). Group1 (control) comprised intact molar teeth without any treatment. Teeth in other groups were subjected to root canal treatment and restored with MOD ceramic inlays on different base materials. In Group 2, base material was zinc phosphate cement; Group 3's was glass ionomer cement; Group 4's was composite resin, and Group 5's was composite resin reinforced with fiber. Finally, a continuous occlusal load was applied until fracture occurred. Mean fracture resistance of Group 1 (3,027 N) was significantly higher than the other groups (890, 1,070, 1,670, 1,226 N respectively). Fracture resistance of Group 4 was statistically comparable with Group 5 and significantly higher than Groups 2 and 3 (pmaterials under ceramic inlay restorations could affect the fracture resistance of endodontically treated teeth.

  7. Frequency Monitoring and Control during Power System Restoration Based on Wide Area Measurement System

    Directory of Open Access Journals (Sweden)

    Saber Nourizadeh

    2011-01-01

    Full Text Available Frequency control during power system restoration has not been strongly addressed. Operators are often concerned with the offline sizing of load and generation steps, but, nowadays, the introduction of Wide Area Measurement System (WAMS makes it possible to monitor the stability of power system online. The constraints of WAMS operation result in some changes in power system frequency control. This paper proposes a novel methodology for frequency control and monitoring during the early steps of power system restoration based on WAMS. Detailed load modeling is achieved based on the static load modeling approach. Power generators' modeling is also accomplished utilizing the single machine equivalent of the power system based on PMU measurements. Simulation results of the presented methodology on the 39 bus New England power system clearly show the effectiveness and applicability of the proposed method. The simulation results show that the presented approach has a completely acceptable precision and an outstanding speed with less than 0.05% error. The outstanding speed of the presented approach along with the result precision will result in a great promotion in power system restoration methodologies.

  8. Compound control method of neutral point voltage of three level NPC inverter based on the vector method of virtual space and hysteresis control

    Science.gov (United States)

    Yang, Fengping; Xiao, Fangfei

    2017-03-01

    Current control methods include hardware control and software control corresponding to the inherent unbalance problem of neutral point voltage in three level NPC inverter. The hardware control is rarely used due to its high cost. In this paper, a new compound control method has been presented based on the vector method of virtual space and traditional hysteresis control of neutral point voltage, which can make up the shortcoming of the virtual control without the feedback control system of neutral point voltage and the blind area of hysteresis control and control the deviation and wave of neutral point voltage. The accuracy of this method has been demonstrated by simulation.

  9. A Comparative Analysis between GaN-Based Current and Voltage Mode Class-D and E PAs for Communications

    Science.gov (United States)

    2017-03-01

    A Comparative Analysis between GaN-Based Current and Voltage Mode Class-D and E PAs for Communications Shishir Shukla and Jennifer Kitchen...programmability and efficiency. Radar and imaging systems that use constant envelope waveforms may exploit the advantages of highly nonlinear, or switched...709–717, Dec 2005. 7. T. Suetsugu and M. K. Kazimierczuk, “Off-Nominal Operation of Class-E Amplifier at Any Duty Ratio ,” IEEE Transactions on

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

    Science.gov (United States)

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

    2017-12-01

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

  11. Image degradation characteristics and restoration based on regularization for diffractive imaging

    Science.gov (United States)

    Zhi, Xiyang; Jiang, Shikai; Zhang, Wei; Wang, Dawei; Li, Yun

    2017-11-01

    The diffractive membrane optical imaging system is an important development trend of ultra large aperture and lightweight space camera. However, related investigations on physics-based diffractive imaging degradation characteristics and corresponding image restoration methods are less studied. In this paper, the model of image quality degradation for the diffraction imaging system is first deduced mathematically based on diffraction theory and then the degradation characteristics are analyzed. On this basis, a novel regularization model of image restoration that contains multiple prior constraints is established. After that, the solving approach of the equation with the multi-norm coexistence and multi-regularization parameters (prior's parameters) is presented. Subsequently, the space-variant PSF image restoration method for large aperture diffractive imaging system is proposed combined with block idea of isoplanatic region. Experimentally, the proposed algorithm demonstrates its capacity to achieve multi-objective improvement including MTF enhancing, dispersion correcting, noise and artifact suppressing as well as image's detail preserving, and produce satisfactory visual quality. This can provide scientific basis for applications and possesses potential application prospects on future space applications of diffractive membrane imaging technology.

  12. Flood Hydrograph Restoration in Increasingly-urbanized Area Based on Low Elevation Greenbelt

    Science.gov (United States)

    GAO, Cheng; Yang, Tao

    2015-04-01

    In increasingly urbanized area, water surface ratio descends and storage capacity of water decreases rapidly associated with lakes, branches, wetlands and floodplains buried. In addition, land surface impermeability enlarges runoff coefficients and runoff velocity. Urban flood, with higher peak discharge, larger volume and shorter concentration time, brings higher risk than rural area. Flood hydrograph restoration is to restore the flood hydrograph after urbanization by specific strategies, by compensating water surface ratio (WSR) and pervious surface proportion (PSP) for peak attenuation, volume reduction and concentration time increase. This paper presents the equivalent effect of low elevation greenbelt- a type of low impact development practices and WSR, PSP by the model SWMM, based on which, the corresponding compensative water surface ratio (CWSR) and compensative pervious surface proportion (CPSP) were obtained according to the equal peak discharge, volume of flood and concentration time- the three parameters determining the flood hydrograph. Then a relationship was found out between the ratio of low elevation greenbelt and WSR, PSP. Finally, the just ratio of low elevation greenbelt and the amount of rainwater resource utilization can be got by comparison of flood hydrograph with the one before urbanization for the restoration based on the three parameters to reduce effect of urbanization on flood hydrograph.

  13. Fast Restoration Based on Alternative Wavelength Paths in a Wide Area Optical IP Network

    Science.gov (United States)

    Matera, Francesco; Rea, Luca; Venezia, Matteo; Capanna, Lorenzo; Del Prete, Giuseppe

    In this article we describe an experimental investigation of IP network restoration based on wavelength recovery. We propose a procedure for metro and wide area gigabit Ethernet networks that allows us to route the wavelength in case of link failure to another existing link by exploiting wavelength division multiplexing in the fiber. Such a procedure is obtained by means of an optical switch that is managed by a loss-of-light signal that is generated by a router in case of link failure. Such a method has been tested in an IP network consisting of three core routers with optical gigabit Ethernet interfaces connected by means of 50-km-long single-mode fibers between Rome and Pomezia. Compared with other conventional restoration techniques, such as OSPF and MPLS, our method -in very fast (20 ms) and is compatible with real-time TV services and low-cost chips.

  14. Image restoration via patch orientation-based low-rank matrix approximation and nonlocal means

    Science.gov (United States)

    Zhang, Di; He, Jiazhong; Du, Minghui

    2016-03-01

    Low-rank matrix approximation and nonlocal means (NLM) are two popular techniques for image restoration. Although the basic principle for applying these two techniques is the same, i.e., similar image patches are abundant in the image, previously published related algorithms use either low-rank matrix approximation or NLM because they manipulate the information of similar patches in different ways. We propose a method for image restoration by jointly using low-rank matrix approximation and NLM in a unified minimization framework. To improve the accuracy of determining similar patches, we also propose a patch similarity measurement based on curvelet transform. Extensive experiments on image deblurring and compressive sensing image recovery validate that the proposed method achieves better results than many state-of-the-art algorithms in terms of both quantitative measures and visual perception.

  15. Containment and Consensus-based Distributed Coordination Control to Achieve Bounded Voltage and Precise Reactive Power Sharing in Islanded AC Microgrids

    DEFF Research Database (Denmark)

    Han, Renke; Meng, Lexuan; Ferrari-Trecate, Giancarlo

    2017-01-01

    for coordinated control design. Furthermore, a containment and consensus-based distributed coordination controller is proposed, by which the bus voltage magnitudes can be bounded within a reasonable range, instead of only controlling average voltage value. Further, the accurate reactive power sharing between...

  16. Decentralized Load Sharing in a Low-Voltage Direct Current Microgrid With an Adaptive Droop Approach Based on a Superimposed Frequency

    DEFF Research Database (Denmark)

    Peyghami, Saeed; Mokhtari, Hossein; Blaabjerg, Frede

    2017-01-01

    Conventional droop methods for load sharing control in low-voltage direct current microgrids suffer from poor power sharing and voltage regulation, especially in the case when operating many dc sources with long feeders. Hence, the communication-based approaches are employed to improve the load...

  17. Effect of using different base materials on microleakage of class V restorations

    Directory of Open Access Journals (Sweden)

    İhsan Yıkılgan

    2017-01-01

    Full Text Available Objective: The aim of this in vitro study was to evaluate and compare the effect of using different base materials on microleakage of class V restorations. Materials and Method: In this study 60 extracted non-cavitated human molar teeth were used. Class V cavities were prepared on the buccal surfaces in 4 mm mesio-distal, 3 mm gingivo-occlusal width and 3 mm depth. The teeth were randomly divided into five groups: Group 1: resin-modified calcium silicate material (TheraCal LC, Group 2: self-adhesive flowable composite resin (Fusio Liquid Dentin, Group 3: flowable composite resin liner (Tetric N Flow, Group 4: resin-modified glass ionomer liner (Ketac N100, Group 5: control group. Materials in the experimental groups were placed in 1 mm thickness as liner. Then, a nanohybrid composite resin (Grandio was placed and restorations were completed. In the control group, no base material was applied. After finishing and polishing procedures, thermocycling was performed 5000 times between 5-55 °C. Microleakage of restorations was evaluated by using dye penetration method (basic fuchsin. Results were analyzed by Kruskal Wallis with Bonferroni correction and Mann-Whitney U tests. Results: Regarding occlusal microleakage, no statistically significant difference was found between the groups (p=0.267; however significant difference was found between the gingival microleakage scores (p=0.004. Compared to Fusio Liquid Dentin and control groups, significantly less dye penetration was found in Theracal LC, Tetric N-Flow and Ketac N-100 groups (p0.01. Conclusion: Within the limitation of this study, the conclusion was that the use of a liner (except Fusio Liquid Dentin under composite resin in a class V cavity reduced the microleakage of the restoration.

  18. Spatially inhomogeneous photoluminescence-voltage hysteresis in planar heterojunction perovskite-based solar cells

    Science.gov (United States)

    Xu, Zhihua; Edgeton, Anthony; Costello, Sydney

    2017-11-01

    Spatially resolved photoluminescence (PL) of methylammonium lead iodide (MAPbI3) films in planar heterojunction solar cells is probed by time-resolved confocal microscopy to study the interface effect on PL intensity-voltage (PL-V) hysteresis. Negligible PL-V hysteresis is observed at the interfacial area, while significant hysteresis is observed in the bulk film. PL lifetime imaging of the perovskite device reveals inhomogeneous charge extraction due to variation of the interfacial contact quality. Poor interfacial contact leads to more severe PL-V hysteresis in the bulk perovskite film. The PL-V characteristics also suggest that voltage-driven ion migration may lead to redistribution of charge traps, and consequently affect the nonradiative charge recombination and the PL intensity in MAPbI3 films.

  19. Design of a high DC voltage generator and D-T fuser based on particle accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Wagner L.; Campos, Tarcisio P.R., E-mail: wagnerleite@ufmg.b, E-mail: campos@nuclear.ufmg.b [Universidade Federal de Minas Gerais (DEN/ UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Nuclear

    2011-07-01

    This paper approaches a design and simulation of a high voltage Cockcroft Walton multiplier and a compact size deuteron accelerator addressed in neutron generation by d-t fusion. We proposed a circuit arrangement, which was led to simulations. The particle accelerator was computer-generated providing particle transport and electric potential analysis. As results, the simulated voltage multiplier achieved 119 kV, and the accelerator presented a deuteron beam current up to 15 mA, achieving energies in order to 100 keV. In conclusion, the simulation motivates experimental essays in order to investigate the viability of a deuteron accelerator powered by a Cockcroft-Walton source. Such d-t fusor shall produce an interesting ion beam profile, reaching energy values near the d-t fusion cross section peak. (author)

  20. Voltage Harmonics Monitoring in a Microgrid Based on Advanced Metering Infrastructure (AMI)

    DEFF Research Database (Denmark)

    Firoozabadi, Mehdi Savaghebi; Guan, Yajuan; Quintero, Juan Carlos Vasquez

    2015-01-01

    Smart meters are the main part of Advanced Metering Infrastructure (AMI) and are usually able to provide detailed information on customers’ energy consumptions, voltage variations and interruptions. In addition, these meters are potentially able to provide more information about power quality (PQ......) disturbances. This paper will address the monitoring of voltage harmonics utilizing the features of smart meters and AMI system. To do this, the first step is to select proper indices to quantify the distortion. An important point which should be considered in this regard is the limited processing power...... of smart meters in comparison with PQ Analyzers (PQAs). Furthermore, the indices are categorized as site and system indices. The site indices measure the distortion at one metering section while the system indices provide a PQ view in an area encompassing multiple meters. In addition, the smart metering...

  1. A practical fast acting control scheme for fuzzy logic-based voltage stabilization control

    Directory of Open Access Journals (Sweden)

    El-Kholy E.E.

    2005-01-01

    Full Text Available This paper presents a simplified control model for stabilizing a load voltage using a switched reactor in parallel with a fixed capacitor of static VAR compensator. Two IGBT’s are used to control the reactance of the switched reactor. A uniform pulse width modulation is used for controlling the two switches. The compensator has a simple control circuit and structure. A complete modeling and numerical simulation for the proposed systems are presented. A high speed Digital Signal Processor is used for implementing proportional integral (PI and fuzzy load voltage controllers. Experimental results indicate the superiority of fuzzy logic control over the conventional proportional-integral control method. Simulation results are reported and proved to be in good agreement with the relevant experimental results.

  2. A Practical Fast Acting Control Scheme For Fuzzy Logic-Based Voltage Stabilization Control

    Directory of Open Access Journals (Sweden)

    E. E. EL-Kholy

    2005-03-01

    Full Text Available This paper presents a simplified control model for stabilizing a load voltage using a switched reactor in parallel with a fixed capacitor of static VAR compensator. Two IGBT’s are used to control the reactance of the switched reactor. A uniform pulse width modulation is used for controlling the two switches. The compensator has a simple control circuit and structure. A complete modeling and numerical simulation for the proposed systems is presented. A high speed Digital Signal Processor is used for implementing proportional-integral (PI and fuzzy load voltage controllers. Experimental results indicate the superiority of fuzzy logic control over the conventional proportional-integral control method. Simulation results are reported and proved to be in good agreement with the relevant experimental results.

  3. Dual-frequency low-voltage subterahertz radial clinotron based on fan-shaped splitter

    Science.gov (United States)

    Chen, Zaigao; Wang, Jianguo; Wang, Yue

    2017-05-01

    To further improve the output power and tuning bandwidth of compact low-voltage subterahertz vacuum electron devices, a novel dual-frequency low-voltage subterahertz radial clinotron oscillator, in which two fan-shaped radial electron beams transmit inward along the axial direction and interact with two fan-shaped slow wave structures (SWSs) machined on the azimuthally symmetric planar plate individually, is studied in this paper. Compared to the clinotron where the planar SWS composed of the rectangular grooves is adopted, the dispersion curve of proposed fan-shaped radial SWSs is independent of radius and azimuthal coordinates. The particle-in-cell simulation results indicate that the designed clinotron can simultaneously produce the electromagnetic waves at 0.305 THz and 0.34 THz, the corresponding output powers are 9.1 W and 24 W, and the tuning range of bandwidth can be significantly broadened.

  4. Low Noise Bias Current/Voltage References Based on Floating-Gate MOS Transistors

    DEFF Research Database (Denmark)

    Igor, Mucha

    1997-01-01

    The exploitation of floating-gate MOS transistors as reference current and voltage sources is investigated. Test structures of common source and common drain floating-gate devices have been implemented in a commercially available 0.8 micron double-poly CMOS process. The measurements performed pro...... promise a good maintenance of the operating point of the floating-gate devices. Examples of utilizing of such bias sources in low-noise sensor preamplifiers are discussed....

  5. Dynamic data transmission technology for expendable current profiler based on low-voltage differential signaling

    OpenAIRE

    Li, S.; Zhang, Q; Zhao, X.; S. Liu; Yuan, Z.; X. Zhang

    2017-01-01

    A dynamic data transmission technology for expendable current profilers (XCPs) is proposed in this paper. Two parallel varnished wires are employed as the data transmission medium. By testing the transmission properties of the varnished wires, a baseband transmission system is studied and designed. Modified low-voltage differential signaling (LVDS) is adopted as the physical layer for data transmission. The data transmission protocol is modified and optimized in accordance with...

  6. Research of Measurement Circuits for High Voltage Current Transformer Based on Rogowski Coils

    OpenAIRE

    Yan Bing; Wang Yutian; Li Hui; Wang Huixin; Chen Yiqiang

    2014-01-01

    The electronic current transformer plays an irreplaceable position in the field of relay protection and current measurement of the power system. Rogowski coils are used as sensor parts, and in order to improve the measurement accuracy and reliability, the circuits at the high voltage system are introduced and improved in this paper, including the analog integral element, the filtering circuit and the phase shift circuit. Simulations results proved the reliability and accuracy of the improved ...

  7. Research of Measurement Circuits for High Voltage Current Transformer Based on Rogowski Coils

    Directory of Open Access Journals (Sweden)

    Yan Bing

    2014-02-01

    Full Text Available The electronic current transformer plays an irreplaceable position in the field of relay protection and current measurement of the power system. Rogowski coils are used as sensor parts, and in order to improve the measurement accuracy and reliability, the circuits at the high voltage system are introduced and improved in this paper, including the analog integral element, the filtering circuit and the phase shift circuit. Simulations results proved the reliability and accuracy of the improved circuits.

  8. Capacitance Estimation Algorithm based on DC-Link Voltage Harmonics Using ANN in Three-Phase Motor Drive Systems

    DEFF Research Database (Denmark)

    Soliman, Hammam Abdelaal Hammam; Davari, Pooya; Wang, Huai

    2017-01-01

    to industry. In this digest, a condition monitoring methodology that estimates the capacitance value of the dc-link capacitor in a three phase Front-End diode bridge motor drive is proposed. The proposed software methodology is based on Artificial Neural Network (ANN) algorithm. The harmonics of the dc......-link voltage are used as training data to the Artificial Neural Network. Fast Fourier Transform (FFT) of the dc-link voltage is analysed in order to study the impact of capacitance variation on the harmonics order. Laboratory experiments are conducted to validate the proposed methodology and the error analysis......In modern design of power electronic converters, reliability of dc-link capacitors is one of the critical considered aspects. The industrial field have been attracted to the monitoring of their health condition and the estimation of their ageing process status. However, the existing condition...

  9. Temperature and bias-voltage dependence of atomic-layer-deposited HfO{sub 2}-based magnetic tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Fabretti, Savio, E-mail: fabretti@physik.uni-bielefeld.de [Thin Films and Physics of Nanostructures, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld (Germany); Zierold, Robert; Nielsch, Kornelius [Institute of Applied Physics, Universität Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany); Voigt, Carmen; Ronning, Carsten [Institute for Solid State Physics, Friedrich-Schiller-University Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Peretzki, Patrick; Seibt, Michael [4. Physikalisches Institut, Georg-August University Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany); Thomas, Andy [Thin Films and Physics of Nanostructures, Universitaetsstrasse 25, 33615 Bielefeld, Germany, and Institut für Physik, Johannes Gutenberg Universität Mainz, Staudingerweg 9, 55128 Mainz (Germany)

    2014-09-29

    Magnetic tunnel junctions with HfO{sub 2} tunnel barriers were prepared through a combination of magnetron sputtering and atomic layer deposition. We investigated the tunneling transport behavior, including the tunnel magnetoresistance ratio and the current-voltage characteristics between room temperature and 2 K. Here, we achieved a tunneling magneto resistance ratio of 10.3% at room temperature and 19.3% at 2 K. Furthermore, we studied the bias-voltage and temperature dependencies and compared the results with those of commonly used alumina- and magnesia-based magnetic tunnel junctions. We observed a polycrystalline/amorphous electrode-barrier system via high-resolution transmission electron microscopy.

  10. Topology and Control of Transformerless High Voltage Grid-connected PV System Based on Cascade Step-up Structure

    DEFF Research Database (Denmark)

    Yang, Zilong; Wang, Zhe; Zhang, Ying

    2017-01-01

    In order to realize maximum power output of photovoltaics (PV), reduce line losses, and decrease abandoned solar energy during weak irradiance , a new medium voltage gridconnected PV system structure based on cascaded converters was proposed in this paper. A transformerless cascade step......-up structure, instead of applying line-frequency step-up transformer, is proposed to connect PV directly to the 10 kV medium voltage grid. This series-connected step-up PV system integrates with multiple functions, including separated maximum power point tracking (MPPT), centralized energy storage, power...... quality regulation. Its inherent excellent features makes it not only adapt to different geographical and environmental installing conditions, but also to improve converter efficiency and flexibility. This paper focuses on the analyses of system structure design, control principle and strategy...

  11. Low-threshold voltage ultraviolet light-emitting diodes based on (Al,Ga)N metal–insulator–semiconductor structures

    Science.gov (United States)

    Liang, Yu-Han; Towe, Elias

    2017-12-01

    Al-rich III–nitride-based deep-ultraviolet (UV) (275–320 nm) light-emitting diodes are plagued with a low emission efficiency and high turn-on voltages. We report Al-rich (Al,Ga)N metal–insulator–semiconductor UV light-emitting Schottky diodes with low turn-on voltages of insulator and an n-type Al0.58Ga0.42N film as the semiconductor. To improve the efficiency, we inserted a GaN quantum-well structure between the AlN insulator and the n-type Al x Ga1‑ x N semiconductor. The benefits of the quantum-well structure include the potential to tune the emission wavelength and the capability to confine carriers for more efficient radiative recombination.

  12. Low-voltage organic thin-film transistors based on solution-processed hybrid dielectrics: theoretical and experimental studies

    Science.gov (United States)

    Ke, Qiutan; Wu, Qian; Liang, Lijuan; Pei, Yanli; Lu, Xubing; Li, Minmin; Huang, Kairong; Liu, Xuying; Liu, Chuan

    2017-10-01

    In organic thin-film transistors (OTFTs), using high-k dielectrics could increase the accumulated carrier numbers at low operation voltage (i.e. the bulk effect), but may induce extra dipolar disorders to affect the electronic states in organic semiconductors (i.e. the interfacial effect). The two effects are considered together to model charge transport in OTFTs and to give quantitative calculations of the impacts from using high-k dielectrics or hybrid dielectrics, especially the relations between mobility and Fermi-energy, carrier concentrations, or gate-voltage. In experimental studies, zirconium oxide (ZrO2) and yttrium oxide (Y2O3) are fabricated by solution process for high-k dielectrics. The oxide insulating films are modified by low-k polymer layers and the resulting OTFTs show low operation voltage and high performance in ambient test. The highest mobility reaches 2.38 cm2 V-1 s-1 for ZrO2 based OTFT and 3.56 cm2 V-1 s-1 for Y2O3 based OTFT, and the on/off ratio is 1.4 × 104 for ZrO2 devices and 5.4 × 104 for Y2O3 devices. In general, the trends of experimentally measured mobility are consistent with the theoretical calculations, showing the high-k/low-k hybrid dielectrics mainly improve the carrier mobility in the regime of low carrier density.

  13. A multi-mode operation control strategy for flexible microgrid based on sliding-mode direct voltage and hierarchical controls.

    Science.gov (United States)

    Zhang, Qinjin; Liu, Yancheng; Zhao, Youtao; Wang, Ning

    2016-03-01

    Multi-mode operation and transient stability are two problems that significantly affect flexible microgrid (MG). This paper proposes a multi-mode operation control strategy for flexible MG based on a three-layer hierarchical structure. The proposed structure is composed of autonomous, cooperative, and scheduling controllers. Autonomous controller is utilized to control the performance of the single micro-source inverter. An adaptive sliding-mode direct voltage loop and an improved droop power loop based on virtual negative impedance are presented respectively to enhance the system disturbance-rejection performance and the power sharing accuracy. Cooperative controller, which is composed of secondary voltage/frequency control and phase synchronization control, is designed to eliminate the voltage/frequency deviations produced by the autonomous controller and prepare for grid connection. Scheduling controller manages the power flow between the MG and the grid. The MG with the improved hierarchical control scheme can achieve seamless transitions from islanded to grid-connected mode and have a good transient performance. In addition the presented work can also optimize the power quality issues and improve the load power sharing accuracy between parallel VSIs. Finally, the transient performance and effectiveness of the proposed control scheme are evaluated by theoretical analysis and simulation results. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

  14. Implementation of Dynamic Voltage Restorer for Mitigation of Voltage Sag

    National Research Council Canada - National Science Library

    K.Vinod Kumar

    2013-01-01

    Power quality is one of major concerns in the present. It has become important, especially with the introduction of sophisticated devices, whose performance is very sensitive to the quality of power supply...

  15. A prospective randomized clinical trial of one bis-GMA-based and two ormocer-based composite restorative systems in class II cavities: five-year results

    NARCIS (Netherlands)

    Bottenberg, P.; Jacquet, W.; Alaerts, M.; Keulemans, F.

    2009-01-01

    Objectives: Ormocer composites, consisting of a silicon-based polymer, have been developed recently as a tooth-colored restorative material. The purpose of this prospective randomized clinical trial was to evaluate the performance of two small-particle hybrid ormocer-based restorative systems (AD,

  16. Cuspal Deflection in Premolar Teeth Restored with Bulk-Fill Resin-Based Composite Materials.

    Science.gov (United States)

    Elsharkasi, M M; Platt, J A; Cook, N B; Yassen, G H; Matis, B A

    The present study investigated the effect of three high-viscosity bulk-fill resin-based composite materials on cuspal deflection in natural teeth. Thirty-two sound maxillary premolar teeth with large slot mesio-occlusal-distal cavities were distributed into four groups (n=8). Three groups were restored with bulk-fill resin composite materials (Tetric EvoCeram Bulk Fill, Ivoclar Vivadent, Schaan, Liechtenstein; x-tra fil, VOCO, Cuxhaven, Germany; and SonicFill, Kerr, Orange, CA, USA) in a single 4-mm increment. The conventional composite group, Filtek Z100 (3M ESPE, St Paul, MN, USA), was used to restore the cavities in 2-mm increments. Cusp deflection was recorded postirradiation using a Nikon measurescope UM-2 (Nikon, Tokyo, Japan) by measuring the changes in the bucco-palatal widths of the teeth at five minutes, 24 hours, and 48 hours after completion of the restorations. Cuspal deflection was significantly higher in the conventional composite than in the Tetric EvoCeram Bulk Fill ( p=0.0031), x-tra fil ( p=0.0029), and SonicFill Bulk ( p=0.0002) groups. There were no significant differences in cuspal deflection among the three bulk-fill materials (all pcomposites exhibited cuspal deflection values that were smaller than those associated with a conventional incrementally placed resin composite.

  17. Functional tooth restoration by allogeneic mesenchymal stem cell-based bio-root regeneration in swine.

    Science.gov (United States)

    Wei, Fulan; Song, Tieli; Ding, Gang; Xu, Junji; Liu, Yi; Liu, Dayong; Fan, Zhipeng; Zhang, Chunmei; Shi, Songtao; Wang, Songlin

    2013-06-15

    Our previous proof-of-concept study showed the feasibility of regenerating the dental stem cell-based bioengineered tooth root (bio-root) structure in a large animal model. Here, we used allogeneic dental mesenchymal stem cells to regenerate bio-root, and then installed a crown on the bio-root to restore tooth function. A root shape hydroxyapatite tricalcium phosphate scaffold containing dental pulp stem cells was covered by a Vc-induced periodontal ligament stem cell sheet and implanted into a newly generated jaw bone implant socket. Six months after implantation, a prefabricated porcelain crown was cemented to the implant and subjected to tooth function. Clinical, radiological, histological, ultrastructural, systemic immunological evaluations and mechanical properties were analyzed for dynamic changes in the bio-root structure. The regenerated bio-root exhibited characteristics of a normal tooth after 6 months of use, including dentinal tubule-like and functional periodontal ligament-like structures. No immunological response to the bio-roots was observed. We developed a standard stem cell procedure for bio-root regeneration to restore adult tooth function. This study is the first to successfully regenerate a functional bio-root structure for artificial crown restoration by using allogeneic dental stem cells and Vc-induced cell sheet, and assess the recipient immune response in a preclinical model.

  18. Decentralized Load Sharing in a Low-Voltage Direct Current Microgrid With an Adaptive Droop Approach Based on a Superimposed Frequency

    DEFF Research Database (Denmark)

    Peyghami, Saeed; Mokhtari, Hossein; Blaabjerg, Frede

    2017-01-01

    sharing accuracy and voltage regulation. To avoid using such an infrastructure and the corresponding effects on the reliability and stability, an adaptive droop controller based on a superimposed frequency is proposed in this paper. Load sharing accuracy is improved by adapting the droop gains utilizing......Conventional droop methods for load sharing control in low-voltage direct current microgrids suffer from poor power sharing and voltage regulation, especially in the case when operating many dc sources with long feeders. Hence, the communication-based approaches are employed to improve the load...... an introduced ac power. The secondary controller locally estimates and compensates the voltage drop due to the droop controller. The proposed power sharing approach can properly control the load sharing and voltage regulation without utilizing any extra communication system. The effectiveness of the proposed...

  19. Voltage Controlled Dynamic Demand Response

    DEFF Research Database (Denmark)

    Bhattarai, Bishnu Prasad; Bak-Jensen, Birgitte; Mahat, Pukar

    2013-01-01

    central or dispersed generations might not be sufficient for future scenario. One of the effective methods to cope with this scenario is to enable demand response. This paper proposes a dynamic voltage regulation based demand response technique to be applied in low voltage (LV) distribution feeders....... An adaptive dynamic model has been developed to determine composite voltage dependency of an aggregated load on feeder level. Following the demand dispatch or control signal, optimum voltage setting at the LV substation is determined based on the voltage dependency of the load. Furthermore, a new technique...... has been proposed to estimate the voltage at consumer point of connection (POC) to ensure operation within voltage limits. Finally, the effectiveness of the proposed method is analyzed comprehensively with reference to three different scenarios on a low voltage (LV) feeder (Borup feeder) owned...

  20. Reasons for placement of restorations on previously unrestored tooth surfaces by dentists in The Dental Practice-Based Research Network

    DEFF Research Database (Denmark)

    Nascimento, Marcelle M; Gordan, Valeria V; Qvist, Vibeke

    2010-01-01

    The authors conducted a study to identify and quantify the reasons used by dentists in The Dental Practice-Based Research Network (DPBRN) for placing restorations on unrestored permanent tooth surfaces and the dental materials they used in doing so.......The authors conducted a study to identify and quantify the reasons used by dentists in The Dental Practice-Based Research Network (DPBRN) for placing restorations on unrestored permanent tooth surfaces and the dental materials they used in doing so....

  1. Community based ecological restoration of peatland in Central Mongolia for climate change mitigation and adaptation

    Science.gov (United States)

    Minayeva, Tatiana; Chultem, Dugarjav; Grootjans, Ab; Yamkhin, Jambaljav; Sirin, Andrey; Suvorov, Gennady; Batdorj, Oyunbileg; Tsamba, Batdorj

    2017-04-01

    understanding of functional particularities of peatland ecosystem and restoration efforts are not effective. Following the baseline study the concept for ecosystem restoration project had been developed. The approach was to merge community based solution with scientific approaches. Restoration in subhumid conditions should avoid creation of open water surfaces, like channels or reservoirs, and deal with integrative ecosystem management. The restoration concept involved fencing of springs, preventing erosion and enhancing water accumulation in soil by cascades of small dams and other small scale ecological solutions. At the same time to meet the needs of local herders, it was decided to repair the dam, constructed by herders, even if it has little value for peatland restoration. The engineering design is now ready and will be implemented next months. The last part of the pilot is monitoring. The parameters determined in the baseline study are included in monitoring program to help to evaluate: carbon sequestration rate, GHG emission reduction, water retention, soil humidity, pasture productivity, social integrity and impact on livelihoods.

  2. A fuzzy-based approach for open-transistor fault diagnosis in voltage-source inverter induction motor drives

    Science.gov (United States)

    Zhang, Jianghan; Luo, Hui; Zhao, Jin; Wu, Feng

    2015-02-01

    This paper develops a novel method for the detection and isolation of open-transistor faults in voltage-source inverters feeding induction motors. Based on analyzing the load currents trajectories after Concordia transformation, six diagnostic signals each of which indicates a certain switch are extracted and a fuzzy rule base is designed to perform fuzzy reasoning in order to detect and isolate 21 fault modes including single- and double-transistor faults. In addition, the fuzzy rules are rearranged and each of them is set to a reasonable value representing the fault modes. The simulation and experiment are carried out to demonstrate the effectiveness of the proposed fuzzy approach.

  3. Cyanoethyl cellulose-based nanocomposite dielectric for low-voltage, solution-processed organic field-effect transistors (OFETs)

    Science.gov (United States)

    Faraji, Sheida; Danesh, Ehsan; Tate, Daniel J.; Turner, Michael L.; Majewski, Leszek A.

    2016-05-01

    Low voltage organic field-effect transistors (OFETs) using solution-processed cyanoethyl cellulose (CEC) and CEC-based nanocomposites as the gate dielectric are demonstrated. Barium strontium titanate (BST) nanoparticles are homogeneously dispersed in CEC to form the high-k (18.0  ±  0.2 at 1 kHz) nanocomposite insulator layer. The optimised p-channel DPPTTT OFETs with BST-CEC nanocomposite as the gate dielectric operate with minimal hysteresis, display field-effect mobilities in excess of 1 cm2 V-1 s-1 at 3 V, possess low subthreshold swings (132  ±  8 mV dec-1), and have on/off ratios greater than 103. Addition of a 40-50 nm layer of cross-linked poly(vinyl phenol) (PVP) on the surface of the nanocomposite layer significantly decreases the gate leakage current (<10-7 A cm-2 at  ±3 V) and the threshold voltage (<  -0.7 V) enabling operation of the OFETs at 1.5 V. The presented bilayer BST-CEC/PVP dielectrics are a promising alternative for the fabrication of low voltage, solution-processed OFETs that are suitable for use in low power, portable electronics.

  4. An AT89C52 Microcontroller Based High Resolution PWM Controller for 3-Phase Voltage Source Inverters

    Directory of Open Access Journals (Sweden)

    K. M. Rahman and S. J. M. Idrus

    2012-10-01

    Full Text Available A novel technique for generating real time high resolution pulse width modulated patterns for a three phase voltage source inverter is presented in this paper. An AT89C52 microcontroller computes the PWM pulse widths on carrier cycle basis based on the input frequency.  The microcontroller send the pulse width information for the three phases to a memory minimized ROM lookup table, which is scanned by a binary counter to generate the real time PWM patterns. The on board timer of AT89C52 is utilized to generate programmed clock for the scanning binary counter. The overall design is hardware minimized and compact that makes it feasible for low cost high performance ac drive applications.  The proposed PWM controller supports variable frequency variable voltage operation for wide range and hence is ideally suited for industrial drives requiring wide speed variations.  Keywords: Pulse width modulation, Microcontroller application, Voltage source inverter, variable speed ac drives.

  5. A new type of accelerator power supply based on voltage-type space vector PWM rectification technology

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Fengjun, E-mail: wufengjun@impcas.ac.cn [Institute of Modern Physics, CAS, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Gao, Daqing; Shi, Chunfeng; Huang, Yuzhen [Institute of Modern Physics, CAS, Lanzhou 730000 (China); Cui, Yuan [Institute of Modern Physics, CAS, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Yan, Hongbin [Institute of Modern Physics, CAS, Lanzhou 730000 (China); Zhang, Huajian [Institute of Modern Physics, CAS, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Bin [University of Chinese Academy of Sciences, Beijing 100049 (China); Li, Xiaohui [Institute of Modern Physics, CAS, Lanzhou 730000 (China)

    2016-08-01

    To solve the problems such as low input power factor, a large number of AC current harmonics and instable DC bus voltage due to the diode or thyristor rectifier used in an accelerator power supply, particularly in the Heavy Ion Research Facility in Lanzhou-Cooler Storage Ring (HIRFL-CSR), we designed and built up a new type of accelerator power supply prototype base on voltage-type space vector PWM (SVPWM) rectification technology. All the control strategies are developed in TMS320C28346, which is a digital signal processor from TI. The experimental results indicate that an accelerator power supply with a SVPWM rectifier can solve the problems above well, and the output performance such as stability, tracking error and ripple current meet the requirements of the design. The achievement of prototype confirms that applying voltage-type SVPWM rectification technology in an accelerator power supply is feasible; and it provides a good reference for design and build of this new type of power supply. - Highlights: • Applying SVPWM rectification technology in an accelerator power supply improves its grid-side performance. • New Topology and its control strategies make an accelerator power supply have bidirectional power flow ability. • Hardware and software of controller provide a good reference for design of this new type of power supply.

  6. Harmonic Injection-Based Power Fluctuation Control of Three-Phase PV Systems under Unbalanced Grid Voltage Conditions

    Directory of Open Access Journals (Sweden)

    Nian-Cheng Zhou

    2015-02-01

    Full Text Available Unbalanced voltage will inevitably cause power and DC voltage fluctuations in a three-phase PV system. The deterioration of power quality will do great harm to the PV panels and the loads, so it is necessary to suppress the power fluctuations. This paper further explores the coefficients control strategy of PV converters under unbalanced voltage conditions, aiming to suppress power fluctuations by controlling the injection of some specific orders of current harmonics into the grid. In order to achieve this, the current reference of the PV inverter has been changed by bringing in two control coefficients, and the expression of each order of the current harmonics has been deduced. Based on the standards of PV systems, the regions from which the coefficients can be selected are determined. Then, by tuning these coefficients in the feasible regions, the output parameters (power fluctuation, current THD and odd harmonics can be controlled precisely. The model of this method is built and simulated in PSCAD/EMTDC, and as a result, it is shown that the power fluctuations can be restricted according to different power quality requirements.

  7. Monitoring the metering performance of an electronic voltage transformer on-line based on cyber-physics correlation analysis

    Science.gov (United States)

    Zhang, Zhu; Li, Hongbin; Tang, Dengping; Hu, Chen; Jiao, Yang

    2017-10-01

    Metering performance is the key parameter of an electronic voltage transformer (EVT), and it requires high accuracy. The conventional off-line calibration method using a standard voltage transformer is not suitable for the key equipment in a smart substation, which needs on-line monitoring. In this article, we propose a method for monitoring the metering performance of an EVT on-line based on cyber-physics correlation analysis. By the electrical and physical properties of a substation running in three-phase symmetry, the principal component analysis method is used to separate the metering deviation caused by the primary fluctuation and the EVT anomaly. The characteristic statistics of the measured data during operation are extracted, and the metering performance of the EVT is evaluated by analyzing the change in statistics. The experimental results show that the method successfully monitors the metering deviation of a Class 0.2 EVT accurately. The method demonstrates the accurate evaluation of on-line monitoring of the metering performance on an EVT without a standard voltage transformer.

  8. Containment-based Distributed Coordination Control to Achieve Both Bounded Voltage and Precise Current Sharing in Reverse-Droop-based DC Microgrid

    DEFF Research Database (Denmark)

    Han, Renke; Wang, Haojie; Jin, Zheming

    2017-01-01

    A highly flexible and reliable control strategy is proposed to achieve bounded voltage and precise current sharing, which is implemented in a reverse-droop-based dc Micro-Grid. To acquire the fast-dynamic response, the reverse droop control is used to replace the V-I droop control in the primary ...

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

    DEFF Research Database (Denmark)

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

    2017-01-01

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

  10. Evaluation of enhancements to Thevenin equivalent based methods for real-time voltage stability assessment

    DEFF Research Database (Denmark)

    Perez, Angel; Jóhannsson, Hjörtur; Østergaard, Jacob

    2014-01-01

    The possibilities offered by the use of Phasor Measurement Units (PMU) in real - time monitoring provide interesting ways to ensure secure operation of power systems. This paper studies the specific case of voltage stability and the possible improvements to the Thevenin equivalent methods, which...... is applied generally with local measurements. This paper uses the PMU measurements to calculate the grid transformation coefficients to obtain wide - area information. This is achieved by studying the generator's electromo tive force estimated using values in the coefficient transformation matrix...

  11. Dose estimate by personal music players based on weighted output voltage

    DEFF Research Database (Denmark)

    Hammershøi, Dorte; Ordoñez Pizarro, Rodrigo Eduardo; Christensen, Anders Tornvig

    2015-01-01

    not include the weighting principles necessary for sound sources close to the ears either, which constitutes an inverse head-related transfer function for the free- or diffuse field. The purpose of the present study is to assess the uncertainties in the dose estimate determined this way. Measurements for 20......The exposure by personal music players may in future be displayed to users, as described in the current draft of EN 50332-3. The suggested procedure includes a weighting of the electrical output voltages of the music player, and does not include the significance of the earphone sensitivity. It does...

  12. Voltage Feedback based Harmonic Compensation for an Offshore Wind Power Plant

    DEFF Research Database (Denmark)

    Chaudhary, Sanjay K.; Lascu, Cristian; Teodorescu, Remus

    2016-01-01

    the harmonic distortion at the point of common coupling within the planning level limits using harmonic compensation, which is usually done by passive filters. In this paper a novel active harmonic compensation technique using voltage feedback from a non-local bus has been proposed and analyzed. Its......When an offshore wind power plant is connected to the grid, there is a risk of amplification of certain harmonics and appearance resonances at the point of connection due to the interaction between the grid network and the wind power plant network. Hence, the plant developer is obliged to maintain...

  13. Community-Based Wetland Restoration Workshop in the Lower Ninth Ward, New Orleans

    Science.gov (United States)

    Wang, H. F.; Craig, L.; Ross, J. A.; Zepeda, L.; Carpenter, Q.

    2010-12-01

    Since 2007 a workshop class of University of Wisconsin-Madison students has participated in a community-based project in New Orleans to investigate the feasibility of restoring the Bayou Bienvenue Wetland Triangle (BBWT), which is adjacent to the Lower 9th Ward in New Orleans. This 440-acre region is currently open water but was a cypress forest until the 1970s. Restoration would provide protection from storm surges, restored ecological services, and recreational use. The workshop introduced students to the multidisciplinary skills needed to work effectively with the complex and interconnected issues within a project involving many stakeholders. The stakeholders included the Center for Sustainable Engagement and Development (CSED), Lower 9th Ward residents, non-profits (e.g., Sierra Club, Environmental Defense, Lake Pontchartrain Basin Foundation, National Wildlife Federation), government agencies (e.g., New Orleans Sewerage and Water Board, Army Corps of Engineers), neighborhood groups (e.g., Holy Cross Neighborhood Association, The Village), and universities (Tulane, U. of New Orleans, LSU, U. Colorado-Denver, Southeastern Louisiana). The course ran initially as a Water Resources Management practicum in the first two summers and then as a broader multidisciplinary project with student expertise in hydrology, social science, law, planning, policy analysis, community development, GIS, public health, environmental education and ecological restoration. The project divided into three main components: wetland science, social science, and land tenure and planning. Principal activities in wetland science were to monitor water levels and water quality, inventory flora and fauna, and plant grasses on small “floating islands.” The principal social science activity was to conduct a neighborhood survey about knowledge of the wetland and interest in its restoration. The land tenure and planning activity was to investigate ownership and transfer of property within the

  14. Bio-Root and Implant-Based Restoration as a Tooth Replacement Alternative.

    Science.gov (United States)

    Gao, Z H; Hu, L; Liu, G L; Wei, F L; Liu, Y; Liu, Z H; Fan, Z P; Zhang, C M; Wang, J S; Wang, S L

    2016-06-01

    We previously reported that dental stem cell-mediated bioengineered tooth root (bio-root) regeneration could restore tooth loss in a miniature pig model. As a potential new method for tooth restoration, it is essential to compare this method with the widely used commercial dental implant-based method of tooth restoration. Tooth loss models were created by extracting mandibular incisors from miniature pigs. Allogeneic periodontal ligament stem cells (PDLSCs) and dental pulp stem cells (DPSCs) were isolated and cultured. A PDLSC sheet was prepared by adding 20.0 µg/mL vitamin C to the culture medium; in addition, a hydroxyapatite tricalcium phosphate (HA/TCP)/DPSC graft was fabricated and cultured in a 3-dimensional culture system. A total of 46 bio-root implantations and 9 dental implants were inserted, and crown restorations were performed 6 mo after implantation. Histological, radiological, biomechanical, and elemental analyses were used to evaluate and compare tissue-engineered bio-roots and dental implants to the natural tooth roots. After 6 mo, both computed tomography scans and histological examinations showed that root-like structures and dentin-like tissues had formed. Three months after crown restoration, clinical assessments revealed that tooth function was equivalent in the regenerated bio-root and the dental implant. Biomechanical testing showed that the bio-roots were similar to natural tooth roots in compressive strength, modulus of elasticity, and torsional force; however, these properties were significantly higher in the dental implants. Elemental analysis revealed a higher similarity in elemental composition between bio-roots and natural tooth roots than between bio-roots and dental implants. However, the dental implant success rate was 100% (9 of 9) and the bio-root success rate was only 22% (10 of 46). Taken together, we showed that an allogeneic HA/TCP/DPSC/PDLSC sheet could successfully build a bio-root with structure and function similar to

  15. Voltage-induced switching dynamics based on an AZO/VO2/AZO sandwiched structure

    Science.gov (United States)

    Xiao, Han; Li, Yi; Fang, Baoying; Wang, Xiaohua; Liu, Zhimin; Zhang, Jiao; Li, Zhengpeng; Huang, Yaqin; Pei, Jiangheng

    2017-11-01

    A vanadium dioxide (VO2) thin film was prepared on an Al-doped ZnO (AZO) conductive glass substrate by DC magnetron sputtering and a post-annealing process. The AZO/VO2/AZO sandwiched structure was fabricated on the VO2/AZO composite film using photolithography and a chemical etching process. The composition, microstructure and optical properties of the VO2/AZO composite film were tested. The results showed that the VO2/AZO composite film was poly-crystalline and the AZO layer did not change the preferred growth orientation of VO2. When the voltage was applied on both of the transparent conductive layers of the AZO/VO2/AZO sandwiched structure, an abrupt change in the current was observed at different temperatures. The temperature dependence of I-V characteristic curves for the AZO/VO2/AZO sandwiched structure was analyzed. The phase transition voltage value is 7.5 V at 20 °C and decreases with increasing temperature.

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

    OpenAIRE

    Okuma, Takanori; Yasuura, Hiroto

    2001-01-01

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

  17. Light-curing Time and Aging Effects on the Nanomechanical Properties of Methacrylate- and Silorane-based Restorations

    OpenAIRE

    Catelan, A.; Pollard, T; Bedran-Russo, A.K.; Santos, Paulo Henrique dos [UNESP; AMBROSANO G.M.B.; Aguiar, F. H. B.

    2014-01-01

    The aim of this study was to assess the influence of light-curing time on the nanohardness (H) and reduced elastic modulus (E-r) of components (underlying dentin, hybrid layer, adhesive, and composite) of methacrylate- and silorane-based restorations after 24 hours and six months of storage. Class II slot preparations were carried out in human molars (n=3) and restored with methacrylate (Clearfil SE Bond [Kuraray] + Filtek Z250 [3M ESPE]) or silorane (LS restorative system [3M ESPE]) restorat...

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

    Directory of Open Access Journals (Sweden)

    Vukić Vladimir Đ.

    2012-01-01

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

  19. A 24-month Evaluation of Amalgam and Resin-Based Composite Restorations: Findings from The National Dental Practice-Based Research Network

    Science.gov (United States)

    McCracken, Michael S.; Gordan, Valeria V.; Litaker, Mark S.; Funkhouser, Ellen; Fellows, Jeffrey L.; Shamp, Douglass G.; Qvist, Vibeke; Meral, Jeffrey S.; Gilbert, Gregg H.

    2013-01-01

    Background Knowing which factors influence restoration longevity can help clinicians make sound treatment decisions. The authors analyzed data from the National Dental Practice-Based Research Network to identify predictors of early failures of amalgam and resin-based composite (RBC) restorations. Methods This prospective cohort study gathered information from clinicians and offices participating in the network. Clinicians completed a baseline data collection form at the time of restoration placement, and annually thereafter. Data collected included patient factors, practice factors, and dentist factors, and were analyzed using mixed-model logistic regression. Results A total of 226 practitioners followed 6,218 direct restorations in 3,855 patients; 386 restorations failed (6.6 percent) during the mean follow-up period of 23.7 (SD 8.8) months. The number of tooth surfaces restored at baseline predicted subsequent restoration failure; large restorations were over 4 times more likely to fail. Material was not significantly associated with longevity; neither was tooth type. Patient age was highly associated with failure (p<0.0001). The failure rate for children was 5 percent, compared to 12 percent in persons 65 years old or older. Dentist gender and practice workload were significantly associated with restoration longevity. Conclusions In this prospective cohort study, these factors significantly predicted an increased failure rate for amalgam and RBC restorations: older patient age and a higher number of surfaces restored at baseline, with other key baseline variables taken into account. Material choice was not significantly predictive in these early results. Clinical Implications Understanding risk factors for early restoration failure may lead to more-effective patient care. PMID:23729455

  20. Marginal integrity of restorations produced with a model composite based on polyhedral oligomeric silsesquioxane (POSS

    Directory of Open Access Journals (Sweden)

    Luciano Ribeiro CORREA NETTO

    2015-10-01

    Full Text Available Marginal integrity is one of the most crucial aspects involved in the clinical longevity of resin composite restorations.Objective To analyze the marginal integrity of restorations produced with a model composite based on polyhedral oligomeric silsesquioxane (POSS.Material and Methods A base composite (B was produced with an organic matrix with UDMA/TEGDMA and 70 wt.% of barium borosilicate glass particles. To produce the model composite, 25 wt.% of UDMA were replaced by POSS (P25. The composites P90 and TPH3 (TP3 were used as positive and negative controls, respectively. Marginal integrity (%MI was analyzed in bonded class I cavities. The volumetric polymerization shrinkage (%VS and the polymerization shrinkage stress (Pss - MPa were also evaluated.Results The values for %MI were as follows: P90 (100% = TP3 (98.3% = B (96.9% > P25 (93.2%, (p<0.05. The %VS ranged from 1.4% (P90 to 4.9% (P25, while Pss ranged from 2.3 MPa (P90 to 3.9 MPa (B. For both properties, the composite P25 presented the worst results (4.9% and 3.6 MPa. Linear regression analysis showed a strong positive correlation between %VS and Pss (r=0.97, whereas the correlation between Pss and %MI was found to be moderate (r=0.76.Conclusions The addition of 25 wt.% of POSS in methacrylate organic matrix did not improve the marginal integrity of class I restorations. Filtek P90 showed lower polymerization shrinkage and shrinkage stress when compared to the experimental and commercial methacrylate composite.

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

    Directory of Open Access Journals (Sweden)

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

    2010-01-01

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

  2. New layer-based imaging and rapid prototyping techniques for computer-aided design and manufacture of custom dental restoration.

    Science.gov (United States)

    Lee, M-Y; Chang, C-C; Ku, Y C

    2008-01-01

    Fixed dental restoration by conventional methods greatly relies on the skill and experience of the dental technician. The quality and accuracy of the final product depends mostly on the technician's subjective judgment. In addition, the traditional manual operation involves many complex procedures, and is a time-consuming and labour-intensive job. Most importantly, no quantitative design and manufacturing information is preserved for future retrieval. In this paper, a new device for scanning the dental profile and reconstructing 3D digital information of a dental model based on a layer-based imaging technique, called abrasive computer tomography (ACT) was designed in-house and proposed for the design of custom dental restoration. The fixed partial dental restoration was then produced by rapid prototyping (RP) and computer numerical control (CNC) machining methods based on the ACT scanned digital information. A force feedback sculptor (FreeForm system, Sensible Technologies, Inc., Cambridge MA, USA), which comprises 3D Touch technology, was applied to modify the morphology and design of the fixed dental restoration. In addition, a comparison of conventional manual operation and digital manufacture using both RP and CNC machining technologies for fixed dental restoration production is presented. Finally, a digital custom fixed restoration manufacturing protocol integrating proposed layer-based dental profile scanning, computer-aided design, 3D force feedback feature modification and advanced fixed restoration manufacturing techniques is illustrated. The proposed method provides solid evidence that computer-aided design and manufacturing technologies may become a new avenue for custom-made fixed restoration design, analysis, and production in the 21st century.

  3. A Complex Permittivity Based Sensor for the Electrical Characterization of High-Voltage Transformer Oils

    Directory of Open Access Journals (Sweden)

    Panayota Vassiliou

    2005-05-01

    Full Text Available This work investigates the use of a specially designed cylindrical metal cell, inorder to obtain complex permittivity and tanδ data of highly insulating High Voltage (HVtransformer oil samples. The data are obtained at a wide range of frequencies and operationtemperatures to demonstrate the polarization phenomena and the thermally stimulatedeffects. Such complex permittivity measurements may be utilized as a criterion for theservice life prediction of oil field electrical equipment (OFEE. Therefore, by one set ofmeasurements on a small oil volume, data may be provided on the impending termination,or continuation of the transformer oil service life. The oil incorporating cell, attached to theappropriate measuring units, could be described as a complex permittivity sensor. In thiswork, the acquired dielectric data from a great number of operating distribution networkpower transformers were correlated to corresponding physicochemical ones to demonstratethe future potential employment of the proposed measuring technique.

  4. A Complex Permittivity Based Sensor for the Electrical Characterization of High-Voltage Transformer Oils

    Science.gov (United States)

    Dervos, Constantine T.; Paraskevas, Christos D.; Skafidas, Panayotis D.; Vassiliou, Panayota

    2005-01-01

    This work investigates the use of a specially designed cylindrical metal cell, in order to obtain complex permittivity and tanδ data of highly insulating High Voltage (HV) transformer oil samples. The data are obtained at a wide range of frequencies and operation temperatures to demonstrate the polarization phenomena and the thermally stimulated effects. Such complex permittivity measurements may be utilized as a criterion for the service life prediction of oil field electrical equipment (OFEE). Therefore, by one set of measurements on a small oil volume, data may be provided on the impending termination, or continuation of the transformer oil service life. The oil incorporating cell, attached to the appropriate measuring units, could be described as a complex permittivity sensor. In this work, the acquired dielectric data from a great number of operating distribution network power transformers were correlated to corresponding physicochemical ones to demonstrate the future potential employment of the proposed measuring technique.

  5. Matlab/Simulink Based Analysis of Voltage Source Inverter With Space Vector Modulation

    Directory of Open Access Journals (Sweden)

    Auzani Jidin

    2009-04-01

    Full Text Available Space vector modulation (SVM is the best modulation technique to drive 3-phase load such as 3-phase induction motor. In this paper, the pulse width modulation strategy with SVM is analyzed in detail. The modulation strategy uses switching time calculator to calculate the timing of voltage vector applied to the three-phase balanced-load. The principle of the space vector modulation strategy is performed using Matlab/Simulink. The simulation result indicates that this algorithm is flexible and suitable to use for advance vector control. The strategy of the switching minimizes the distortion of load current as well as loss due to minimize number of commutations in the inverter.

  6. FPGA-based voltage and current dual drive system for high frame rate electrical impedance tomography.

    Science.gov (United States)

    Khan, Shadab; Manwaring, Preston; Borsic, Andrea; Halter, Ryan

    2015-04-01

    Electrical impedance tomography (EIT) is used to image the electrical property distribution of a tissue under test. An EIT system comprises complex hardware and software modules, which are typically designed for a specific application. Upgrading these modules is a time-consuming process, and requires rigorous testing to ensure proper functioning of new modules with the existing ones. To this end, we developed a modular and reconfigurable data acquisition (DAQ) system using National Instruments' (NI) hardware and software modules, which offer inherent compatibility over generations of hardware and software revisions. The system can be configured to use up to 32-channels. This EIT system can be used to interchangeably apply current or voltage signal, and measure the tissue response in a semi-parallel fashion. A novel signal averaging algorithm, and 512-point fast Fourier transform (FFT) computation block was implemented on the FPGA. FFT output bins were classified as signal or noise. Signal bins constitute a tissue's response to a pure or mixed tone signal. Signal bins' data can be used for traditional applications, as well as synchronous frequency-difference imaging. Noise bins were used to compute noise power on the FPGA. Noise power represents a metric of signal quality, and can be used to ensure proper tissue-electrode contact. Allocation of these computationally expensive tasks to the FPGA reduced the required bandwidth between PC, and the FPGA for high frame rate EIT. In 16-channel configuration, with a signal-averaging factor of 8, the DAQ frame rate at 100 kHz exceeded 110 frames s (-1), and signal-to-noise ratio exceeded 90 dB across the spectrum. Reciprocity error was found to be for frequencies up to 1 MHz. Static imaging experiments were performed on a high-conductivity inclusion placed in a saline filled tank; the inclusion was clearly localized in the reconstructions obtained for both absolute current and voltage mode data.

  7. Photoelastic analysis of stress generated by a silorane-based restoration system

    Directory of Open Access Journals (Sweden)

    Murilo Baena Lopes

    2011-08-01

    Full Text Available Silorane-based composite, an epoxy material, was marketed as promising less polymerization contraction than conventional restorative materials. The aim of this study was to evaluate, by means of photoelasticity, the polymerization stress generated by a silorane-based composite. Thirty photoelastic rings with orifices measuring 5 mm (d × 3 mm (h were prepared and divided into 6 groups (n = 5 according to the material tested. The inside walls of the rings were sandblasted with aluminum oxide, after which the restorative materials were inserted into the orifices and photoactivated according to the manufacturer's instructions. The specimens were analyzed and the visual representation of the stress was measured considering the isochromatic ring of first order. The data were converted to MPa and subjected to ANOVA and Tukey's test (α= 0.05. The adhesive Filtek P-90 (G5 showed high contraction stress (p 0.05. The composite Filtek P-90 showed similar contraction stress compared to the conventional composite and, additionally, its adhesive showed higher stress than did the etch-and-rinse 2-step adhesive.

  8. Advancing stream restoration design: a science-based approach using data and methodologies from the agencies

    Science.gov (United States)

    Jessica Palazzolo; Joshua Robinson; Phillip Ellis

    2016-01-01

    Ecosystem restoration design is a relatively new field of work that requires multi-disciplinary expertise in the natural sciences. Although the field is new, federal agencies and public institutions have spent several decades and millions of dollars researching the sciences and methods that underly restoration activities. However, many restoration practitioners are...

  9. DC-Link Capacitor Voltage Regulation for Three-Phase Three-Level Inverter-Based Shunt Active Power Filter with Inverted Error Deviation Control

    Directory of Open Access Journals (Sweden)

    Yap Hoon

    2016-07-01

    Full Text Available A new control technique known as inverted error deviation (IED control is incorporated into the main DC-link capacitor voltage regulation algorithm of a three-level neutral-point diode clamped (NPC inverter-based shunt active power filter (SAPF to enhance its performance in overall DC-link voltage regulation so as to improve its harmonics mitigation performances. In the SAPF controller, DC-link capacitor voltage regulation algorithms with either the proportional-integral (PI or fuzzy logic control (FLC technique have played a significant role in maintaining a constant DC-link voltage across the DC-link capacitors. However, both techniques are mostly operated based on a direct voltage error manipulation approach which is insufficient to address the severe DC-link voltage deviation that occurs during dynamic-state conditions. As a result, the conventional algorithms perform poorly with large overshoot, undershoot, and slow response time. Therefore, the IED control technique is proposed to precisely address the DC-link voltage deviation. To validate effectiveness and feasibility of the proposed algorithm, simulation work in MATLAB-Simulink and experimental implementation utilizing a TMS320F28335 Digital Signal Processor (DSP are performed. Moreover, conventional algorithms with PI and FLC techniques are tested too for comparison purposes. Both simulation and experimental results are presented, confirming the improvement achieved by the proposed algorithm in terms of accuracy and dynamic response in comparison to the conventional algorithms.

  10. Benchmarking of Voltage Sag Generators

    DEFF Research Database (Denmark)

    Yang, Yongheng; Blaabjerg, Frede; Zou, Zhixiang

    2012-01-01

    to guide these grid-connected distributed power generation systems. In order to verify the response of such systems for voltage disturbance, mainly for evaluation of voltage sags/dips, a Voltage Sag Generator (VSG) is needed. This paper evaluates such sag test devices according to IEC 61000 in order...... to provide cheaper solutions to test against voltage sags. Simulation and experimental results demonstrate that the shunt impedance based VSG solution is the easiest and cheapest one for laboratory test applications. The back-to-back fully controlled converter based VSG is the most flexible solution......The increased penetration of renewable energy systems, like photovoltaic and wind power systems, rises the concern about the power quality and stability of the utility grid. Some regulations for Low Voltage Ride-Through (LVRT) for medium voltage or high voltage applications, are coming into force...

  11. The effect of a nanofilled resin-based coating on water absorption by teeth restored with glass ionomer.

    Science.gov (United States)

    Hankins, Amanda D; Hatch, Robert H; Benson, Jarred H; Blen, Bernard J; Tantbirojn, Daranee; Versluis, Antheunis

    2014-04-01

    A nanofilled, resin-based light-cured coating (G-Coat Plus, GC America, Alsip, Ill.) may reduce water absorption by glass ionomers. The authors investigated this possibility by measuring cuspal flexure caused by swelling of glass ionomer-restored teeth. The authors cut large mesio-occlusodistal slots (4-millimeter wide, 4-mm deep) in 12 extracted premolars and restored them with a glass ionomer cement (Fuji IX GP Extra, GC America). Six teeth were coated, and the other six were uncoated controls. The authors digitized the teeth in three dimensions by using an optical scanner after preparation and restoration and during an eight-week storage in water. They calculated cuspal flexure and analyzed the results by using an analysis of variance and Student-Newman-Keuls post hoc tests (significance level .05). They used dye penetration along the interface to verify bonding. Inward cuspal flexure indicated restoration shrinkage. Coated restorations had significantly higher flexure (mean [standard deviation], -11.9 [3.5] micrometers) than did restorations without coating (-7.3 [1.5] μm). Flexure in both groups decreased significantly (P water storage and, after eight weeks, it changed to expansion for uncoated control restorations. Dye penetration along the interfaces was not significant, which ruled out debonding as the cause of cuspal relaxation. Teeth restored with glass ionomer cement exhibited shrinkage, as seen by inward cuspal flexure. The effect of the protective coating on water absorption was evident in the slower shrinkage compensation. The study results show that teeth restored with glass ionomers exhibited setting shrinkage that deformed tooth cusps. Water absorption compensated for the shrinkage. Although the coating may be beneficial for reducing water absorption, it also slows the shrinkage compensation rate (that is, the rate that hygroscopic expansion compensates for cuspal flexure from shrinkage).

  12. Voltage regulation of the Y-source boost DC-DC converter considering effects of leakage inductances based on cascaded sliding-mode control

    DEFF Research Database (Denmark)

    Ahmadzadeh, Soheil; Markadeh, Gholamreza Arab; Blaabjerg, Frede

    2017-01-01

    have been considered. Also, an exposition of a variable structure control approach is mentioned. The method employs cascaded slidingmode control (CSMC) to output voltage regulation of the converter. The stability and robustness of the CSMC against the variation of reference voltages......In this study, a sliding mode-based controller is designed for regulating the output voltage of a high step-up DC-DC converter with three coupled inductors called Y-source impedance network. As Y-source converter can provide a very high boost at a lower shoot-through duty cycle of the switch...

  13. Low-voltage organic electronics based on a gate-tunable injection barrier in vertical graphene-organic semiconductor heterostructures.

    Science.gov (United States)

    Hlaing, Htay; Kim, Chang-Hyun; Carta, Fabio; Nam, Chang-Yong; Barton, Rob A; Petrone, Nicholas; Hone, James; Kymissis, Ioannis

    2015-01-14

    The vertical integration of graphene with inorganic semiconductors, oxide semiconductors, and newly emerging layered materials has recently been demonstrated as a promising route toward novel electronic and optoelectronic devices. Here, we report organic thin film transistors based on vertical heterojunctions of graphene and organic semiconductors. In these thin heterostructure devices, current modulation is accomplished by tuning of the injection barriers at the semiconductor/graphene interface with the application of a gate voltage. N-channel devices fabricated with a thin layer of C60 show a room temperature on/off ratio >10(4) and current density of up to 44 mAcm(-2). Because of the ultrashort channel intrinsic to the vertical structure, the device is fully operational at a driving voltage of 200 mV. A complementary p-channel device is also investigated, and a logic inverter based on two complementary transistors is demonstrated. The vertical integration of graphene with organic semiconductors via simple, scalable, and low-temperature fabrication processes opens up new opportunities to realize flexible, transparent organic electronic, and optoelectronic devices.

  14. UAV remote sensing atmospheric degradation image restoration based on multiple scattering APSF estimation

    Science.gov (United States)

    Qiu, Xiang; Dai, Ming; Yin, Chuan-li

    2017-09-01

    Unmanned aerial vehicle (UAV) remote imaging is affected by the bad weather, and the obtained images have the disadvantages of low contrast, complex texture and blurring. In this paper, we propose a blind deconvolution model based on multiple scattering atmosphere point spread function (APSF) estimation to recovery the remote sensing image. According to Narasimhan analytical theory, a new multiple scattering restoration model is established based on the improved dichromatic model. Then using the L0 norm sparse priors of gradient and dark channel to estimate APSF blur kernel, the fast Fourier transform is used to recover the original clear image by Wiener filtering. By comparing with other state-of-the-art methods, the proposed method can correctly estimate blur kernel, effectively remove the atmospheric degradation phenomena, preserve image detail information and increase the quality evaluation indexes.

  15. Effect of Zirconia Thickness on the Tensile Stress of Zirconia Based All-Ceramic Restorations

    Directory of Open Access Journals (Sweden)

    Masood Shiezadeh

    2015-09-01

    Full Text Available Introduction: The purpose of the presented study was to evaluate the effect of zirconia thickness on the tensile stress of zirconia based all-ceramic restorations. Methods: Twenty zirconia disks with 10mm diameter were prepared in two groups using CAD/CAM system. The thickness of zirconia was 0.5mm in first group and 0.3mm in second group. After sintering, 0.4mm glass ceramic porcelain was applied to each disk. Then, sintering and glazing of porcelain carried out. Instron testing machine with 1mm/min crosshead speed used to evaluate the failure load of the samples. Biaxial Flexural strength standard formula employed to calculate tensile stress of specimens. Statistical analysis performed using SPSS software. Results: Although data analysis showed more maximum tensile stress in 1st group, no significant differences were found between two groups. Conclusion: Zirconia with 0.5mm and 0.3mm thicknesses cause similar tensile stress in all-ceramic restorations and thickness of these laminates could be reduced to 0.7mm.

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

    DEFF Research Database (Denmark)

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

    2017-01-01

    This paper reviews and analyzes the existing voltage control methods of distributed solar PV inverters to improve the voltage regulation and thereby the hosting capacity of a low-voltage distribution network. A novel coordinated voltage control method is proposed based on voltage sensitivity...... analysis, which is simple for computation and requires moderate automation and communication infrastructure. The proposed method is suitable for a hierarchical control structure where a supervisory controller has the provision to adapt the settings of local PV inverter controllers for overall system...

  17. Transformer-based asymmetrical embedded Z-source neutral point clamped inverters with continuous input current and enhanced voltage boost capability

    DEFF Research Database (Denmark)

    Mo, W.; Loh, Poh Chiang; Blaabjerg, Frede

    2013-01-01

    Z-source Neutral Point Clamped (NPC) inverters were introduced to integrate both the advantages of Z-source inverters and NPC inverters. However, traditional Z-source inverters suffer from high voltage stress and chopping input current. This paper proposes six types transformer-based impedance......-source NPC inverters which have enhanced voltage boost capability and continuous input current by utilizing of transformer and embedded dc source configuration. Experimental results are presented to verify the theory validation....

  18. Simulation Analysis for Opening Performance of Medium Voltage Vacuum Circuit Breaker Based on ADAMS and Maxwell

    Directory of Open Access Journals (Sweden)

    Ding Xianliang

    2017-01-01

    Full Text Available The circuit breakers play a important role in control and protect the power systemand the vacuum circuit breaker has beenwidely used in the field of medium voltage with its excellent opening performance.Virtual prototyping technology is alsobecamemore and more popularin design and optimization of the vacuum circuit breaker. In this paper, the electromagnetic simulation software Ansoft Maxwell is used to analyze the electric repulsion of the circuit breaker in the case of open the rated short circuit breaking current. The 3D model that wasbuilt by CREOis imported into ADAMS. Thenconstraints, contact force, and the electric repulsion forcethat was analysezed in Ansoft Maxwell is added into the 3D model.Therefore, we can carry on the multi-body dynamics simulation to the 3D model. Then We can get the openingperformance of the vacuum circuit breakerin the condition of open circuit rated short circuit breaking current. The simulation results show that the circuit breaker can still meet the performance requirements in the condition of open circuit rated short circuit breaking current.

  19. Comparative evaluation of shear bond strength and microleakage of tricalcium silicate-based restorative material and radioopaque posterior glass ionomer restorative cement in primary and permanent teeth: An in vitro study

    Directory of Open Access Journals (Sweden)

    Vignesh Guptha Raju

    2014-01-01

    Full Text Available Background: Restoration of carious primary molars is still a major concern while treating the young children that too in deep carious lesion which extends below the cemento-enamel junction (CEJ where pulp protection and achieving adequate marginal seal are very important to prevent secondary caries. The needs were met with the development of new materials. One such of new bioactive material is tricalcium silicate-based restorative material (Biodentine, recommended for restoring deep lesions. Aim: To evaluate and compare shear bond strength and microleakage of tricalcium silicate-based restorative material (Biodentine and glass ionomer cement (Fuji IX GP in primary and permanent teeth. Materials and Methods: Occlusal surface of crowns were ground flat. PVC molds were stabilized over flat dentin surface and filled with tricalcium silicate-based restorative material (Biodentine/glass ionomer cement (Fuji IX GP according to group ascertained. Shear bond strength was evaluated using universal testing machine (INSTRON. Standardized Class II cavities were prepared on both primary and permanent teeth, and then restored with tricalcium silicate-based restorative material (Biodentine/glass ionomer cement (Fuji IX GP according to group ascertained, over which composite resin material was restored using an open sandwich technique. Microleakage was assessed using dye penetration. Microleakage was examined using a stereomicroscope. Results: Results showed that glass ionomer cement (Fuji IX GP exhibited better shear bond strength than tricalcium silicate-based restorative material (Biodentine. Mean microleakage score for glass ionomer cement (Fuji IX GP in permanent teeth was 1.52 and for primary teeth was 1.56. The mean microleakage for tricalcium silicate-based restorative material (Biodentine in permanent teeth was 0.76 and for primary teeth was 0.60. Glass ionomer cement (Fuji IX GP exhibited more microleakage than tricalcium silicate-based restorative

  20. Comparative evaluation of shear bond strength and microleakage of tricalcium silicate-based restorative material and radioopaque posterior glass ionomer restorative cement in primary and permanent teeth: an in vitro study.

    Science.gov (United States)

    Raju, Vignesh Guptha; Venumbaka, Nilaya Reddy; Mungara, Jayanthi; Vijayakumar, Poornima; Rajendran, Sakthivel; Elangovan, Arun

    2014-01-01

    Restoration of carious primary molars is still a major concern while treating the young children that too in deep carious lesion which extends below the cemento-enamel junction (CEJ) where pulp protection and achieving adequate marginal seal are very important to prevent secondary caries. The needs were met with the development of new materials. One such of new bioactive material is tricalcium silicate-based restorative material (Biodentine), recommended for restoring deep lesions. To evaluate and compare shear bond strength and microleakage of tricalcium silicate-based restorative material (Biodentine) and glass ionomer cement (Fuji IX GP) in primary and permanent teeth. Occlusal surface of crowns were ground flat. PVC molds were stabilized over flat dentin surface and filled with tricalcium silicate-based restorative material (Biodentine)/glass ionomer cement (Fuji IX GP) according to group ascertained. Shear bond strength was evaluated using universal testing machine (INSTRON). Standardized Class II cavities were prepared on both primary and permanent teeth, and then restored with tricalcium silicate-based restorative material (Biodentine)/glass ionomer cement (Fuji IX GP) according to group ascertained, over which composite resin material was restored using an open sandwich technique. Microleakage was assessed using dye penetration. Microleakage was examined using a stereomicroscope. RESULTS showed that glass ionomer cement (Fuji IX GP) exhibited better shear bond strength than tricalcium silicate-based restorative material (Biodentine). Mean microleakage score for glass ionomer cement (Fuji IX GP) in permanent teeth was 1.52 and for primary teeth was 1.56. The mean microleakage for tricalcium silicate-based restorative material (Biodentine) in permanent teeth was 0.76 and for primary teeth was 0.60. Glass ionomer cement (Fuji IX GP) exhibited more microleakage than tricalcium silicate-based restorative material (Biodentine), which was statistically significant

  1. Study on high breakdown voltage GaN-based vertical field effect transistor with interfacial charge engineering for power applications

    Science.gov (United States)

    Du, Jiangfeng; Liu, Dong; Liu, Yong; Bai, Zhiyuan; Jiang, Zhiguang; Liu, Yang; Yu, Qi

    2017-11-01

    A high voltage GaN-based vertical field effect transistor with interfacial charge engineering (GaN ICE-VFET) is proposed and its breakdown mechanism is presented. This vertical FET features oxide trenches which show a fixed negative charge at the oxide/GaN interface. In the off-state, firstly, the trench oxide layer acts as a field plate; secondly, the n-GaN buffer layer is inverted along the oxide/GaN interface and thus a vertical hole layer is formed, which acts as a virtual p-pillar and laterally depletes the n-buffer pillar. Both of them modulate electric field distribution in the device and significantly increase the breakdown voltage (BV). Compared with a conventional GaN vertical FET, the BV of GaN ICE-VFET is increased from 1148 V to 4153 V with the same buffer thickness of 20 μm. Furthermore, the proposed device achieves a great improvement in the tradeoff between BV and on-resistance; and its figure of merit even exceeds the GaN one-dimensional limit.

  2. An accurate online calibration system based on combined clamp-shape coil for high voltage electronic current transformers.

    Science.gov (United States)

    Li, Zhen-hua; Li, Hong-bin; Zhang, Zhi

    2013-07-01

    Electronic transformers are widely used in power systems because of their wide bandwidth and good transient performance. However, as an emerging technology, the failure rate of electronic transformers is higher than that of traditional transformers. As a result, the calibration period needs to be shortened. Traditional calibration methods require the power of transmission line be cut off, which results in complicated operation and power off loss. This paper proposes an online calibration system which can calibrate electronic current transformers without power off. In this work, the high accuracy standard current transformer and online operation method are the key techniques. Based on the clamp-shape iron-core coil and clamp-shape air-core coil, a combined clamp-shape coil is designed as the standard current transformer. By analyzing the output characteristics of the two coils, the combined clamp-shape coil can achieve verification of the accuracy. So the accuracy of the online calibration system can be guaranteed. Moreover, by employing the earth potential working method and using two insulating rods to connect the combined clamp-shape coil to the high voltage bus, the operation becomes simple and safe. Tests in China National Center for High Voltage Measurement and field experiments show that the proposed system has a high accuracy of up to 0.05 class.

  3. Geometrical structure and interface dependence of bias stress induced threshold voltage shift in C60-based OFETs.

    Science.gov (United States)

    Ahmed, Rizwan; Kadashchuk, Andrey; Simbrunner, Clemens; Schwabegger, Günther; Baig, Muhammad Aslam; Sitter, Helmut

    2014-09-10

    The influence of the nature of interface between organic semiconductor and gate dielectric on bias stress electrical stability of n-type C60-based organic field effect transistors (OFETs) was studied. The bias stress induced threshold voltage (Vth) shift was found to depend critically on the OFET device structure: the direction of V(th) shift in top-gate OFETs was opposite to that in bottom-gate OFETs, while the use of the dual-gate OFET structure resulted in just very small variations in V(th). The opposite direction of Vth shift is attributed to the different nature of interfaces between C60 semiconductor and Parylene dielectric in these devices. The V(th) shift to more positive voltages upon bias stress in bottom-gate C60-OFET was similar to that observed for other n-type semiconductors and rationalized by electron trapping in the dielectric or at the gate dielectric/C60 interface. The opposite direction of Vth shift in top-gate C60-OFETs is attributed to free radical species created in the course of Parylene deposition on the surface of C60 during device fabrication, which produce plenty of hole traps. It was also realized that the dual-gate OFETs gives stable characteristics, which are immune to bias stress effects.

  4. Ultra-High Voltage DC Convertor Station Equipment Condition Data Access Technology Based on multi-Source Heterogeneous Fusion

    Science.gov (United States)

    Wang, Feng; Zhang, Bo-wen; Han, Shuai; Ren, Wei; Xu, Hai-jun; Fu, Long-ming

    2017-07-01

    With the large-scale construction of special high-voltage project, as well as power supply reliability, security, economic and other increasingly demanding, state monitoring equipment involved in more and more monitoring projects and more and more monitoring data, because these data exist in multiple isolated systems in the Ultra-High Voltage(UHV) AC-DC substation, there is no data sharing mechanism, so a holistic analysis, application and sharing approach for the data set will need a deep consideration. In this paper, the equipment condition monitoring system frame of the UHV converter station and the scheme of the equipment state data access of UHV converter station based on the multi-source and heterogeneous data fusion are presented. Then, data exchange technology of UHV equipment state early warning center was introduced, and a data access and conversion device in the Zhongzhou converter station was deployed to solve the timeliness and functionality difficult of the existing system to meet the requirements of UHV operation and maintenance support.

  5. Enabling steady graphite anode cycling with high voltage, additive-free, sulfolane-based electrolyte: Role of the binder

    Science.gov (United States)

    Zhang, Tong; de Meatza, Iratxe; Qi, Xin; Paillard, Elie

    2017-07-01

    We demonstrate here the possibility of operating both high voltage spinel and high mass loading graphite electrodes in a 1 M LiPF6 in SL/DMC (1/1, wt/wt) electrolyte without the use of additive. A crucial point for practical graphite electrode operation is the use of the cheaper and environmentally friendly carboxymethyl cellulose (CMC)/styrene-butadiene rubber (SBR) combination instead of the PVDF-based electrodes used in most laboratory studies. With this type of anode we also show the operation of a full Li-ion cell operating at 4.5 V without any additive and show that most of the Li+ transport limitation observed in half-cells are in fact due to the Li metal counter electrode. The anode binder influence is to be considered for the development of high voltage electrolytes lacking good intrinsic SEI building properties, as the anode binder does not affect cathode performance, contrary to most additives. It opens the route for further improvement by use of SEI forming additives (molecular and salts), keeping in mind the requirement for the cathode.

  6. Mitigation of voltage sag using DVR under feedback and ...

    African Journals Online (AJOL)

    Mitigation of voltage sag using DVR under feedback and feedforward control scheme. B Panda, S Behera. Abstract. The paper deals with Dynamic Voltage Restorer (DVR) that aims at the integration of series active filter with minimum VA handling. The DVR not only regulates the voltage at load end but also acts as series ...

  7. Multi-Objective Scheduling Optimization Based on a Modified Non-Dominated Sorting Genetic Algorithm-II in Voltage Source Converter−Multi-Terminal High Voltage DC Grid-Connected Offshore Wind Farms with Battery Energy Storage Systems

    Directory of Open Access Journals (Sweden)

    Ho-Young Kim

    2017-07-01

    Full Text Available Improving the performance of power systems has become a challenging task for system operators in an open access environment. This paper presents an optimization approach for solving the multi-objective scheduling problem using a modified non-dominated sorting genetic algorithm in a hybrid network of meshed alternating current (AC/wind farm grids. This approach considers voltage and power control modes based on multi-terminal voltage source converter high-voltage direct current (MTDC and battery energy storage systems (BESS. To enhance the hybrid network station performance, we implement an optimal process based on the battery energy storage system operational strategy for multi-objective scheduling over a 24 h demand profile. Furthermore, the proposed approach is formulated as a master problem and a set of sub-problems associated with the hybrid network station to improve the overall computational efficiency using Benders’ decomposition. Based on the results of the simulations conducted on modified institute of electrical and electronics engineers (IEEE-14 bus and IEEE-118 bus test systems, we demonstrate and confirm the applicability, effectiveness and validity of the proposed approach.

  8. Voltage Quality of Grid Connected Wind Turbines

    DEFF Research Database (Denmark)

    Chen, Zhe; Blaabjerg, Frede; Sun, Tao

    2004-01-01

    Grid connected wind turbines may cause quality problems, such as voltage variation and flicker. This paper discusses the voltage variation and flicker emission of grid connected wind turbines with doubly-fed induction generators. A method to compensate flicker by using a voltage source converter...... (VSC) based STATCOM is presented, which shows it is an efficient mean to improve voltage quality....

  9. RESTORING SAFETY: AN ATTACHMENT-BASED APPROACH TO CLINICAL WORK WITH A TRAUMATIZED TODDLER.

    Science.gov (United States)

    Ribaudo, Julie

    2016-01-01

    This clinical case study explores the integration of infancy research, brain development, attachment theory, and models of infant-parent/child-parent psychotherapy to address the needs of abused and neglected young children placed in foster or adoptive homes. Traumatized children employ defensive strategies to survive when there is no "good enough" caregiver (D.W. Winnicott, 1953, p. 94), and helping professionals can provide therapeutic experiences to develop or restore a child's sense of safety. With the case example of Anthony and his foster/adoptive parents, I illustrate how to manage and contain a traumatized child's terror, rage, and grief through therapeutic sessions with the parent and child together, and supportive parental guidance. I promote attention to the child's ability to self-integrate and to regulate his own affect, and encourages secure-base parental responses that facilitate a child's shift toward secure attachment behavior. © 2015 Michigan Association for Infant Mental Health.

  10. Enhanced Control of a DFIG-Based Wind-Power Generation System With Series Grid-Side Converter Under Unbalanced Grid Voltage Conditions

    DEFF Research Database (Denmark)

    Yao, Jun; Li, Hui; Chen, Zhe

    2013-01-01

    This paper presents an enhanced control method for a doubly fed induction generator (DFIG)-based wind-power generation system with series grid-side converter (SGSC) under unbalanced grid voltage conditions. The behaviors of the DFIG system with SGSC during network unbalance are described....... By injecting a series control voltage generated from the SGSC to balance the stator voltage, the adverse effects of voltage unbalance upon the DFIG, such as stator and rotor current unbalances, electromagnetic torque, and power pulsations, can be removed, and then the conventional vector control strategy...... for the rotor-side converter remains in full force under unbalanced conditions. Meanwhile, three control targets for the parallel grid-side converter (PGSC) are identified, including eliminating the oscillations in the total active power or reactive power, or eliminating negative-sequence current injected...

  11. Motion characteristics and output voltage analysis of micro-vibration energy harvester based on diamagnetic levitation

    Science.gov (United States)

    Ye, Zhitong; Duan, Zhiyong; Takahata, Kenichi; Su, Yufeng

    2015-01-01

    In this paper, the force analysis and output performance of the micro-vibration energy harvester are elaborated. The force of the floating magnet in the magnetic field of the lifting magnet is firstly analyzed. Using COMSOL™, the change of magnetic force exerted on the floating magnet versus the vertical distance and the horizontal eccentric distance is obtained for different lifting magnets of a cylinder, a ring and an inner cylinder plus an outer ring, respectively. When the distance between the lifting and floating magnets ranges from 7.3 to 8.1 mm, the change rate of the magnetic force versus the vertical distance for the inner cylinder plus outer ring structure is the smallest, whose value is 619 µN/mm. In other words, if the inner cylinder plus outer ring structure is used as the lifting magnet, the vibration space of the floating magnet is the largest, which is 8 and 7.6 % larger than the cylinder and ring lifting magnets, respectively. The horizontal restoring forces of the three structures are substantially equal to each other at the horizontal eccentric distance of 4 mm, which is around 860 µN. Then the equilibrium position change of the floating magnet is discussed when the energy harvester is in an inclined position. Finally, by the analysis of the vibration model, the output performances of the energy harvester are comparatively calculated under the vertical and inclined positions. At the natural frequency of 6.93 Hz, the maximum power of 66.7 µW is generated.

  12. Schottky bipolar I-MOS: An I-MOS with Schottky electrodes and an open-base BJT configuration for reduced operating voltage

    Science.gov (United States)

    Kannan, N.; Kumar, M. Jagadesh

    2017-04-01

    In this paper, we have proposed a novel impact ionization MOS (I-MOS) structure, called the Schottky bipolar I-MOS, with Schottky source and drain electrodes and utilizing the open-base bipolar junction transistor (BJT) configuration for achieving reduction in the operating voltage of the I-MOS transistor. We report, using 2-D simulations, a low operating voltage (∼1.1 V) and a low subthreshold swing (∼3.6 mV/Decade). For the corresponding p-i-n I-MOS, the operating voltage is ∼5.5 V. The operating voltage of the Schottky bipolar I-MOS is the lowest reported operating voltage for silicon based I-MOS transistors. The nearly 80% reduction in the operating voltage of the Schottky bipolar I-MOS makes it suitable for applications requiring low operating voltages. The Schottky bipolar I-MOS is also expected to have an improved reliability over the p-i-n I-MOS since high energy carriers, induced by impact ionization near the drain, do not have to pass under the gate region in the channel. The use of Schottky contacts instead of heavily doped source and drain regions and the low channel doping level reduces the required thermal budget for device fabrication. The low operating voltage, low subthreshold swing and possibly improved reliability of the Schottky bipolar I-MOS, makes it a potential solution for applications where steep subthreshold slope transistors are being explored as alternative to the conventional MOS transistor.

  13. Developing New Coastal Forest Restoration Products Based on Landsat, ASTER, and MODIS Data

    Science.gov (United States)

    Spruce, Joseph P.; Graham, William; Smoot, James

    2009-01-01

    This paper discusses an ongoing effort to develop new geospatial information products for aiding coastal forest restoration and conservation efforts in coastal Louisiana and Mississippi. This project employs Landsat, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data in conjunction with airborne elevation data to compute coastal forest cover type maps and change detection products. Improved forest mapping products are needed to aid coastal forest restoration and management efforts of State and Federal agencies in the Northern Gulf of Mexico (NGOM) region. In particular, such products may aid coastal forest land acquisition and conservation easement procurements. This region's forests are often disturbed and subjected to multiple biotic and abiotic threats, including subsidence, salt water intrusion, hurricanes, sea-level rise, insect-induced defoliation and mortality, altered hydrology, wildfire, and conversion to non-forest land use. In some cases, such forest disturbance has led to forest loss or loss of regeneration capacity. In response, a case study was conducted to assess and demonstrate the potential of satellite remote sensing products for improving forest type maps and for assessing forest change over the last 25 years. Change detection products are needed for assessing risks for specific priority coastal forest types, such as live oak and baldcypress-dominated forest. Preliminary results indicate Landsat time series data are capable of generating the needed forest type and change detection products. Useful classifications were obtained using 2 strategies: 1) general forest classification based on use of 3 seasons of Landsat data from the same year; and 2) classification of specific forest types of concern using a single date of Landsat data in which a given targeted type is spectrally distinct compared to adjacent forested cover. When available, ASTER data was

  14. A model-based radiography restoration method based on simple scatter-degradation scheme for improving image visibility

    Science.gov (United States)

    Kim, K.; Kang, S.; Cho, H.; Kang, W.; Seo, C.; Park, C.; Lee, D.; Lim, H.; Lee, H.; Kim, G.; Park, S.; Park, J.; Kim, W.; Jeon, D.; Woo, T.; Oh, J.

    2018-02-01

    In conventional planar radiography, image visibility is often limited mainly due to the superimposition of the object structure under investigation and the artifacts caused by scattered x-rays and noise. Several methods, including computed tomography (CT) as a multiplanar imaging modality, air-gap and grid techniques for the reduction of scatters, phase-contrast imaging as another image-contrast modality, etc., have extensively been investigated in attempt to overcome these difficulties. However, those methods typically require higher x-ray doses or special equipment. In this work, as another approach, we propose a new model-based radiography restoration method based on simple scatter-degradation scheme where the intensity of scattered x-rays and the transmission function of a given object are estimated from a single x-ray image to restore the original degraded image. We implemented the proposed algorithm and performed an experiment to demonstrate its viability. Our results indicate that the degradation of image characteristics by scattered x-rays and noise was effectively recovered by using the proposed method, which improves the image visibility in radiography considerably.

  15. Distributed Control of Inverter-Based Lossy Microgrids for Power Sharing and Frequency Regulation Under Voltage Constraints

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chin-Yao; Zhang, Wei

    2016-01-19

    This paper presents a new distributed control framework to coordinate inverter-interfaced distributed energy resources (DERs) in island microgrids. We show that under bounded load uncertainties, the proposed control method can steer the microgrid to a desired steady state with synchronized inverter frequency across the network and proportional sharing of both active and reactive powers among the inverters. We also show that such convergence can be achieved while respecting constraints on voltage magnitude and branch angle differences. The controller is robust under various contingency scenarios, including loss of communication links and failures of DERs. The proposed controller is applicable to lossy mesh microgrids with heterogeneous R/X distribution lines and reasonable parameter variations. Simulations based on various microgrid operation scenarios are also provided to show the effectiveness of the proposed control method.

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

    DEFF Research Database (Denmark)

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

    2015-01-01

    of the equivalent impedance with and without the delay effect of an LLCL-filter based grid-connected inverter. Their corresponding equivalent circuits for the purpose of resonance damping are given to identify whether the feedback coefficient should be negative or positive for the different state-feedback methods....... In this paper, different feedback coefficients like the proportional, derivative, integral, high pass and low pass feedback coefficients of the filter capacitor current and the LC-trap circuit voltage are investigated for damping the filter resonance. Active damping methods are analyzed by using the concept....... Then the stability of the different methods and the design of the feedback coefficient are analyzed and compared using root loci. Finally, experimental results are presented to validate the theoretical analysis....

  17. An evaluation of microleakage of various glass ionomer based restorative materials in deciduous and permanent teeth: An in vitro study

    Science.gov (United States)

    Singla, Teena; Pandit, I.K.; Srivastava, Nikhil; Gugnani, Neeraj; Gupta, Monika

    2011-01-01

    Aim To evaluate the microleakage of recently available glass ionomer based restorative materials (GC Fuji IX GP, GC Fuji VII, and Dyract) and compare their microleakage with the previously existing glass ionomer restorative materials (GC Fuji II LC) in primary and permanent teeth. Method One hundred and fifty (75 + 75) non-carious deciduous and permanent teeth were restored with glass ionomer based restorative materials after making class I cavities. Samples were subjected to thermocycling after storing in distilled water for 24 h. Two coats of nail polish were applied 1 mm short of restorative margins and samples sectioned buccolingually after storing in methylene blue dye for 24 h. Microleakage was assessed using stereomicroscope. Result Significant differences (P  0.05) were observed. It was found that there was no statistically significant difference when the means of microleakage of primary teeth were compared with those of permanent teeth. Conclusions GC Fuji IX GP showed maximum microleakage and GC Fuji VII showed least microleakage. PMID:23960526

  18. Structural and mechanical properties of a giomer-based bulk fill restorative in different curing conditions

    Directory of Open Access Journals (Sweden)

    Mustafa Sarp Kaya

    2018-01-01

    Full Text Available ABSTRACT Objective: The main goal of this study was to compare the polymerization degree of bulk-fill giomer resin cured with three different light-curing units (LCUs: a polywave third-generation (Valo; a monowave (DemiUltra: DU; and a second-generation LED (Optima 10: Opt LCUs by using structural and mechanical properties. Material and methods: Giomer samples of 2 and 4 mm cured with three LCUs were employed in vitro analysis. The degree of curing (DC% was determined with Fourier-Transform Infrared Spectroscopy (FTIR. Microstructural features were observed with scanning electron microscopy (SEM. Flexural strength (FS, compression strength (CS, elastic modulus and fracturing strain were determined for mechanical properties. Surface microhardness (SMH values were also measured. Oneway ANOVA, two-way analysis of variance and Tukey multiple comparison tests were used for statistically analyzing the FS and SMH. Results: DC% values were 58.2, 47.6, and 39.7 for the 2 mm samples cured with DU, Opt., and Valo LCUs, respectively. DC% values of the 4 mm samples were 50.4, 44.6, and 38.2 for DU, Opt, and Valo, respectively. SMH values were Valo, OptBased on the results, it can be concluded that curing device and protocol strongly affect crosslinking reactions and thus DC%, SMH, compressive modulus and strain at break values. Consequently, it can be deduced that curing protocol is possibly the most important parameter for microstructure formation of highly-filled composite restoratives because it may bring some structural defects and physical frailties on restorations due to lower degree of polymerization.

  19. Integrating Limiting-Factors Analysis with Process-Based Restoration to Improve Recovery of Endangered Salmonids in the Pacific Northwest, USA

    Directory of Open Access Journals (Sweden)

    Derek B. Booth

    2016-04-01

    Full Text Available Two approaches to ecological restoration planning, limiting-factors analysis and process-based restoration, are employed in efforts to recover endangered salmonid species throughout the Pacific Northwest of North America. Limiting-factors analysis seeks to identify physical limitations to fish production that may be addressed by habitat restoration; it is known as the “Field of Dreams” hypothesis (i.e., if you build it, they will come. Process-based restoration, in contrast, assumes that protection and/or restoration of watershed-scale processes will best achieve self-sustaining habitat features that support salmon populations. Two case studies from the Columbia River basin (northwestern USA display current efforts to integrate these two restoration approaches to improve salmonid populations. Although these examples both identify site-specific habitat features to construct, they also recognize the importance of supporting key watershed processes to achieve restoration goals. The challenge in advancing the practice of restoration planning is not in simply acknowledging the conceptual benefits of process-based restoration while maintaining a traditional focus on enumerating site-specific conditions and identifying habitat-construction projects, but rather in following process-based guidance during recovery planning and, ultimately, through implementation of on-the-ground actions. We encourage a realignment of the restoration community to truly embrace a process-based, multi-scalar view of the riverine landscape.

  20. A Phenomenological Study of the Experience of Respondents in Campus-Based Restorative Justice Programs

    Science.gov (United States)

    Meagher, Peter J.

    2009-01-01

    The focus of this dissertation was the use of restorative justice practices in the collegiate setting. Some have expressed concern with the legal nature of campus conduct processes. Restorative practices have been implemented in criminal justice and K-12 settings and are seen by some as an antidote to overly legalistic campus conduct processes.…

  1. A Dynamic Programming based method for optimizing power system restoration with high wind power penetration

    DEFF Research Database (Denmark)

    Hu, Rui; Hu, Weihao; Li, Pengfei

    2016-01-01

    Power system restoration is very significant for the operation reliability. Although a totally blackout in today's power system rarely happens, the operators still have to make the restoration strategies in advance by using their experience or some strategy supportive systems. Nowadays, as distri...... System. The testing system was modified by replacing traditional generators with wind farms to create a high wind penetration system....... and relatively low cost. Thus, many countries are increasing the wind power penetration in their power system step by step, such as Denmark, Spain and Germany. The incremental wind power penetration brings a lot of new issues in operation and programming. The power system sometimes will operate close to its...... stable limits. Once the blackout happens, a well-designed restoration strategy is significant. This paper focuses on how to ameliorate the power system restoration procedures to adapt the high wind power penetration and how to take full advantages of the wind power plants during the restoration...

  2. Bulk-filled posterior resin restorations based on stress-decreasing resin technology

    DEFF Research Database (Denmark)

    van Dijken, Jan W.V.; Pallesen, Ulla

    2017-01-01

    This randomized study evaluated a flowable resin composite bulk-fill technique in posterior restorations and compared it intraindividually with a conventional 2-mm resin composite layering technique over a 6-yr follow-up period. Thirty-eight pairs of Class II restorations and 15 pairs of Class I...... restorations were placed in 38 adults. In all cavities a single-step self-etch adhesive (Xeno V) was applied. In the first cavity of each pair, the flowable resin composite (SDR) was placed, in bulk increments of up to 4 mm. The occlusal part was completed with a layer of nanohybrid resin composite (Ceram X...... mono). In the second cavity of each pair, the hybrid resin composite was placed in 2-mm increments. The restorations were evaluated using slightly modified US Public Health Service (USPHS) criteria at baseline and then annually for a time period of 6 yr. After 6 yr, 72 Class II restorations and 26...

  3. Resilient architecture design for voltage variation

    CERN Document Server

    Reddi, Vijay Janapa

    2013-01-01

    Shrinking feature size and diminishing supply voltage are making circuits sensitive to supply voltage fluctuations within the microprocessor, caused by normal workload activity changes. If left unattended, voltage fluctuations can lead to timing violations or even transistor lifetime issues that degrade processor robustness. Mechanisms that learn to tolerate, avoid, and eliminate voltage fluctuations based on program and microarchitectural events can help steer the processor clear of danger, thus enabling tighter voltage margins that improve performance or lower power consumption. We describe

  4. A survey of pediatric dentists' caries-related treatment decisions and restorative modalities - A web-based survey.

    Science.gov (United States)

    Halawany, Hassan S; Salama, Fouad; Jacob, Vimal; Abraham, Nimmi Biju; Moharib, Tarfa Nasser Bin; Alazmah, Abdulfatah Samih; Al Harbi, Jawaher Abdulaziz

    2017-04-01

    To identify current practices and the preferred caries-related treatment decisions and restorative modalities of primary teeth among pediatric dental practitioners in Saudi Arabia. This was a web-based cross-sectional survey conducted among licensed pediatric dental practitioners in Saudi Arabia. Following the retrieval of the email addresses from the Saudi Dental Council, an email explaining the purpose of the study and a link to SurveyMonkey electronic survey consisting of 23 questions was sent to all the members registered under the pediatric dentistry practitioners, starting in September till December 2013. The data obtained was analyzed using descriptive statistics and chi square with and without tabulation processes. The level of significance was set at p  restorative option for carious vital anterior primary teeth. About 40% reported doing pulpectomy and restored with composite strip crowns at all times. About 86% of the respondents reported doing pulpotomy and stainless steel crown for restoring carious vital posterior primary teeth whereas 73.8% reported restoring with composite resin. However, 83.1% of the respondents reported that they never used pre-veneered or Zirconia crowns after pulpotomy for restoring carious vital posterior primary teeth. A significantly higher number of male participants reported that they used esthetic pediatric crowns in their practice compared to female participants ( p  restore primary teeth was higher compared to glass ionomer cements and amalgam whereas a limited use of esthetic pediatric crowns was found among the sample surveyed. Esthetic pediatric crowns were more utilized by male compared to female participants.

  5. Postoperative hypersensitivity in class I resin-based composite restorations in general practice: interim results.

    Science.gov (United States)

    Berkowitz, Gary S; Horowitz, Allan J; Curro, Fredrick A; Craig, Ronald G; Ship, Jonathan A; Vena, Donald; Thompson, Van P

    2009-01-01

    Posterior permanent teeth with carious lesions radiographically extending no further than halfway into dentin (N = 565) were restored by 38 dentists in a practice-based research network, using a resin-based composite. Preoperative and 1-, 4-, and 13-week posttreatment hypersensitivity was recorded with an 11-point visual analog scale that was completed anonymously by participants. The analyses determined whether any correlation or association existed among several variables, including degree of carious activity; cavity extent; application of antimicrobial or desensitizing agents; application of liner, dentin-bonding agent and resin-based composite employed; and composite placement method. Three results were fairly unexpected: Only 36% of lesions were ranked as caries-active, 31% of teeth had appreciable preoperative hypersensitivity, and 16% of teeth with no preoperative hypersensitivity had appreciable hypersensitivity at 1 week posttreatment. Preoperative hypersensitivity was correlated with lesion visibility on radiographs but not with dentin caries activity (ranked on opening enamel), preparation depth, or preparation volume. Accrual to the study continues, and conclusions regarding other relationships await 13-week results.

  6. Survival rates of porcelain laminate restoration based on different incisal preparation designs: An analysis

    Science.gov (United States)

    Shetty, Ashish; Kaiwar, Anjali; Shubhashini, N; Ashwini, P; Naveen, DN; Adarsha, MS; Shetty, Mitha; Meena, N

    2011-01-01

    Background: Veneer restorations provide a valid conservative alternative to complete coverage as they avoid aggressive dental preparation; thus, maintaining tooth structure. Initially, laminates were placed on the unprepared tooth surface. Although there is as yet no consensus as to whether or not teeth should be prepared for laminate veneers, currently, more conservative preparations have been advocated. Because of their esthetic appeal, biocompatibility and adherence to the physiology of minimal-invasive dentistry, porcelain laminate veneers have now become a restoration of choice. Currently, there is a lack of clinical consensus regarding the type of design preferred for laminates. Widely varying survival rates and methods for its estimation have been reported for porcelain veneers over approximately 2–10 years. Relatively few studies have been reported in the literature that use survival estimates, which allow for valid study comparisons between the types of preparation designs used. No survival analysis has been undertaken for the designs used. The purpose of this article is to attempt to review the survival rates of veneers based on different incisal preparation designs from both clinical and non-clinical studies. Aims and Objectives: The purpose of this study is to review both clinical and non-clinical studies to determine the survival rates of veneers based on different incisal preparation designs. A further objective of the study is to understand which is the most successful design in terms of preparation. Materials and Methods This study evaluated the existing literature – survival rates of veneers based on incisal preparation designs. The search strategy involved MEDLINE, BITTORRENT and other databases. Statistical Analysis Data were tabulated. Because of variability in the follow-up period in different studies, the follow-up period was extrapolated to 10 years in common for all of them. Accordingly, the failure rate was then estimated and The

  7. Survival rates of porcelain laminate restoration based on different incisal preparation designs: An analysis.

    Science.gov (United States)

    Shetty, Ashish; Kaiwar, Anjali; Shubhashini, N; Ashwini, P; Naveen, Dn; Adarsha, Ms; Shetty, Mitha; Meena, N

    2011-01-01

    Veneer restorations provide a valid conservative alternative to complete coverage as they avoid aggressive dental preparation; thus, maintaining tooth structure. Initially, laminates were placed on the unprepared tooth surface. Although there is as yet no consensus as to whether or not teeth should be prepared for laminate veneers, currently, more conservative preparations have been advocated. Because of their esthetic appeal, biocompatibility and adherence to the physiology of minimal-invasive dentistry, porcelain laminate veneers have now become a restoration of choice. Currently, there is a lack of clinical consensus regarding the type of design preferred for laminates. Widely varying survival rates and methods for its estimation have been reported for porcelain veneers over approximately 2-10 years. Relatively few studies have been reported in the literature that use survival estimates, which allow for valid study comparisons between the types of preparation designs used. No survival analysis has been undertaken for the designs used. The purpose of this article is to attempt to review the survival rates of veneers based on different incisal preparation designs from both clinical and non-clinical studies. The purpose of this study is to review both clinical and non-clinical studies to determine the survival rates of veneers based on different incisal preparation designs. A further objective of the study is to understand which is the most successful design in terms of preparation. This study evaluated the existing literature - survival rates of veneers based on incisal preparation designs. The search strategy involved MEDLINE, BITTORRENT and other databases. Data were tabulated. Because of variability in the follow-up period in different studies, the follow-up period was extrapolated to 10 years in common for all of them. Accordingly, the failure rate was then estimated and The weighted mean was computed. The study found that the window preparation was of the

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

    Directory of Open Access Journals (Sweden)

    Lei Chen

    2017-01-01

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

  9. Influence of resin-based composite restoration technique and endodontic access on cuspal deflection and cervical microleakage scores.

    Science.gov (United States)

    El-Helali, Ruaa; Dowling, Adam H; McGinley, Emma Louise; Duncan, Henry F; Fleming, Garry J P

    2013-03-01

    To assess cuspal deflection and cervical microleakage of mesio-occlusal-distal cavities in standardised premolar teeth restored incrementally with resin-based composite (RBC) placed horizontally or obliquely and with endodontic access cavities (with and without gutta percha and epoxy resin sealer obturation). Thirty-two teeth were allocated to four groups (n=8) and RBC restored in eight horizontal (Group A) or oblique increments (Groups B-D) using a quartz-tungsten-halogen light curing unit. The dependent variable for Groups B-D was endodontic access (none (Group B), obturated without (Group C) and with gutta percha and epoxy resin sealer (Group D)). Cuspal deflections were recorded post-irradiation using a twin channel deflection measuring gauge. Following restoration, the teeth were thermocycled, immersed in fuchsin dye, sectioned and examined for cervical microleakage. Tukey's post hoc tests identified a significant decrease in total cuspal deflection for the horizontal (p=0.015) compared with the oblique placement technique. No significant difference in total cuspal deflection was evident between Groups B and D restored teeth (p>0.318) or in cervical microleakage score between Groups A and D (p=0.575). Deformation is proportional to the cubed power of the length of a uniform cantilever beam and although a crude approximation of cuspal deformation, the reduction in the effective cusp length therefore significantly reduced the deflection in the MOD cavities when the horizontal rather than the oblique incremental restoration technique was employed. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Stress Analysis of a Class II MO-Restored Tooth Using a 3D CT-Based Finite Element Model

    Directory of Open Access Journals (Sweden)

    Yiu Pong Chan

    2012-01-01

    Full Text Available A computational method has been developed for stress analysis of a restored tooth so that experimental effort can be minimized. The objectives of this study include (i developing a method to create a 3D FE assembly model for a restored tooth based on CT images and (ii conducting stress analysis of the restored tooth using the 3D FE model established. To build up a solid computational model of a tooth, a method has been proposed to construct a 3D model from 2D CT-scanned images. Facilitated with CAD tools, the 3D tooth model has been virtually incorporated with a Class II MO restoration. The tooth model is triphasic, including the enamel, dentin, and pulp phases. To mimic the natural constraint on the movement of the tooth model, its corresponding mandible model has also been generated. The relative high maximum principal stress values were computed at the surface under loading and in the marginal region of the interface between the restoration and the tooth phases.

  11. The influence of oral bacteria on the surfaces of resin-based dental restorative materials--an in vitro study.

    Science.gov (United States)

    Willershausen, B; Callaway, A; Ernst, C P; Stender, E

    1999-08-01

    Three tooth-coloured, resin-based restorative materials (Charisma, Dyract, and Pertac) were exposed to typical oral bacteria (S. mutans, S. oralis and A. naeslundii) over a period of up to 35 days. The three strains of bacteria all colonised the resin-based materials within a few hours and formed thick bacterial films. Determination of the bacterial glucose consumption and lactate production during the incubation period showed no difference from the controls which contained no resin samples. Following the experimental exposure, the materials were examined by scanning electron microscopy (SEM) for possible surface damage and roughness was measured in a perthometer. Little damage to the resin-based composite material surfaces (Charisma, Pertac) could be observed, whereas the polyacid-modified composite material (Dyract) showed greater damage. There was a significant difference in the resin surface roughness after exposure to S. mutans and to A. naeslundii. The study clearly showed that the bacteria used strongly adhered to the resin-based restorative materials. As a consequence of bacterial colonisation and/or poor oral hygiene, damage to the restorative materials might develop. This suggests the need for dentists to evaluate personal oral hygiene, along with general indications and economic factors, in selecting materials for restorations, since the known anti-bacterial properties of amalgam are considerable.

  12. Low-voltage organic transistors based on solution processed semiconductors and self-assembled monolayer gate dielectrics

    NARCIS (Netherlands)

    Woebkenberg, Paul H.; Ball, James; Kooistra, Floris B.; Hummelen, Jan C.; de Leeuw, Dago M.; Bradley, Donal D. C.; Anthopoulos, Thomas D.

    2008-01-01

    Reduction in the operating voltage of organic transistors is of high importance for successful implementation in low-power electronic applications. Here we report on low-voltage n-channel transistors fabricated employing a combination of soluble organic semiconductors and a self-assembled gate

  13. Probability-based Prevention of Voltage Violation and Momentary Interruption due to Uncertainty of Renewable Energy Resources

    Science.gov (United States)

    Chaitusaney, Surachai; Yokoyama, Akihiko

    Distributed Generation (DG) provides many advantages to distribution systems. However, the presence of DG units usually causes voltage fluctuation in the systems, and even causes voltage violation. A number of researches have paid attention to this issue that is widely known for years. The other fact that is revealed in this paper is momentary electricity interruptions due to the voltage violation. To prevent damages resulting from voltage violation, sensitive loads are normally equipped with over/under-voltage relays. As a result, the more frequent bus voltages violate their limits, the more momentary electricity interruption tends to occur. In this paper, Momentary Average Interruption Event Frequency Index (MAIFIE) is evaluated to study this influence. In addition, uncertainty from renewable resources is integrated into the proposed voltage regulation method by using Probabilistic Load Flow (PLF). For IEEE-34 Bus test system, the numerical examples show that the uncertainty from renewable energy resources causes considerable MAIFIE, and the proposed method for voltage regulation can serve as an effective prevention for this problem.

  14. Dentin bonding performance and interface observation of an MMA-based restorative material.

    Science.gov (United States)

    Shinagawa, Junichi; Inoue, Go; Nikaido, Toru; Ikeda, Masaomi; Sadr, Alireza; Tagami, Junji

    2016-07-30

    The purpose of this study was to evaluate bonding performance and dentin interface acid resistance using a 4-META/MMA-TBB based restorative material (BF) compared to a conventional 4-META/MMA-TBB resin cement (SB), and the effect of sodium fluoride (NaF) addition to the materials. Dentin surfaces were treated with 10% citric acid-3% ferric chloride (10-3) or 4-META containing self-etching primer (TP), followed by application of BF or SB polymer powders with or without NaF, to evaluate microtensile bond strength (µTBS) in six experimental groups; 10-3/SB, 10-3/BF, TP/SB, TP/BF, TP/SB/NaF and TP/BF/NaF. SEM observation of the resin-dentin interface was performed after acid-base challenge to evaluate interfacial dentin resistance to acid attack. TP/BF showed highest µTBS, while NaF polymers decreased µTBS. TP/BF showed funnel-shaped erosion at the interface, however, NaF polymers improved acid resistance of interface. In conclusion, BF demonstrated high µTBSs and low acid-resistance at the interface. NaF addition enhanced acid resistance but decreased µTBS.

  15. Hard- and software of real time simulation tools of Electric Power System for adequate modeling power semiconductors in voltage source convertor based HVDC and FACTS

    Directory of Open Access Journals (Sweden)

    Ufa Ruslan A.

    2014-01-01

    Full Text Available The motivation of the presented research is based on the needs for development of new methods and tools for adequate simulation of Flexible Alternating Current Transmission System (FACTS devices and High Voltage Direct Current Transmission (HVDC system as part of real electric power systems (EPS. For that, a hybrid approach for advanced simulation of the FACTS and HVDC based on Voltage Source is proposed. The presented simulation results of the developed hybrid model of VSC confirm the achievement of the desired properties of the model and the effectiveness of the proposed solutions.

  16. A Consensus-Based Cooperative Control of PEV Battery and PV Active Power Curtailment for Voltage Regulation in Distribution Networks

    DEFF Research Database (Denmark)

    Zeraati, Mehdi; Golshan, Mohamad Esmail Hamedani; Guerrero, Josep M.

    2018-01-01

    The rapid growth of rooftop photovoltaic (PV) arrays installed in residential houses leads to serious voltage quality problems in low voltage distribution networks (LVDNs). In this paper, a combined method using the battery energy management of plug-in electric vehicles (PEVs) and the active power...... curtailment (APC) of PV arrays is proposed to regulate voltage in LVDNs with high penetration level of PV resources. A distributed control strategy composed of two consensus algorithms is used to reach an effective utilization of limited storage capacity of PEV battery considering its power/capacity and state...... of charge (SoC). A consensus control algorithm is also developed to fairly share the required power curtailment among PVs during overvoltage periods. The main objective is to mitigate the voltage rise due to the reverse power flow and to compensate the voltage drop resulting from the peak load. Overall...

  17. Analysis and Design of a DSTATCOM Based on Sliding Mode Control Strategy for Improvement of Voltage Sag in Distribution Systems

    Directory of Open Access Journals (Sweden)

    Ghazanfar Shahgholian

    2016-07-01

    Full Text Available Voltage sag is considered to be the most serious problem of power quality. It is caused by faults in the power system or by the starting of large induction motors. Voltage sag causes about 80% of the power quality problems in power systems. One of the main reasons for voltage sag is short circuit fault, which can be compensated for by a distribution static compensator (DSTATCOM as an efficient and economical flexible AC transmission system (FACTS device. In this paper, compensation of this voltage sag using DSTATCOM is reviewed, in which a sliding mode control (SMC technique is employed. The results of this control system are compared with a P+Resonant control system. It will be shown that this control system is able to compensate the voltage sag over a broader range compared to other common control systems. Simulation results are obtained using PSCAD/EMTDC software and compared to that of a similar method.

  18. Discrimination of Urban Spaces with Different Level of Restorativeness Based on the Original and on a Shorter Version of Hartig et al.’s Perceived Restorativeness Scale

    Science.gov (United States)

    Negrín, Fátima; Hernández-Fernaud, Estefanía; Hess, Stephany; Hernández, Bernardo

    2017-01-01

    Restorativeness is defined as the potential of the environment to re-establish certain cognitive capacities related to human information processing. The most frequently used instrument for evaluating the restorativeness of places is the Perceived Restorativeness Scale, proposed by Hartig et al. (1991). Later on, shorter versions of the Perceived Restorativeness Scale were proposed. The aim of this work is to evaluate the discriminatory capacity of the original and of a shorter Spanish version of the PRS, considering urban settings previously selected for having different level of restorativeness, according to expert’s criteria. The study involved 244 students and used a 3 × 2 mixed experimental design, with two independent variables: Restorativeness of a place (between-subjects), which was manipulated by showing pictures of settings selected with varying levels of restorativeness (high, medium, low), and length of the scale (within-subjects), which was manipulated by asking subjects to fill in both the original and a shorter version of the PRS. The order of presentation of the two scales was counterbalanced. Results show an appropriate reliability for both version of the scale. Items of being-away, fascination, and coherence of the shorter scale correlate more strongly with the corresponding factor of the original scale, compared to the others factors. Both scales produce similar values for the perceived restorativeness of the different places, except for places with low restorativeness. PMID:29062293

  19. Discrimination of Urban Spaces with Different Level of Restorativeness Based on the Original and on a Shorter Version of Hartig et al.’s Perceived Restorativeness Scale

    Directory of Open Access Journals (Sweden)

    Fátima Negrín

    2017-10-01

    Full Text Available Restorativeness is defined as the potential of the environment to re-establish certain cognitive capacities related to human information processing. The most frequently used instrument for evaluating the restorativeness of places is the Perceived Restorativeness Scale, proposed by Hartig et al. (1991. Later on, shorter versions of the Perceived Restorativeness Scale were proposed. The aim of this work is to evaluate the discriminatory capacity of the original and of a shorter Spanish version of the PRS, considering urban settings previously selected for having different level of restorativeness, according to expert’s criteria. The study involved 244 students and used a 3 × 2 mixed experimental design, with two independent variables: Restorativeness of a place (between-subjects, which was manipulated by showing pictures of settings selected with varying levels of restorativeness (high, medium, low, and length of the scale (within-subjects, which was manipulated by asking subjects to fill in both the original and a shorter version of the PRS. The order of presentation of the two scales was counterbalanced. Results show an appropriate reliability for both version of the scale. Items of being-away, fascination, and coherence of the shorter scale correlate more strongly with the corresponding factor of the original scale, compared to the others factors. Both scales produce similar values for the perceived restorativeness of the different places, except for places with low restorativeness.

  20. Reactive power and voltage control based on general quantum genetic algorithms

    DEFF Research Database (Denmark)

    Vlachogiannis, Ioannis (John); Østergaard, Jacob

    2009-01-01

    This paper presents an improved evolutionary algorithm based on quantum computing for optima l steady-state performance of power systems. However, the proposed general quantum genetic algorithm (GQ-GA) can be applied in various combinatorial optimization problems. In this study the GQ-GA determin...

  1. Analysis of the Vibration Spectrum Based on the Input Voltage Spectrum

    DEFF Research Database (Denmark)

    Mathe, Laszlo; Jakobsen, Uffe; Rasmussen, Peter Omand

    2009-01-01

    Pulse width modulation, present in most drives, gives rise to harmonics in the current and this generates radial forces that cause vibrations in the motor shell. This paper derives an analytical expression for the estimation of the spectrum of the radial force in a machine with an air gap, based...

  2. Using place-based curricula to teach about restoring river systems

    Science.gov (United States)

    Zalles, D. R.; Collins, B. D.; Updegrave, C.; Montgomery, D. R.; Colonnese, T. G.; Sheikh, A. J.; Haynie, K.; Johnson, V.; Data Sets; Inquiry in Environmental Restoration Studies (Nsf Geo Project 0808076)

    2010-12-01

    Zalles, Daniel R. (Center for Technology in Learning, SRI International) Collins, Brian D., Updegrave, Cynthia, Montgomery, David R., Colonnese, Thomas G., Sheikh, Amir J., (University of Washington) Haynie, Kathleen., Johnson, Vonda. (Haynie Research and Evaluation) A collaborative team from the University of Washington and SRI International is developing place based curricula about complex river systems. This NSF-funded project, known as Data Sets and Inquiry in Environmental Restoration Studies (DIGERS), is producing and piloting curricula on river systems of the Puget Sound over a two-year period at the University of Washington and at a public high school on an Indian reservation. At the high school, DIGERS is developing for a population of Native American students a geoscience curriculum that is embedded in their culture and bio-physical environment. At the UW, the goal is to teach about rivers as integrated physical, biological, and human systems that are products of their unique geological and human histories. The curriculum addresses the challenge of teaching general principles about rivers in a way that develops students’ capability to develop a more sophisticated understanding of the interplay of attributes that characterize a particular river at a point in time. Undergraduate students also learn about the challenges of trying to "restore" local river environments to some past condition, including the pitfall of over-generalizing the efficacy of human interventions from one river system to another. For the high school curriculum, a web site is being produced that integrates modules of general information about the focal scientific phenomena (e.g., rivers and floodplains; how human activities influence rivers; salmon habitat) and data and inquiry-related skills (e.g., how to reconstruct historical change) with place based historical and contemporary information about a specific river environment: the Snohomish River watershed. This information consists

  3. Biphenyl liquid crystalline epoxy resin as a low-shrinkage resin-based dental restorative nanocomposite.

    Science.gov (United States)

    Hsu, Sheng-Hao; Chen, Rung-Shu; Chang, Yuan-Ling; Chen, Min-Huey; Cheng, Kuo-Chung; Su, Wei-Fang

    2012-11-01

    Low-shrinkage resin-based photocurable liquid crystalline epoxy nanocomposite has been investigated with regard to its application as a dental restoration material. The nanocomposite consists of an organic matrix and an inorganic reinforcing filler. The organic matrix is made of liquid crystalline biphenyl epoxy resin (BP), an epoxy resin consisting of cyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (ECH), the photoinitiator 4-octylphenyl phenyliodonium hexafluoroantimonate and the photosensitizer champhorquinone. The inorganic filler is silica nanoparticles (∼70-100 nm). The nanoparticles were modified by an epoxy silane of γ-glycidoxypropyltrimethoxysilane to be compatible with the organic matrix and to chemically bond with the organic matrix after photo curing. By incorporating the BP liquid crystalline (LC) epoxy resin into conventional ECH epoxy resin, the nanocomposite has improved hardness, flexural modulus, water absorption and coefficient of thermal expansion. Although the incorporation of silica filler may dilute the reinforcing effect of crystalline BP, a high silica filler content (∼42 vol.%) was found to increase the physical and chemical properties of the nanocomposite due to the formation of unique microstructures. The microstructure of nanoparticle embedded layers was observed in the nanocomposite using scanning and transmission electron microscopy. This unique microstructure indicates that the crystalline BP and nanoparticles support each other and result in outstanding mechanical properties. The crystalline BP in the LC epoxy resin-based nanocomposite was partially melted during exothermic photopolymerization, and the resin expanded via an order-to-disorder transition. Thus, the post-gelation shrinkage of the LC epoxy resin-based nanocomposite is greatly reduced, ∼50.6% less than in commercialized methacrylate resin-based composites. This LC epoxy nanocomposite demonstrates good physical and chemical properties and good biocompatibility

  4. Accuracy of single-tooth restorations based on intraoral digital and conventional impressions in patients.

    Science.gov (United States)

    Boeddinghaus, Moritz; Breloer, Eva Sabina; Rehmann, Peter; Wöstmann, Bernd

    2015-11-01

    The purpose of this clinical study was to compare the marginal fit of dental crowns based on three different intraoral digital and one conventional impression methods. Forty-nine teeth of altogether 24 patients were prepared to be treated with full-coverage restorations. Digital impressions were made using three intraoral scanners: Sirona CEREC AC Omnicam (OCam), Heraeus Cara TRIOS and 3M Lava True Definition (TDef). Furthermore, a gypsum model based on a conventional impression (EXA'lence, GC, Tokyo, Japan) was scanned with a standard laboratory scanner (3Shape D700). Based on the dataset obtained, four zirconia copings per tooth were produced. The marginal fit of the copings in the patient's mouth was assessed employing a replica technique. Overall, seven measurement copings did not fit and, therefore, could not be assessed. The marginal gap was 88 μm (68-136 μm) [median/interquartile range] for the TDef, 112 μm (94-149 μm) for the Cara TRIOS, 113 μm (81-157 μm) for the laboratory scanner and 149 μm (114-218 μm) for the OCam. There was a statistically significant difference between the OCam and the other groups (p < 0.05). Within the limitations of this study, it can be concluded that zirconia copings based on intraoral scans and a laboratory scans of a conventional model are comparable to one another with regard to their marginal fit. Regarding the results of this study, the digital intraoral impression can be considered as an alternative to a conventional impression with a consecutive digital workflow when the finish line is clearly visible and it is possible to keep it dry.

  5. Empiric analysis of zero voltage switching in piezoelectric transformer based resonant converters

    DEFF Research Database (Denmark)

    Rødgaard, Martin Schøler; Andersen, Thomas; Andersen, Michael A. E.

    2012-01-01

    Research and development within piezoelectric transformer (PT) based converters are rapidly increasing, as the technology is maturing and starts to prove its capabilities. High power density and high efficiencies are reported and recently several inductor-less converters have emerged [1...... is to derive a simple expression of the maximal obtainable soft switching capability (ZVS factor), for a specific PT design, assuming a matched load. The expression has been derived through series of parametric sweep simulations of the inductor-less half-bridge topology, which revealed that a linearization...

  6. Experience with virtual reality-based technology in teaching restorative dental procedures.

    Science.gov (United States)

    Buchanan, Judith A

    2004-12-01

    This article reports on extensive experience with advanced simulation at the University of Pennsylvania, School of Dental Medicine (UPSDM). Virtual reality-based technology (VRBT) or advanced simulation is currently available for the instruction of dental students in preclinical restorative procedures. UPSDM was one of the first schools in the world to have extensive experience with VRBT technology using an advanced simulation unit (DentSim) from DenX, Ltd. UPSDM's experience consists of several years of research using control and experimental groups, employing students to participate in an investigative project, and using the units for remediation and a supplement to the preclinical laboratory. Currently, all first-year students (Class of 2007 and Class of 2008) are receiving most of their preparative operative training on the VRBT units. UPSDM started with one (beta) version unit in 1998, which was later updated and expanded first to four units and recently to fifteen units. This communication is presenting the studies that were of fundamental importance in making the decision to acquire fifteen units in 2003. The areas of main interest to the SDM concerning this technology were its use in teaching, refreshing, and remediating students in restorative procedures and its effectiveness as a teaching methodology in relation to time, efficiency, and faculty. Several studies with varying parameters were performed at various time points. The limited statistical analysis conducted was not conclusive for all measures, and in some cases the data only suggest areas of possible significance. This is due to the low number of students who could access the limited number of available units and the change of protocols in response to student and faculty input. Overall, the results do suggest, however, that students learn faster, arrive at the same level of performance, accomplish more practice procedures per hour, and request more evaluations per procedure or per hour than in our

  7. Biomechanical testing of a polymer-based biomaterial for the restoration of spinal stability after nucleotomy

    Directory of Open Access Journals (Sweden)

    Kaps Christian

    2009-07-01

    Full Text Available Abstract Background Surgery for disc herniations can be complicated by two major problems: painful degeneration of the spinal segment and re-herniation. Therefore, we examined an absorbable poly-glycolic acid (PGA biomaterial, which was lyophilized with hyaluronic acid (HA, for its utility to (a re-establish spinal stability and to (b seal annulus fibrosus defects. The biomechanical properties range of motion (ROM, neutral zone (NZ and a potential annulus sealing capacity were investigated. Methods Seven bovine, lumbar spinal units were tested in vitro for ROM and NZ in three consecutive stages: (a intact, (b following nucleotomy and (c after insertion of a PGA/HA nucleus-implant. For biomechanical testing, spinal units were mounted on a loading-simulator for spines. In three cycles, axial loading was applied in an excentric mode with 0.5 Nm steps until an applied moment of ± 7.5 Nm was achieved in flexion/extension. ROM and NZ were assessed. These tests were performed without and with annulus sealing by sewing a PGA/HA annulus-implant into the annulus defect. Results Spinal stability was significantly impaired after nucleotomy (p Conclusion PGA/HA biomaterial seems to be well suited for cell-free and cell-based regenerative treatment strategies in spinal surgery. Its abilities to restore spinal stability and potentially close annulus defects open up new vistas for regenerative approaches to treat intervertebral disc degeneration and for preventing implant herniation.

  8. Mammography image restoration based on a radiographic scattering model from a single projection: Experimental study

    Science.gov (United States)

    Kim, Kyuseok; Park, Soyoung; Kim, Guna; Cho, Hyosung; Je, Uikyu; Park, Chulkyu; Lim, Hyunwoo; Lee, Dongyeon; Lee, Hunwoo; Kang, Seokyoon

    2017-03-01

    In conventional mammography, contrast sensitivity remains limited due to the superimposition of breast tissue and scattered X-rays, which induces low visibility of lesions in the breast and, thus, an excessive number of false-positive findings. Several methods, including digital breast tomosynthesis as a multiplanar imaging modality, air-gap and slot techniques for the reduction of scatters, phase-contrast imaging as another image-contrast modality, etc., have been investigated in attempt to overcome these difficulties. However, those techniques typically require a higher imaging dose or special equipment. In this work, as an alternative, we propose a new image restoration method based on a radiographic scattering model in which the intensity of scattered X-rays and the direct transmission function of a given medium are estimated from a single projection by using the dark-channel prior. We implemented the proposed algorithm and performed an experiment to demonstrate its viability. Our results indicate that most of the structures in the examined breast were very discernable even with no adjustment in the display-window level, thus preserving superior image features and edge sharpening.

  9. An individual-based growth and competition model for coastal redwood forest restoration

    Science.gov (United States)

    van Mantgem, Phillip J.; Das, Adrian J.

    2014-01-01

    Thinning treatments to accelerate coastal redwood forest stand development are in wide application, but managers have yet to identify prescriptions that might best promote Sequoia sempervirens (Lamb. ex D. Don) Endl. (redwood) growth. The creation of successful thinning prescriptions would be aided by identifying the underlying mechanisms governing how individual tree growth responds to competitive environments in coastal redwood forests. We created a spatially explicit individual-based model of tree competition and growth parameterized using surveys of upland redwood forests at Redwood National Park, California. We modeled competition for overstory trees (stems ≥ 20 cm stem diameter at breast height, 1.37 m (dbh)) as growth reductions arising from sizes, distances, and species identity of competitor trees. Our model explained up to half of the variation in individual tree growth, suggesting that neighborhood crowding is an important determinant of growth in this forest type. We used our model to simulate the effects of novel thinning prescriptions (e.g., 40% stand basal area removal) for redwood forest restoration, concluding that these treatments could lead to substantial growth releases, particularly for S. sempervirens. The results of this study, along with continued improvements to our model, will help to determine spacing and species composition that best encourage growth.

  10. Restoring method for missing data of spatial structural stress monitoring based on correlation

    Science.gov (United States)

    Zhang, Zeyu; Luo, Yaozhi

    2017-07-01

    Long-term monitoring of spatial structures is of great importance for the full understanding of their performance and safety. The missing part of the monitoring data link will affect the data analysis and safety assessment of the structure. Based on the long-term monitoring data of the steel structure of the Hangzhou Olympic Center Stadium, the correlation between the stress change of the measuring points is studied, and an interpolation method of the missing stress data is proposed. Stress data of correlated measuring points are selected in the 3 months of the season when missing data is required for fitting correlation. Data of daytime and nighttime are fitted separately for interpolation. For a simple linear regression when single point's correlation coefficient is 0.9 or more, the average error of interpolation is about 5%. For multiple linear regression, the interpolation accuracy is not significantly increased after the number of correlated points is more than 6. Stress baseline value of construction step should be calculated before interpolating missing data in the construction stage, and the average error is within 10%. The interpolation error of continuous missing data is slightly larger than that of the discrete missing data. The data missing rate of this method should better not exceed 30%. Finally, a measuring point's missing monitoring data is restored to verify the validity of the method.

  11. 2D Hydrodynamic Based Logic Modeling Tool for River Restoration Decision Analysis: A Quantitative Approach to Project Prioritization

    Science.gov (United States)

    Bandrowski, D.; Lai, Y.; Bradley, N.; Gaeuman, D. A.; Murauskas, J.; Som, N. A.; Martin, A.; Goodman, D.; Alvarez, J.

    2014-12-01

    In the field of river restoration sciences there is a growing need for analytical modeling tools and quantitative processes to help identify and prioritize project sites. 2D hydraulic models have become more common in recent years and with the availability of robust data sets and computing technology, it is now possible to evaluate large river systems at the reach scale. The Trinity River Restoration Program is now analyzing a 40 mile segment of the Trinity River to determine priority and implementation sequencing for its Phase II rehabilitation projects. A comprehensive approach and quantitative tool has recently been developed to analyze this complex river system referred to as: 2D-Hydrodynamic Based Logic Modeling (2D-HBLM). This tool utilizes various hydraulic output parameters combined with biological, ecological, and physical metrics at user-defined spatial scales. These metrics and their associated algorithms are the underpinnings of the 2D-HBLM habitat module used to evaluate geomorphic characteristics, riverine processes, and habitat complexity. The habitat metrics are further integrated into a comprehensive Logic Model framework to perform statistical analyses to assess project prioritization. The Logic Model will analyze various potential project sites by evaluating connectivity using principal component methods. The 2D-HBLM tool will help inform management and decision makers by using a quantitative process to optimize desired response variables with balancing important limiting factors in determining the highest priority locations within the river corridor to implement restoration projects. Effective river restoration prioritization starts with well-crafted goals that identify the biological objectives, address underlying causes of habitat change, and recognizes that social, economic, and land use limiting factors may constrain restoration options (Bechie et. al. 2008). Applying natural resources management actions, like restoration prioritization, is

  12. Simulation and Modelling of Passivity Based Control of PMSM Under Controlled Voltage

    Science.gov (United States)

    Belabbes, Baghdad; Lousdad, Abdelkader; Meroufel, Abdelkader; Larbaoui, Ahmed

    2013-09-01

    The aim of the present paper is the study of the behaviour of passivity based control and difficulties due to synthesis for various operating conditions of a synchronous motor with a permanent magnets. The study takes into account the guarantee of satisfactory static and dynamic performance. It also allows the system to be insensitive to disturbances and uncertainties on the parameters. A number of estimation techniques have been developed to achieve speed and position sensorless permanent magnet synchronous motor (PMSM) drives. Most of them suffer from variation of motor parameters such as the stator resistance, stator inductance and torque constant. Also it is known that conventional linear estimators are not adaptive variations of the operating point in a nonlinear system.

  13. Biogeography-based algorithm for high voltage electrode surface optimization of a single-phase GIS bus terminal

    Directory of Open Access Journals (Sweden)

    Padghan Purushottam

    2014-01-01

    Full Text Available A new method applying the biogeography-based optimization (BBO technique is presented for the optimization of high voltage electrode surfaces. The aim is to obtain the optimization of the electrode shape in order to achieve a uniform field distribution along the surface of the electrode and maintain maximum field stress at minimum value. The principle of the developed optimization technique is described with an axi-symmetric single-phase GIS bus terminal electrode considered as a quarter-ellipse. In this scheme different aspects of the optimization technique are compared by means of semi-infinite line charges and ring charges to compute the electric field with the charge simulation method (CSM. The new Biogeography Based optimized approach helps in achieving a uniform field distribution with a minimum electric stress on the electrode surface and a minimum deviation angle for the otherwise normal stress vector, holding the assignment factor within the assigned range. The deviation angle is the more sensitive indicator of the simulation accuracy .The assignment factor has an impact on simulation accuracy. The combined BBO/CSM algorithm is capable of finding a better-quality solution, better accuracy, better convergence characteristics and computational efficiency.

  14. Remarkable reduction in the threshold voltage of pentacene-based thin film transistors with pentacene/CuPc sandwich configuration

    Directory of Open Access Journals (Sweden)

    Yi Li

    2014-06-01

    Full Text Available This study investigates the remarkable reduction in the threshold voltage (VT of pentacene-based thin film transistors with pentacene/copper phthalocyanine (CuPc sandwich configuration. This reduction is accompanied by increased mobility and lowered sub-threshold slope (S. Sandwich devices coated with a 5 nm layer of CuPc layer are compared with conventional top-contact devices, and results indicate that VT decreased significantly from −20.4 V to −0.2 V, that mobility increased from 0.18 cm2/Vs to 0.51 cm2/Vs, and that S was reduced from 4.1 V/dec to 2.9 V/dec. However, the on/off current ratio remains at 105. This enhanced performance could be attributed to the reduction in charge trap density by the incorporated CuPc layer. Results suggest that this method is simple and effectively generates pentacene-based organic thin film transistors with high mobility and low VT.

  15. A Fault Diagnosis Method of High Voltage Circuit Breaker Based on Moving Contact Motion Trajectory and ELM

    Directory of Open Access Journals (Sweden)

    Weihua Niu

    2016-01-01

    Full Text Available In order to avoid the deficiencies of conventional high voltage circuit breaker mechanical properties detection methods, a new algorithm based on image block matching with diamond search strategy is presented in this paper. The motion of auxiliary mark on the pull rod or shaft is firstly recorded by a high-speed and high-definition digital camera when the circuit breaker is open or close. Then the motion trajectory is acquired through diamond image block matching method. The mechanical parameters, such as travel and open and close velocity, are calculated according to the travel-time curve of the circuit breaker. Finally, evaluation model is constructed taking mechanical parameters characteristic values as inputs of ELM. Comparing to the existing techniques, our method is a noncontact measurement based on computer vision. It is easy and convenient for practical application since it need not any electrical and mechanical connection to the breaker. Another advantage of our method is that it can obtain the line and angle displacement simultaneously. The experiment results on the circuit breaker of 220 kv show that our method is effective for breaker mechanical properties detection.

  16. A Secondary Voltage Control Method for an AC/DC Coupled Transmission System Based on Model Predictive Control

    DEFF Research Database (Denmark)

    Xu, Fengda; Guo, Qinglai; Sun, Hongbin

    2015-01-01

    to keep the voltage of the pilot bus tracking its set point considering the DC system’s transmission schedule change. The approach is inspired by model predictive control (MPC) to compensate for predictable voltage change affected by DC side transmission power flow and the potential capacitor switching......For an AC/DC coupled transmission system, the change of transmission power on the DC lines will significantly influence the AC systems’ voltage. This paper describes a method to coordinated control the reactive power of power plants and shunt capacitors at DC converter stations nearby, in order...

  17. Extended Stable Boundary of LCL-Filtered Grid-Connected Inverter Based on An Improved Grid-Voltage Feedforward Control

    DEFF Research Database (Denmark)

    Lu, Minghui; Xin, Zhen; Wang, Xiongfei

    2016-01-01

    should be designed under one-sixth of sampling frequency. However, the low resonance frequency leads to a comparatively large filter inductance or/and capacitance. To extend the stable boundary to the region above fs/6, this paper proposes a novel voltage feedforward scheme for the LCL-filtered inverter....... Theoretical analysis is then provided to validate its feasibility and stability. Compared to other widely used active damping strategies, no extra sensors are needed because the filter capacitor voltage, which is used for voltage feedforward control, is also sampled for phase-locked loop in this paper...

  18. Voltage Dependence of Supercapacitor Capacitance

    Directory of Open Access Journals (Sweden)

    Szewczyk Arkadiusz

    2016-09-01

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

  19. Quantitative Evaluation by Glucose Diffusion of Microleakage in Aged Calcium Silicate-Based Open-Sandwich Restorations

    Directory of Open Access Journals (Sweden)

    S. Koubi

    2012-01-01

    Full Text Available This study compared the in vitro marginal integrity of open-sandwich restorations based on aged calcium silicate cement versus resin-modified glass ionomer cement. Class II cavities were prepared on 30 extracted human third molars. These teeth were randomly assigned to two groups (=10 to compare a new hydraulic calcium silicate cement designed for restorative dentistry (Biodentine, Septodont, Saint Maur des Fossés, France with a resin-modified glass ionomer cement (Ionolux, Voco, Cuxhaven, Germany in open-sandwich restorations covered with a light-cured composite. Positive (=5 and negative (=5 controls were included. The teeth simultaneously underwent thermocycling and mechanocycling using a fatigue cycling machine (1,440 cycles, 5–55°C; 86,400 cycles, 50 N/cm2. The specimens were then stored in phosphate-buffered saline to simulate aging. After 1 year, the teeth were submitted to glucose diffusion, and the resulting data were analyzed with a nonparametric Mann-Whitney test. The Biodentine group and the Ionolux group presented glucose concentrations of 0.074 ± 0.035 g/L and 0.080 ± 0.032 g/L, respectively. No statistically significant differences were detected between the two groups. Therefore, the calcium silicate-based material performs as well as the resin-modified glass ionomer cement in open-sandwich restorations.

  20. Components of patient satisfaction with a dental restorative visit: results from the Dental Practice-Based Research Network.

    Science.gov (United States)

    Riley, Joseph L; Gordan, Valeria V; Rindal, D Brad; Fellows, Jeffrey L; Qvist, Vibeke; Patel, Sagar; Foy, Pat; Williams, O Dale; Gilbert, Gregg H

    2012-09-01

    The authors conducted a study to identify components of patient satisfaction with restorative dental care and to test the hypothesis that certain dentist, patient and procedure factors are associated with patient satisfaction. Practitioner-investigators (P-Is) from 197 practices in The Dental Practice-Based Research Network (DPBRN) recruited consecutively seen patients who had defective permanent-tooth restorations that were replaced or repaired. At the end of the treatment visit, P-Is asked each participant to complete a satisfaction survey and mail it directly to a DPBRN regional coordinator. Analysis of the results of 5,879 satisfaction surveys revealed three satisfaction components: interpersonal relationship-comfort factors, material choice-value factors and sensory-evaluative factors. Satisfaction was highest among patients who received care in a private practice model, whose restorations were repaired rather than replaced and whose restored teeth were not molars. These data suggest that a patient's judgments of a dentist's skills and quality of care are based on personal interactions with the dentist, the level of comfort the patient perceives while receiving care and any experience of posttreatment sensitivity in the treated tooth. These conclusions have direct implications for management of patient care before, during and after the procedure. By taking a patient-centered approach, dentists should seek to understand how patients evaluate and rate the service provided, thereby enabling themselves to focus on what each patient values most.

  1. Voltage-controlled oxide barriers in organic/hybrid spin valves based on tunneling anisotropic magnetoresistance

    Science.gov (United States)

    Grünewald, M.; Homonnay, N.; Kleinlein, J.; Schmidt, G.

    2014-11-01

    Resistive switching, i.e., the remanent (reversible) change of a device's resistance, is a widely investigated phenomenon as it holds the prospect for realizing high density memory devices. Resistive switching has also been observed in organic semiconductors; however, a clear understanding of the underlying physics could not yet be obtained. Possible options are for example interface effects at the electrodes or the formation and destruction of filaments. Here we present resistive switching in an organic spin valve based on tunneling anisotropic magnetoresistance. Similar to experiments in conventional spin-valve devices with two ferromagnetic electrodes we observe a modulation of the magnetoresistance by the electrical switching. However, as the magnetoresistance effect's origin is unambiguously clear, which is not always the case for effects in conventional structures, it can be exploited to prove that a tunnel barrier exists at the interface between the ferromagnetic oxide electrode and the organic semiconductor. Furthermore our experiments reveal that this barrier is reversibly modified during the switching, which causes both the change in magnetoresistance and total device resistance. Quantitative analysis indicates that the barrier is situated in the oxide layer. A phenomenological model provides a full description of the microscopic processes involved in the resistive switching.

  2. A Cell-to-Cell Battery Equalizer With Zero-Current Switching and Zero-Voltage Gap Based on Quasi-Resonant LC Converter and Boost Converter

    DEFF Research Database (Denmark)

    Shang, Yunlong; Zhang, Chenghui; Cui, Naxin

    2015-01-01

    these difficulties, an innovative direct cell-to-cell battery equalizer based on quasi-resonant LC converter (QRLCC) and boost DC-DC converter (BDDC) is proposed. The QRLCC is employed to gain zero-current switching (ZCS), leading to a reduction of power losses. The BDDC is employed to enhance the equalization......In conventional equalizers, the facts of bulky size and high cost are widespread. Particularly, the zero switching loss and zero-voltage gap (ZVG) between cells are difficult to implement due to the high-frequency hard switching and the voltage drop across power devices. To overcome...... voltage gap for large balancing current and ZVG between cells. Instead of a dedicated equalizer for each cell, only one balancing converter is employed and shared by all cells, reducing the size and implementation cost. Moreover, the equalization current can be regulated as needed by controlling the duty...

  3. Principle and Design of a Single-phase Inverter-Based Grounding System for Neutral-to-ground Voltage Compensation in Distribution Networks

    DEFF Research Database (Denmark)

    Wang, Wen; Yan, Lingjie; Zeng, Xiangjun

    2017-01-01

    Neutral-to-ground overvoltage may occur in non-effectively grounded power systems because of the distributed parameters asymmetry and resonance between Petersen coil and distributed capacitances. Thus, the constraint of neutral-to-ground voltage is critical for the safety of distribution networks....... In this paper, an active grounding system based on single-phase inverter and its control parameter design method is proposed to achieve this objective. Relationship between its output current and neutral-to-ground voltage is derived to explain the principle of neutral-to-ground voltage compensation. Then......, a practical current detection method is proposed to specify the reference of compensated current. A current control method consisting of proportional resonant (PR) and proportional integral (PI) with capacitive current feedback is then proposed to guarantee sufficient output current accuracy and stability...

  4. Voltage Gain Derivation Based on Energy-Balanced Criterion for a Novel Hybrid-Input PV-Wind Power Conversion System

    Directory of Open Access Journals (Sweden)

    Chih-Lung Shen

    2015-01-01

    Full Text Available This paper applies energy-balanced criterion to a novel hybrid-input PV-wind power conversion system (HPWPCS for voltage gain derivation. With the energy-balanced concept, complicated mathematical problems related to voltage gain derivation can be readily resolved. Based on the derived results, it is proven that the proposed HPWPCS is able to process two different kinds of renewable energy resources simultaneously. Even though the HPWPCS includes seven capacitors and three magnetic components, its voltage gain still can be found by the mathematical analysis. In the theoretical derivation, only the energy status of output inductor is dealt with such that complicated derivation procedure is avoided. This analysis method can also be applied to other hybrid green-energy conversion systems. In this paper, a 200 W 50 kHz prototype of HPWPCS is built and examined to verify the mathematical results.

  5. Sensibility of Teeth Having Based versus Non-Based Amalgam Restorations: A Clinical Study.

    Science.gov (United States)

    1983-04-01

    sealers in isotope penetration studies. (36,37) However, Going(23) wrote that cement bases "serve to mechanically block the gross ingress of injurious...characteristic reaction .... and *. .. 27 most changes may be classified as dengenerative in nature ." A series of studies by Landy and Seltzer(100) used high... endodontics , may not be biologically acceptable to the pulp. The problem is made more difficult since the precise mechanism of dentinal sensitivity is not

  6. Low-voltage gallium-indium-zinc-oxide thin film transistors based logic circuits on thin plastic foil: Building blocks for radio frequency identification application

    NARCIS (Netherlands)

    Tripathi, A.K.; Smits, E.C.P.; Putten, J.B.P.H. van der; Neer, M. van; Myny, K.; Nag, M.; Steudel, S.; Vicca, P.; O'Neill, K.; Veenendaal, E. van; Genoe, G.; Heremans, P.; Gelinck, G.H.

    2011-01-01

    In this work a technology to fabricate low-voltage amorphous gallium-indium-zinc oxide thin film transistors (TFTs) based integrated circuits on 25 µm foils is presented. High performance TFTs were fabricated at low processing temperatures (<150 °C) with field effect mobility around 17 cm2 /V s. The

  7. Design of High-Voltage Switch-Mode Power Amplifier Based on Digital-Controlled Hybrid Multilevel Converter

    National Research Council Canada - National Science Library

    Hou, Yanbin; Sun, Wanrong; Ren, Aifeng; Liu, Shuming

    2016-01-01

    ...) and hybrid multilevel converter. Under the control of input signal, cascaded power converters with separate DC sources operate in PSM switch mode to directly generate high-voltage and high-power output...

  8. Optical properties of base dentin ceramics for all-ceramic restorations.

    Science.gov (United States)

    Shiraishi, Takanobu; Wood, Duncan J; Shinozaki, Nobuya; van Noort, Richard

    2011-02-01

    The study was conducted to compare the optical parameters of VM7(®) M-shade base dentin ceramics (VITA, Germany) for all ceramic restorations to the chemical composition across the 3D-MASTER(®) shade system. Three disc samples, 13 mm diameter and 1.4 mm thickness, were produced for each M-shade following the manufacturer's instructions. Each disc was ground and polished to a thickness of 1.0 mm. Spectral light transmittance and reflectance data were recorded in the visible spectrum under the standard illuminant D65 and 2° observer at 10 nm intervals by using a computer-controlled spectrophotometer. Opacity, translucency and opalescence parameters were determined for each sample. (1) Spectral transmittance and reflectance in the short-wavelength range systematically decreased with increasing chroma number (M1, M2, M3) when compared within the same value (lightness) group. (2) Spectral transmittance and reflectance decreased systematically across the whole visible spectrum with increasing value group number when compared within the same chroma group. (3) Analysis of relationship between chemical composition and various optical parameters for all the samples showed the significant contribution of ZrO₂ and Y₂O₃ substances to optical properties of the present material. Systematic variations in optical properties of VM7(®) M-shade base dentin ceramics were observed throughout the 3D-MASTER(®) shade system and were suggested to be caused by the fine structure of the sample which can interfere with shorter wavelengths in the visible spectrum. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  9. Environmental restoration risk-based prioritization work package planning and risk ranking methodology. Revision 2

    Energy Technology Data Exchange (ETDEWEB)

    Dail, J.L.; Nanstad, L.D.; White, R.K.

    1995-06-01

    This document presents the risk-based prioritization methodology developed to evaluate and rank Environmental Restoration (ER) work packages at the five US Department of Energy, Oak Ridge Field Office (DOE-ORO) sites [i.e., Oak Ridge K-25 Site (K-25), Portsmouth Gaseous Diffusion Plant (PORTS), Paducah Gaseous Diffusion Plant (PGDP), Oak Ridge National Laboratory (ORNL), and the Oak Ridge Y-12 Plant (Y-12)], the ER Off-site Program, and Central ER. This prioritization methodology was developed to support the increased rigor and formality of work planning in the overall conduct of operations within the DOE-ORO ER Program. Prioritization is conducted as an integral component of the fiscal ER funding cycle to establish program budget priorities. The purpose of the ER risk-based prioritization methodology is to provide ER management with the tools and processes needed to evaluate, compare, prioritize, and justify fiscal budget decisions for a diverse set of remedial action, decontamination and decommissioning, and waste management activities. The methodology provides the ER Program with a framework for (1) organizing information about identified DOE-ORO environmental problems, (2) generating qualitative assessments of the long- and short-term risks posed by DOE-ORO environmental problems, and (3) evaluating the benefits associated with candidate work packages designed to reduce those risks. Prioritization is conducted to rank ER work packages on the basis of the overall value (e.g., risk reduction, stakeholder confidence) each package provides to the ER Program. Application of the methodology yields individual work package ``scores`` and rankings that are used to develop fiscal budget requests. This document presents the technical basis for the decision support tools and process.

  10. A comparative evaluation of microleakage of restorations using silorane-based dental composite and methacrylate-based dental composites in Class II cavities: An in vitro study

    Directory of Open Access Journals (Sweden)

    Jambai Sampath Kumar Sivakumar

    2016-01-01

    Full Text Available Aim: The aim of this in vitro study was to evaluate and compare the microleakage of restorations using low shrinkage silorane-based dental composite and methacrylate-based dental composites in Class II cavity at the occlusal and gingival margins. Materials and Methods: Sixty mandibular molars were collected and divided into three experimental groups and one negative control group. Class II slot cavity was prepared on the mesial surface. Experimental groups were restored with Group I: silorane-based microhybrid composite, Group II: methacrylate-based nanohybrid composite, and Group III: Methacrylate-based microhybrid composite, respectively. Group IV: negative control. The samples were thermocycled, root apices were sealed with sticky wax and coated with nail varnish except 1 mm around the restoration. This was followed by immersion in 2% Rhodamine-B dye solution under vacuum at room temperature for 24 h. Then, the samples were sectioned longitudinally in the mesiodistal direction and evaluated under stereomicroscope ×40 magnification. Scoring was done according to the depth of dye penetration in to the cavity. Statistical analysis of the data was done. Results: The results were that no statistically significant difference in the microleakage at the occlusal margin for all the restorative materials, whereas at the gingival margin, silorane-based microhybrid composite showed less microleakage than the methacrylate-based nano- and micro-hybrid composites. Conclusion: In general, silorane-based microhybrid composite had less microleakage among the other materials used in this in vitro study.

  11. Improved Turn-On and Operating Voltages in AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes

    Science.gov (United States)

    Hao, Guo-Dong; Taniguchi, Manabu; Tamari, Naoki; Inoue, Shin-ichiro

    2017-10-01

    While good ohmic contact formation has been achieved on both p-GaN and n-AlGaN surfaces, the turn-on and operating voltages of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) remain very high. We find that this critical problem is mainly caused by the large difference between the annealing temperatures required for ohmic contact formation on the p-GaN and high Al-fraction n-AlGaN surfaces. We studied the effects of the high-temperature annealing treatments required for n-ohmic contact formation on the subsequent p-ohmic contact formation process in DUV-LEDs. The results show that post-annealing treatment at high temperature is necessary to form an ohmic contact on n-Al0.7Ga0.3N, but a treatment temperature of 900°C or more could cause severe degradation of the specific contact resistivity and the bulk resistivity of p-GaN. We conclude that 900°C is the optimum temperature to form an ohmic contact on n-Al0.7Ga0.3N in DUV-LEDs, where p-GaN and n-Al0.7Ga0.3N act as the p- and n-ohmic contact layers, respectively. We also found that the specific contact resistivity of p-GaN can be reduced by an additional low-temperature annealing treatment after the high-temperature annealing step; this effect can be attributed to the enhancement of the hole concentration in the p-GaN surface contact region. Finally, DUV-LEDs that emit at 280 nm were fabricated using four different annealing treatments during processing. A considerable reduction in the series resistance and thereby in the operating voltage was confirmed using the annealing process proposed above, consisting of a high-temperature anneal at 900°C followed by a low-temperature anneal at 500°C for 3 min.

  12. Fault Modeling and Testing for Analog Circuits in Complex Space Based on Supply Current and Output Voltage

    Directory of Open Access Journals (Sweden)

    Hongzhi Hu

    2015-01-01

    Full Text Available This paper deals with the modeling of fault for analog circuits. A two-dimensional (2D fault model is first proposed based on collaborative analysis of supply current and output voltage. This model is a family of circle loci on the complex plane, and it simplifies greatly the algorithms for test point selection and potential fault simulations, which are primary difficulties in fault diagnosis of analog circuits. Furthermore, in order to reduce the difficulty of fault location, an improved fault model in three-dimensional (3D complex space is proposed, which achieves a far better fault detection ratio (FDR against measurement error and parametric tolerance. To address the problem of fault masking in both 2D and 3D fault models, this paper proposes an effective design for testability (DFT method. By adding redundant bypassing-components in the circuit under test (CUT, this method achieves excellent fault isolation ratio (FIR in ambiguity group isolation. The efficacy of the proposed model and testing method is validated through experimental results provided in this paper.

  13. Carrier-Based PWM Method to Reduce Common-Mode Voltage of Three-to-Five-Phase Indirect Matrix Converter

    Directory of Open Access Journals (Sweden)

    Rutian Wang

    2016-01-01

    Full Text Available In order to reduce the common-mode voltage (CMV for three-to-five-phase indirect matrix converter (IMC, the CMV with the conventional modulation strategy is analyzed. A novel carrier-based PWM (CBPWM method is proposed in this paper. The zero vectors in the inverter stage are assigned to the rectifier stage, equivalently, which are not considered in the inverter stage. The zero vectors are selected appropriately to ensure that the dc-link is connected to an input phase with the minimum absolute value, so that the larger CMV can be avoided. Then, the modulation signals are derived by the duty ratios, which are used to compare with the only one carrier signal and generate the gate pulses of switches. With the proposed method, the CMV is reduced effectively compared with the conventional modulation strategy. This method is analyzed and researched with a simulation model established by Matlab/Simulink. Simulation results are provided in detail to verify the feasibility and validity of the proposed method.

  14. The voltage-gated sodium channel Nav1.9 is required for inflammation-based urinary bladder dysfunction.

    Science.gov (United States)

    Ritter, Amy M; Martin, William J; Thorneloe, Kevin S

    2009-03-06

    Tetrodotoxin (TTX)-resistant sodium channels are found in small diameter primary sensory neurons and are thought to be important in the maintenance of inflammatory pain. Here we examined bladder urodynamics of Nav1.9 voltage-gated sodium channel knock out (KO) mice, and the contribution of Nav1.9 to the development of inflammation-based bladder dysfunction. Basal urodynamics were not different between wildtype (WT) mice and those lacking Nav1.9. Peripheral nerve recordings from pelvic afferents in Nav1.9 KO mice revealed a lack of sensitization to intravesicularly applied prostaglandin E2 (PGE2). Consistent with this, cyclophosphamide treatment in vivo, which is associated with an enhancement of PGE2 production, evoked a reduction in bladder capacity of WT, but not Nav1.9 KO mice. We conclude that the Nav1.9 sodium channel provides an important link between inflammatory processes and changes in urodynamic properties that occur during urinary bladder inflammation.

  15. Poly(4-Vinylpyridine)-Based Interfacial Passivation to Enhance Voltage and Moisture Stability of Lead Halide Perovskite Solar Cells.

    Science.gov (United States)

    Chaudhary, Bhumika; Kulkarni, Ashish; Jena, Ajay Kumar; Ikegami, Masashi; Udagawa, Yosuke; Kunugita, Hideyuki; Ema, Kazuhiro; Miyasaka, Tsutomu

    2017-06-09

    It is well known that the surface trap states and electronic disorders in the solution-processed CH3 NH3 PbI3 perovskite film affect the solar cell performance significantly and moisture sensitivity of photoactive perovskite material limits its practical applications. Herein, we show the surface modification of a perovskite film with a solution-processable hydrophobic polymer (poly(4-vinylpyridine), PVP), which passivates the undercoordinated lead (Pb) atoms (on the surface of perovskite) by its pyridine Lewis base side chains and thereby eliminates surface-trap states and non-radiative recombination. Moreover, it acts as an electron barrier between the perovskite and hole-transport layer (HTL) to reduce interfacial charge recombination, which led to improvement in open-circuit voltage (Voc ) by 120 to 160 mV whereas the standard cell fabricated in same conditions showed Voc as low as 0.9 V owing to dominating interfacial recombination processes. Consequently, the power conversion efficiency (PCE) increased by 3 to 5 % in the polymer-modified devices (PCE=15 %) with Voc more than 1.05 V and hysteresis-less J-V curves. Advantageously, hydrophobicity of the polymer chain was found to protect the perovskite surface from moisture and improved stability of the non-encapsulated cells, which retained their device performance up to 30 days of exposure to open atmosphere (50 % humidity). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Evidence-based concepts and procedures for bonded inlays and onlays. Part II. Guidelines for cavity preparation and restoration fabrication.

    Science.gov (United States)

    Rocca, Giovanni Tommaso; Rizcalla, Nicolas; Krejci, Ivo; Dietschi, Didier

    2015-01-01

    The second part of this article series presents an evidence-based update of clinical protocols and procedures for cavity preparation and restoration selection for bonded inlays and onlays. More than ever, tissue conservation dictates preparation concepts, even though some minimal dimensions still have to be considered for all restorative materials. In cases of severe bruxism or tooth fragilization, CAD/CAM composite resins or pressed CAD/CAM lithium disilicate glass ceramics are often recommended, although this choice relies mainly on scarce in vitro research as there is still a lack of medium- to long-term clinical evidence. The decision about whether or not to cover a cusp can only be made after a multifactorial analysis, which includes cavity dimensions and the resulting tooth biomechanical status, as well as occlusal and esthetic factors. The clinical impact of the modern treatment concepts that were outlined in the previous article - Dual Bonding (DB)/Immediate Dentin Sealing (IDS), Cavity Design Optimization (CDO), and Cervical Margins Relocation (CMR) - are described in detail in this article and discussed in light of existing clinical and scientific evidence for simpler, more predictable, and more durable results. Despite the wide choice of restorative materials (composite resin or ceramic) and techniques (classical or CAD/CAM), the cavity for an indirect restoration should meet five objective criteria before the impression.

  17. Mechanical Fault Diagnosis of High Voltage Circuit Breakers Based on Variational Mode Decomposition and Multi-Layer Classifier.

    Science.gov (United States)

    Huang, Nantian; Chen, Huaijin; Cai, Guowei; Fang, Lihua; Wang, Yuqiang

    2016-11-10

    Mechanical fault diagnosis of high-voltage circuit breakers (HVCBs) based on vibration signal analysis is one of the most significant issues in improving the reliability and reducing the outage cost for power systems. The limitation of training samples and types of machine faults in HVCBs causes the existing mechanical fault diagnostic methods to recognize new types of machine faults easily without training samples as either a normal condition or a wrong fault type. A new mechanical fault diagnosis method for HVCBs based on variational mode decomposition (VMD) and multi-layer classifier (MLC) is proposed to improve the accuracy of fault diagnosis. First, HVCB vibration signals during operation are measured using an acceleration sensor. Second, a VMD algorithm is used to decompose the vibration signals into several intrinsic mode functions (IMFs). The IMF matrix is divided into submatrices to compute the local singular values (LSV). The maximum singular values of each submatrix are selected as the feature vectors for fault diagnosis. Finally, a MLC composed of two one-class support vector machines (OCSVMs) and a support vector machine (SVM) is constructed to identify the fault type. Two layers of independent OCSVM are adopted to distinguish normal or fault conditions with known or unknown fault types, respectively. On this basis, SVM recognizes the specific fault type. Real diagnostic experiments are conducted with a real SF₆ HVCB with normal and fault states. Three different faults (i.e., jam fault of the iron core, looseness of the base screw, and poor lubrication of the connecting lever) are simulated in a field experiment on a real HVCB to test the feasibility of the proposed method. Results show that the classification accuracy of the new method is superior to other traditional methods.

  18. Mechanical Fault Diagnosis of High Voltage Circuit Breakers Based on Variational Mode Decomposition and Multi-Layer Classifier

    Directory of Open Access Journals (Sweden)

    Nantian Huang

    2016-11-01

    Full Text Available Mechanical fault diagnosis of high-voltage circuit breakers (HVCBs based on vibration signal analysis is one of the most significant issues in improving the reliability and reducing the outage cost for power systems. The limitation of training samples and types of machine faults in HVCBs causes the existing mechanical fault diagnostic methods to recognize new types of machine faults easily without training samples as either a normal condition or a wrong fault type. A new mechanical fault diagnosis method for HVCBs based on variational mode decomposition (VMD and multi-layer classifier (MLC is proposed to improve the accuracy of fault diagnosis. First, HVCB vibration signals during operation are measured using an acceleration sensor. Second, a VMD algorithm is used to decompose the vibration signals into several intrinsic mode functions (IMFs. The IMF matrix is divided into submatrices to compute the local singular values (LSV. The maximum singular values of each submatrix are selected as the feature vectors for fault diagnosis. Finally, a MLC composed of two one-class support vector machines (OCSVMs and a support vector machine (SVM is constructed to identify the fault type. Two layers of independent OCSVM are adopted to distinguish normal or fault conditions with known or unknown fault types, respectively. On this basis, SVM recognizes the specific fault type. Real diagnostic experiments are conducted with a real SF6 HVCB with normal and fault states. Three different faults (i.e., jam fault of the iron core, looseness of the base screw, and poor lubrication of the connecting lever are simulated in a field experiment on a real HVCB to test the feasibility of the proposed method. Results show that the classification accuracy of the new method is superior to other traditional methods.

  19. Comparison of Conductor-Temperature Calculations Based on Different Radial-Position-Temperature Detections for High-Voltage Power Cable

    Directory of Open Access Journals (Sweden)

    Lin Yang

    2018-01-01

    Full Text Available In this paper, the calculation of the conductor temperature is related to the temperature sensor position in high-voltage power cables and four thermal circuits—based on the temperatures of insulation shield, the center of waterproof compound, the aluminum sheath, and the jacket surface are established to calculate the conductor temperature. To examine the effectiveness of conductor temperature calculations, simulation models based on flow characteristics of the air gap between the waterproof compound and the aluminum are built up, and thermocouples are placed at the four radial positions in a 110 kV cross-linked polyethylene (XLPE insulated power cable to measure the temperatures of four positions. In measurements, six cases of current heating test under three laying environments, such as duct, water, and backfilled soil were carried out. Both errors of the conductor temperature calculation and the simulation based on the temperature of insulation shield were significantly smaller than others under all laying environments. It is the uncertainty of the thermal resistivity, together with the difference of the initial temperature of each radial position by the solar radiation, which led to the above results. The thermal capacitance of the air has little impact on errors. The thermal resistance of the air gap is the largest error source. Compromising the temperature-estimation accuracy and the insulation-damage risk, the waterproof compound is the recommended sensor position to improve the accuracy of conductor-temperature calculation. When the thermal resistances were calculated correctly, the aluminum sheath is also the recommended sensor position besides the waterproof compound.

  20. Control of grid integrated voltage source converters under unbalanced conditions: development of an on-line frequency-adaptive virtual flux-based approach

    Energy Technology Data Exchange (ETDEWEB)

    Suul, Jon Are

    2012-03-15

    Three-Phase Voltage Source Converters (VSCs) are finding widespread applications in grid integrated power conversion systems. The control systems of such VSCs are in an increasing number of these applications required to operate during voltage disturbances and unbalanced conditions. Control systems designed for grid side voltagesensor-less operation are at the same time becoming attractive due to the continuous drive for cost reduction and increased reliability of VSCs, but are not commonly applied for operation during unbalanced conditions. Methods for voltage-sensor-less grid synchronization and control of VSCs under unbalanced grid voltage conditions will therefore be the main focus of this Thesis. Estimation methods based on the concept of Virtual Flux, considering the integral of the converter voltage in analogy to the flux of an electric machine, are among the simplest and most well known techniques for achieving voltage-sensor-less grid synchronization. Most of the established techniques for Virtual Flux estimation are, however, either sensitive to grid frequency variations or they are not easily adaptable for operation under unbalanced grid voltage conditions. This Thesis addresses both these issues by proposing a simple approach for Virtual Flux estimation by utilizing a frequency-adaptive filter based on a Second Order Generalized Integrator (SOGI). The proposed approach can be used to achieve on-line frequency-adaptive varieties of conventional strategies for Virtual Flux estimation. The main advantage is, however, that the SOGI-based Virtual Flux estimation can be arranged in a structure that achieves inherent symmetrical component sequence separation under unbalanced conditions. The proposed method for Virtual Flux estimation can be used as a general basis for voltage-sensor-less grid synchronization and control during unbalanced conditions. In this Thesis, the estimated Virtual Flux signals are used to develop a flexible strategy for control of active

  1. Restorative dentistry for children.

    Science.gov (United States)

    Donly, Kevin J

    2013-01-01

    This article discusses contemporary pediatric restorative dentistry. Indications and contraindications for the choice of different restorative materials in different clinical situations, including the risk assessment of the patient, are presented. The specific use of glass ionomer cement or resin-modified glass ionomer cement, resin-based composite, and stainless steel crowns is discussed so that preparation design and restoration placement is understood. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Restoring and Conserving Khasi Forests: A Community-Based REDD Strategy from Northeast India

    Directory of Open Access Journals (Sweden)

    Mark Poffenberger

    2015-12-01

    Full Text Available An initiative to Reduce Emissions from Deforestation and Forest Degradation (REDD was launched in December 2007 at the Bali Conference of Parties (COP to the United Nations Framework Convention on Climate Change (UNFCCC, yet little progress has been made in Asia in developing certified REDD projects, especially those that engage forest-dependent people. According to UNFCCC, REDD is a multilevel activity that involves both national policy and structures, as well as subnational projects involving local communities [1]. While many Asian nations are trying to create frameworks that link the national strategy to sub-national projects, in India this formal integration has yet to take place. As a consequence projects like the Khasi Hills Community REDD+ project fall outside the UNFCCC strategy and operate under voluntary standards (Plan Vivo and markets. The project involves both avoided deforestation and reforestation components. The project is being implemented by a federation of ten Khasi tribal kingdoms, a major ethnolinguistic group in the Indian state of Meghalaya. Project experience may provide guidance regarding actions required to create a more enabling environment for community forest carbon projects in Asia. These findings may better inform the December 2015 21st UNFCCC Conference of Parties in Paris as they again address REDD strategy. The experience of this Khasi Federation [2] in designing and implementing a REDD project has led to the emergence of a modernizing forest management system that is helping to conserve and restore the Khasi’s ancestral forests. Learning from this REDD project also illustrates the barriers that the Khasi communities have faced, including those imposed by national governments, certifiers, and carbon markets, that will likely constrain the expansion and replication of community-based climate initiatives. The author suggests some alternative policies and systems that may enable greater community participation in

  3. The effect of repeated preheating of dimethacrylate and silorane-based composite resins on marginal gap of class V restorations.

    Science.gov (United States)

    Alizadeh Oskoee, Parnian; Pournaghi Azar, Fatemeh; Jafari Navimipour, Elmira; Ebrahimi Chaharom, Mohammad Esmaeel; Naser Alavi, Fereshteh; Salari, Ashkan

    2017-01-01

    Background. One of the problems with composite resin restorations is gap formation at resin‒tooth interface. The present study evaluated the effect of preheating cycles of silorane- and dimethacrylate-based composite resins on gap formation at the gingival margins of Class V restorations. Methods. In this in vitro study, standard Class V cavities were prepared on the buccal surfaces of 48 bovine incisors. For restorative procedure, the samples were randomly divided into 2 groups based on the type of composite resin (group 1: di-methacrylate composite [Filtek Z250]; group 2: silorane composite [Filtek P90]) and each group was randomly divided into 2 subgroups based on the composite temperature (A: room temperature; B: after 40 preheating cycles up to 55°C). Marginal gaps were measured using a stereomicroscope at ×40 and analyzed with two-way ANOVA. Inter- and intra-group comparisons were analyzed with post-hoc Tukey tests. Significance level was defined at P Class V cavities decreased due to preheating of both composite re-sins. Preheating of silorane-based composites can result in the best marginal adaptation.

  4. Risk-based priority scoring for Brookhaven National Laboratory environmental restoration programs

    Energy Technology Data Exchange (ETDEWEB)

    Morris, S.C.; Meinhold, A.F.

    1995-05-01

    This report describes the process of estimating the risk associated with environmental restoration programs under the Brookhaven National Laboratory Office of Environmental Restoration. The process was part of an effort across all Department of Energy facilities to provide a consistent framework to communicate risk information about the facilities to senior managers in the DOE Office of Environmental Management to foster understanding of risk activities across programs. the risk evaluation was a qualitative exercise. Categories considered included: Public health and safety; site personnel safety and health; compliance; mission impact; cost-effective risk management; environmental protection; inherent worker risk; environmental effects of clean-up; and social, cultural, political, and economic impacts.

  5. Superposed Redox Chemistry of Fused Carbon Rings in Cyclooctatetraene-Based Organic Molecules for High-Voltage and High-Capacity Cathodes.

    Science.gov (United States)

    Zhao, Xiaolin; Qiu, Wujie; Ma, Chao; Zhao, Yingqin; Wang, Kaixue; Zhang, Wenqing; Kang, Litao; Liu, Jianjun

    2018-01-24

    Even though many organic cathodes have been developed and have made a significant improvement in energy density and reversibility, some organic materials always generate relatively low voltage and limited discharge capacity because their energy storage mechanism is solely based on redox reactions of limited functional groups [N-O, C═X (X = O, N, S)] linking to aromatic rings. Here, a series of cyclooctatetraene-based (C 8 H 8 ) organic molecules were demonstrated to have electrochemical activity of high-capacity and high-voltage from carbon rings by means of first-principles calculations and electronic structure analysis. Fused molecules of C 8 -C 4 -C 8 (C 16 H 12 ) and C 8 -C 4 -C 8 -C 4 -C 8 (C 24 H 16 ) contain, respectively, four and eight electron-deficient carbons, generating high-capacity by their multiple redox reactions. Our sodiation calculations predict that C 16 H 12 and C 24 H 16 exhibit discharge capacities of 525.3 and 357.2 mA h g -1 at the voltage change from 3.5 to 1.0 V and 3.7 to 1.3 V versus Na + /Na, respectively. Electronic structure analysis reveals that the high voltages are attributed to superposed electron stabilization mechanisms, including double-bond reformation and aromatization from carbon rings. High thermodynamic stability of these C 24 H 16 -based systems strongly suggests feasibility of experimental realization. The present work provides evidence that cyclooctatetraene-based organic molecules fused with the C 4 ring are promising in designing high-capacity and high-voltage organic rechargeable cathodes.

  6. Restoration of digital off-axis Fresnel hologram by exemplar and search based image inpainting with enhanced computing speed

    Science.gov (United States)

    Jiao, A. S. M.; Tsang, P. W. M.; Poon, T.-C.

    2015-08-01

    In this paper, we proposed a method for restoration of heavily damaged digital off-axis Fresnel holograms based on image inpainting. Being different from existing image inpainting algorithms, we have employed Artificial Bee Colony search technique to increase the computation efficiency of the inpainting process, resulting in a reduction of over one order of magnitude in the computation time. Briefly, an exemplar and search based image inpainting technique is applied to fill in the damaged regions in the hologram, with the most similar fringe patterns in the intact areas obtained from Artificial Bee Colony search algorithm. Experimental results reveal that with our proposed method, the pictorial information in heavily damaged holograms can be recovered with good fidelity, as compared with those obtained with the original intact holograms. This is the first time that image inpainting technique is applied on hologram restoration.

  7. Restorative treatment thresholds for occlusal primary caries among dentists in the dental practice-based research network.

    Science.gov (United States)

    Gordan, Valeria V; Bader, James D; Garvan, Cynthia W; Richman, Joshua S; Qvist, Vibeke; Fellows, Jeffrey L; Rindal, D Brad; Gilbert, Gregg H

    2010-02-01

    OBJECTIVES. The authors report on a study aimed at quantifying the carious lesion depths at which dentists intervene surgically for cases of varying caries penetration and caries risk. They also aimed to identify characteristics that are associated with surgical intervention. The investigators surveyed dentists enrolled in a dental practice-based research network who reported performing at least some restorative dentistry. In the survey, dentists were asked to indicate whether they would intervene surgically in a series of cases involving occlusal caries. Each case presentation included a photograph of an occlusal surface displaying typical characteristics of caries penetration and a written description of a patient at a specific level of risk of developing caries. Using logistic regression, the authors analyzed associations between surgical treatment with dentists' and practices' characteristics and patients' caries risk levels. A total of 517 DPBRN practitioner-investigators responded to the questionnaire. Sixty-three percent of the respondents (326 of 517) indicated that in patients at low risk of developing caries, they would surgically restore teeth with lesions located in inner enamel surfaces and 90 percent would surgically restore teeth with lesions located in outer dentin surfaces. Regarding patients with a high risk of developing caries, 77 percent (398 of 517) of the respondents reported that they would surgically restore inner enamel lesions, and 94 percent (486 of 517) reported that they would restore lesions located on the outer dentin surface. Dentists who did not assess caries risk were more likely than dentists who did assess risk to intervene with dentinal lesions (P = .004). Practitioner-investigators who were in solo practice or a private practice with fewer than four dentists were significantly more likely to intervene surgically with enamel lesions than were dentists in large group practices (those with four or more dentists) (P < .001).

  8. A survey of pediatric dentists' caries-related treatment decisions and restorative modalities – A web-based survey

    OpenAIRE

    Hassan S. Halawany; Fouad Salama; Vimal Jacob; Nimmi Biju Abraham; Tarfa Nasser Bin Moharib; Abdulfatah Samih Alazmah; Jawaher Abdulaziz Al Harbi

    2017-01-01

    Objective: To identify current practices and the preferred caries-related treatment decisions and restorative modalities of primary teeth among pediatric dental practitioners in Saudi Arabia. Materials and methods: This was a web-based cross-sectional survey conducted among licensed pediatric dental practitioners in Saudi Arabia. Following the retrieval of the email addresses from the Saudi Dental Council, an email explaining the purpose of the study and a link to SurveyMonkey electronic s...

  9. Installation Restoration Program Stage 2-1 Remedial Investigation. Beale Air Force Base, Marysville, California. Volume 1. Text and Plates

    Science.gov (United States)

    1991-03-29

    ABSTRACT ( Coen n mIvvrsg of new y &V AW n by blad anfbw) As part of the ongoing Installation Restoration Program at Beale Air Force Base, California, 24...detected at the same depths at 0.005 (be- low LOQ), 0.014, 0.006, and 0.21 mg/kg. 1,1,2 trichloro- ethane was detected at 0.009 mg/kg at 48 feet (42

  10. Induced Voltages Ratio-Based Algorithm for Fault Detection, and Faulted Phase and Winding Identification of a Three-Winding Power Transformer

    Directory of Open Access Journals (Sweden)

    Byung Eun Lee

    2014-09-01

    Full Text Available This paper proposes an algorithm for fault detection, faulted phase and winding identification of a three-winding power transformer based on the induced voltages in the electrical power system. The ratio of the induced voltages of the primary-secondary, primary-tertiary and secondary-tertiary windings is the same as the corresponding turns ratio during normal operating conditions, magnetic inrush, and over-excitation. It differs from the turns ratio during an internal fault. For a single phase and a three-phase power transformer with wye-connected windings, the induced voltages of each pair of windings are estimated. For a three-phase power transformer with delta-connected windings, the induced voltage differences are estimated to use the line currents, because the delta winding currents are practically unavailable. Six detectors are suggested for fault detection. An additional three detectors and a rule for faulted phase and winding identification are presented as well. The proposed algorithm can not only detect an internal fault, but also identify the faulted phase and winding of a three-winding power transformer. The various test results with Electromagnetic Transients Program (EMTP-generated data show that the proposed algorithm successfully discriminates internal faults from normal operating conditions including magnetic inrush and over-excitation. This paper concludes by implementing the algorithm into a prototype relay based on a digital signal processor.

  11. Modeling and control of threshold voltage based on pull-in characteristic for micro self-locked switch

    Science.gov (United States)

    Deng, Jufeng; Hao, Yongping; Liu, Shuangjie

    2017-09-01

    Micro self-locked switches (MSS), where execution voltage corresponds to the output signal, are efficient and convenient platforms for sensor applications. The proper functioning of these sensing devices requires driving accurate displacement under execution voltage. In this work, we show how to control the actuating properties of MSSS. This switch comprises microstructures of various shapes with dimensions from 3.5 to 180 μm, which are optimized to encode a desired manufacture deviation by means of mathematical model of threshold voltage. Compared with pull-in voltage, threshold voltage is more easy to control the pull-in instability point by theoretical analysis. With the help of advanced manufacture technology, switch is processed in accordance with the proposed control method. Then, experimental results show that it is better, which have been validated by corresponding experiments. In addition, they can be known from experiments that the manufacturing technology is advanced and feasible, and its high resilience and stably self-locked function can achieve instantaneously sensing.

  12. High Performance, Low Operating Voltage n-Type Organic Field Effect Transistor Based on Inorganic-Organic Bilayer Dielectric System

    Science.gov (United States)

    Dey, A.; Singh, A.; Kalita, A.; Das, D.; Iyer, P. K.

    2016-04-01

    The performance of organic field-effect transistors (OFETs) fabricated utilizing vacuum deposited n-type conjugated molecule N,N’-Dioctadecyl-1,4,5,8-naphthalenetetracarboxylic diimide (NDIOD2) were investigated using single and bilayer dielectric system over a low-cost glass substrate. Single layer device structure consists of Poly (vinyl alcohol) (PVA) as the dielectric material whereas the bilayer systems contain two different device configuration namely aluminum oxide/Poly (vinyl alcohol) (Al2O3/PVA) and aluminum oxide/Poly (methyl mefhacrylate) (Al2O3/PMMA) in order to reduce the operating voltage and improve the device performance. It was observed that the devices with Al2O3/PMMA bilayer dielectric system and top contact aluminum electrodes exhibit excellent n-channel behaviour under vacuum compared to the other two structures with electron mobility value of 0.32 cm2/Vs, threshold voltages ~1.8 V and current on/off ratio ~104, operating under a very low voltage (6 V). These devices demonstrate highly stable electrical behaviour under multiple scans and low threshold voltage instability in vacuum condition even after 7 days than the Al2O3/PVA device structure. This low operating voltage, high performance OTFT device with bilayer dielectric system is expected to have diverse applications in the next generation of OTFT technologies.

  13. Effect of 38% carbamide peroxide on the microleakage of silorane-based versus methacrylate-based composite restorations

    Directory of Open Access Journals (Sweden)

    Sedighe Sadat Hashemi Kamangar

    2014-08-01

    Full Text Available Objectives This study aimed to assess the effect of 38% carbamide peroxide on the microleakage of class V cavities restored with either a silorane-based composite or two methacrylate-based composites. Materials and Methods A total of 96 class V cavities were prepared on the buccal surface of extracted human teeth with both enamel and dentin margins and were randomly assigned into three groups of Filtek P90 (3M-ESPE + P90 system adhesive (3M-ESPE(group A, Filtek Z250 (3M-ESPE + Adper Prompt L-Pop (3M-ESPE(group B and Filtek Z350XT (3M-ESPE + Adper Prompt L-Pop (group C. Half of the teeth were randomly underwent bleaching (38% carbamide peroxide, Day White, Discus Dental, applying for 15 min, twice a day for 14 day while the remaining half (control were not bleached. Dye penetration was measured following immersion in basic fuchsine. Data were statistically analyzed using Kruskal-Wallis and Mann-Whitney U tests at a level of 0.05. Results No significant differences were found between composites in the control groups in enamel (p = 0.171 or dentin (p = 0.094 margins. After bleaching, microleakage of Z250 (in enamel [p = 0.867] or dentin [p = 0.590] margins and Z350 (in enamel [p = 0.445] or dentin [p = 0.591] margins did not change significantly, but the microleakage of P90 significantly increased in both enamel (p = 0.042 and dentin (p = 0.002 margins. Conclusions No significant differences were noted between the bleached and control subgroups of two methacrylate-based composites in enamel or dentin margins. Microleakage of silorane-based composite significantly increased after bleaching.

  14. Image Restoration Based on Statistic PSF Modeling for Improving the Astrometry of Space Debris

    Science.gov (United States)

    Sun, Rongyu; Jia, Peng

    2017-04-01

    Space debris is a special kind of fast-moving, near-Earth objects, and it is also considered to be an interesting topic in time-domain astronomy. Optical survey is the main technique for observing space debris, which contributes much to the studies of space environment. However, due to the motion of registered objects, image degradation is critical in optical space debris observations, as it affects the efficiency of data reduction and lowers the precision of astrometry. Therefore, the image restoration in the form of deconvolution can be applied to improve the data quality and reduction accuracy. To promote the image processing and optimize the reduction, the image degradation across the field of view is modeled statistically with principal component analysis and the efficient mean point-spread function (PSF) is derived from raw images, which is further used in the image restoration. To test the efficiency and reliability, trial observations were made for both low-Earth orbital and high-Earth orbital objects. The positions of all targets were measured using our novel approach and compared with the reference positions. The performance of image restoration employing our estimated PSF was compared with several competitive approaches. The proposed image restoration outperformed the others so that the influence of image degradation was distinctly reduced, which resulted in a higher signal-to-noise ratio and more precise astrometric measurements.

  15. Community-based restoration of desert wetlands: the case of the Colorado River delta

    Science.gov (United States)

    Osvel Hinojosa-Huerta; Mark Briggs; Yamilett Carrillo-Guerroro; Edward P. Glenn; Miriam Lara-Flores; Martha Roman-Rodriguez

    2005-01-01

    Wetland areas have been drastically reduced through the Pacific Flyway and the Sonoran Desert, with severe consequences for avian populations. In the Colorado River delta, wetlands have been reduced by 80 percent due to water management practices in the Colorado River basin. However, excess flows and agricultural drainage water has restored some areas, providing...

  16. How dentists diagnose and treat defective restorations: evidence from the dental practice-based research network

    DEFF Research Database (Denmark)

    Gordan, Valeria V; Garvan, Cynthia W; Richman, Joshua S

    2009-01-01

    not intervene surgically when the restoration in the scenario was amalgam. Dentists participating in a solo or small private practice (SPP) chose surgical intervention more often than dentists participating in large group practices (LGP) or in public health practices (PHP) (p

  17. Demonstration of a 10 V programmable Josephson voltage standard system based on a multi-chip technique

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, T; Sasaki, H; Yamamori, H; Shoji, A [National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568 (Japan)], E-mail: yamada-takahiro@aist.go.jp

    2008-03-01

    We have demonstrated a programmable Josephson voltage standard (PJVS) operation up to 10.84 V using a multi-chip technique. We combined two PJVS chips fabricated using NbN/(TiN{sub x}/NbN){sub 2} junction technology. Each PJVS chip was mounted on a single chip carrier using bonding wire, and the two chip carriers were connected by a simple Cu lead wire, and mounted on a cryocooler. High-precision measurements confirmed flat voltage steps for all 22 cells, with a peak-to-peak variation of 100 nV and wide margins of at least 0.35 mA. We also confirmed the stability of the voltage steps in spite of a temperature and RF frequency variation of {+-} 0.1 K and {+-} 0.1 GHz, respectively.

  18. Microleakage and Micrographic Evaluation of Composite Restorations With Various Bases Over ZOE Layer in Pulpotomized Primary Molars

    Directory of Open Access Journals (Sweden)

    M. Rezamand

    2011-12-01

    Full Text Available Objective: Zinc oxide eugenol (ZOE under composite restorations should be covered with a suitable material in order to prevent the harmful effect of ZOE on the composite. The aim of this in vitro study was to evaluate microleakage of composite restorations in pulpotomized primary molars with different bases for covering the ZOE layer and to assess the distance between different layers.Materials and Methods: Proximo-occlusal cavities were prepared in 78 extracted second primary molars. Carious lesions were removed and pulpotomy was carried out. Zinc oxide eugenol paste was placed in 2-mm thickness. The teeth were randomly divided in 6 groups and restored as follows: 1. Light-cured composite; 2. Resin-modified glass-ionomer and composite resin; 3. Glass-ionomer and composite resin; 4. Light-cured calcium hydroxide and composite resin; 5.Calcium hydroxide and composite resin; 6. Amalgam and composite resin. The restored specimens were thermocycled for 500 cycles (5°C/55°C and microleakage was assessed by dye penetration technique. Three specimens from each group were processed for scanning electron microscope evaluation to determine the distance between the layers. The results were analyzed by Kruskal-Wallis and Dunn tests.Results: Microleakage assessment revealed significant differences between the groups (P=0.04, with the amalgam group exhibiting the lowest microleakage values. In SEM micrographs no significant differences were observed in the distance between ZOE base layers (P=0.94 and base-composite layers (P=0.47; however, the amalgam group had the lowest distances.Conclusion: The use of amalgam over zinc oxide eugenol layer in pulpotomized primary molars decreases microleakage.

  19. Image registration algorithm for high-voltage electric power live line working robot based on binocular vision

    Science.gov (United States)

    Li, Chengqi; Ren, Zhigang; Yang, Bo; An, Qinghao; Yu, Xiangru; Li, Jinping

    2017-12-01

    In the process of dismounting and assembling the drop switch for the high-voltage electric power live line working (EPL2W) robot, one of the key problems is the precision of positioning for manipulators, gripper and the bolts used to fix drop switch. To solve it, we study the binocular vision system theory of the robot and the characteristic of dismounting and assembling drop switch. We propose a coarse-to-fine image registration algorithm based on image correlation, which can improve the positioning precision of manipulators and bolt significantly. The algorithm performs the following three steps: firstly, the target points are marked respectively in the right and left visions, and then the system judges whether the target point in right vision can satisfy the lowest registration accuracy by using the similarity of target points' backgrounds in right and left visions, this is a typical coarse-to-fine strategy; secondly, the system calculates the epipolar line, and then the regional sequence existing matching points is generated according to neighborhood of epipolar line, the optimal matching image is confirmed by calculating the similarity between template image in left vision and the region in regional sequence according to correlation matching; finally, the precise coordinates of target points in right and left visions are calculated according to the optimal matching image. The experiment results indicate that the positioning accuracy of image coordinate is within 2 pixels, the positioning accuracy in the world coordinate system is within 3 mm, the positioning accuracy of binocular vision satisfies the requirement dismounting and assembling the drop switch.

  20. Voltage sags and transient detection and classification using half/one-cycle windowing techniques based on continuous s-transform with neural network

    Science.gov (United States)

    Daud, Kamarulazhar; Abidin, Ahmad Farid; Ismail, Ahmad Puad

    2017-08-01

    This paper was conducted to detect and classify the different power quality disturbance (PQD) using Half and One-Cycle Windowing Technique (WT) based on Continuous S-Transform (CST) and Neural Network (NN). The system using 14 bus bars based on IEEE standard had been designing using MATLAB©/Simulink to provide PQD data. The datum of PQD is analyzed by using WT based on CST to extract features and it characteristics. Besides, the study focused an important issue concerning the identification of PQD selection and detection, the feature and characteristics of two types of signals such as voltage sag and transient signal are obtained. After the feature extraction, the classified process had been done using NN to show the percentage of classification PQD either voltage sags or transients. The analysis show which selection of cycle for windowing technique can provide the smooth detection of PQD and the suitable characteristic to provide the highest percentage of classification of PQD.