Bao, Bo-Cheng; Xu, Jian-Ping; Liu, Zhong
2009-11-01
By establishing the discrete iterative mapping model of a current mode controlled buck-boost converter, this paper studies the mechanism of mode shift and stability control of the buck-boost converter operating in discontinuous conduction mode with a ramp compensation current. With the bifurcation diagram, Lyapunov exponent spectrum, time-domain waveform and parameter space map, the performance of the buck-boost converter circuit utilizing a compensating ramp current has been analysed. The obtained results indicate that the system trajectory is weakly chaotic and strongly intermittent under discontinuous conduction mode. By using ramp compensation, the buck-boost converter can shift from discontinuous conduction mode to continuous conduction mode, and effectively operates in the stable period-one region.
Institute of Scientific and Technical Information of China (English)
Bao Bo-Cheng; Xu Jian-Ping; Liu Zhong
2009-01-01
By establishing the discrete iterative mapping model of a current mode controlled buck-boost converter, this paper studies the mechanism of mode shift and stability control of the buck-boost converter operating in discontinuous conduction mode with a ramp compensation current. With the bifurcation diagram, Lyapunov exponent spectrum, timedomain waveform and parameter space map, the performance of the buck-boost converter circuit utilizing a compensating ramp current has been analysed. The obtained results indicate that the system trajectory is weakly chaotic and strongly intermittent under discontinuous conduction mode. By using ramp compensation, the buck-boost converter can shift from discontinuous conduction mode to continuous conduction mode, and effectively operates in the stable period-one region.
Energy Technology Data Exchange (ETDEWEB)
Carranza, O. [Escuela Superior de Computo, Instituto Politecnico Nacional (Mexico); Garcera, G.; Figueres, E. [Grupo de Sistemas Electronicos Industriales del Departamento de Ingenieria Electronica, Universidad Politecnica de Valencia (Spain); Gonzalez, L.G. [Departamento de Ingenieria Electronica y Comunicaciones, Universidad de los Andes (Venezuela)
2010-08-15
This paper presents a peak current mode control scheme of a boost rectifier with low distortion of the input current for wind power systems based on permanent magnet synchronous generators with variable speed operation. The three-phase boost rectifier is operated in discontinuous conduction mode (DCM), and power factor correction techniques are applied. It is shown that the DCM operation significantly reduces the total harmonic distortion of the currents in the permanent magnet synchronous generator, increasing the power factor of the system, so that the vibrations and mechanical stress of the generator are minimized. The characteristics of the DCM boost rectifier are studied considering: (1) the series resistance of the inductors; (2) the modeling and adjustment of peak current mode control yielding a stable loop; (3) the design of an input filter that reduces the switching noise in the currents of the generator. (author)
Maestri, S; Uicich, G; Gomez Costa, J; Petrocelli, R; CERN. Geneva. TE Department
2010-01-01
Many high-performance power converters at CERN are implemented with thyristors, mostly in CCM (Continuous Conduction Mode) due to their better dynamic response. In DCM (Discontinuous Conduction Mode), the converter reduces its small-signal gain, producing a degraded time response which can lead to instability. Several of these converters use digital regulation, allowing the implementation of complex non- linear control techniques. Therefore, a strategy to control the converters in DCM (Discontinuous Conduction Mode) can be implemented, bearing in mind that their standard operation (sampling time, measured signals, acquisition system) can not be drastically changed. This report presents the implementation of a new method to control line-commutated converters in discontinuous conduction mode (DCM). The method is based on the modfication of the thyristor's ring angle _ using a linear approximation, yielding nearly the same dynamic performance as in continuous conduction mode. The _ring angle is corrected by addi...
Discontinuous Mode Power Supply
Lagadinos, John; Poulos, Ethel
2012-01-01
A document discusses the changes made to a standard push-pull inverter circuit to avoid saturation effects in the main inverter power supply. Typically, in a standard push-pull arrangement, the unsymmetrical primary excitation causes variations in the volt second integral of each half of the excitation cycle that could lead to the establishment of DC flux density in the magnetic core, which could eventually cause saturation of the main inverter transformer. The relocation of the filter reactor normally placed across the output of the power supply solves this problem. The filter reactor was placed in series with the primary circuit of the main inverter transformer, and is presented as impedance against the sudden changes on the input current. The reactor averaged the input current in the primary circuit, avoiding saturation of the main inverter transformer. Since the implementation of the described change, the above problem has not reoccurred, and failures in the main power transistors have been avoided.
Current discontinuities on superconducting cosmic strings
Energy Technology Data Exchange (ETDEWEB)
Troyan, E., E-mail: et@iaaru.astronautiko.org; Vlasov, Yu. V. [Moscow Institute of Physics and Technology (Russian Federation)
2011-07-15
The propagation of current perturbations on superconducting cosmic strings is considered. The conditions for the existence of discontinuities similar to shock waves have been found. The formulas relating the string parameters and the discontinuity propagation speed are derived. The current growth law in a shock wave is deduced. The propagation speeds of shock waves with arbitrary amplitudes are calculated. The reason why there are no shock waves in the case of time-like currents (in the 'electric' regime) is explained; this is attributable to the shock wave instability with respect to perturbations of the string world sheet.
Trapped electromagnetic modes in a waveguide with a small discontinuity
Stupakov, G. V.; Kurennoy, S. S.
1994-01-01
We demonstrate that a small discontinuity (such as an enlargement or a hole) on a smooth waveguide can result in the appearance of trapped modes localized in the vicinity of the discontinuity. The frequencies of these modes lie slightly below the cutoff frequencies of the corresponding propagating modes in the waveguide. We find the distribution of the electromagnetic field in the modes and calculate their damping rate due to a finite conductivity of the walls. The contribution of the trapped modes to the longitudinal impedance is calculated.
Trapped modes in waveguides with many small discontinuities
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S.S. (Physics Department, University of Maryland, College Park, Maryland 20742 (United States))
1995-03-01
It has been demonstrated recently [G. V. Stupakov and S. S. Kurennoy, Phys. Rev. E 49, 794 (1994)] that a single small discontinuity (such as an enlargement or a hole) on a smooth waveguide can result in the appearance of trapped electromagnetic modes with frequencies slightly below the waveguide cutoff frequencies. The present paper studies a similar phenomenon for a waveguide with many small discontinuities, which is a good model for the vacuum chamber of large accelerators. Frequencies of trapped modes and their contributions to the coupling impedance are calculated. The frequencies for the cases of a few discontinuities or a periodic structure coincide well with those from numerical simulations. The trapped modes produce sharp resonance peaks of the coupling impedance near the cutoff frequencies. The magnitude of these peaks, as well as the existence itself of a trapped mode, strongly depends on the distribution of discontinuities, or on the distance between them if a regular array is considered. The impedance in the extreme case can be as large as [ital N][sup 3] times that for a single discontinuity, where [ital N] is the number of discontinuities.
Trapped modes in waveguides with many small discontinuities
Kurennoy, Sergey S.
1995-03-01
It has been demonstrated recently [G. V. Stupakov and S. S. Kurennoy, Phys. Rev. E 49, 794 (1994)] that a single small discontinuity (such as an enlargement or a hole) on a smooth waveguide can result in the appearance of trapped electromagnetic modes with frequencies slightly below the waveguide cutoff frequencies. The present paper studies a similar phenomenon for a waveguide with many small discontinuities, which is a good model for the vacuum chamber of large accelerators. Frequencies of trapped modes and their contributions to the coupling impedance are calculated. The frequencies for the cases of a few discontinuities or a periodic structure coincide well with those from numerical simulations. The trapped modes produce sharp resonance peaks of the coupling impedance near the cutoff frequencies. The magnitude of these peaks, as well as the existence itself of a trapped mode, strongly depends on the distribution of discontinuities, or on the distance between them if a regular array is considered. The impedance in the extreme case can be as large as N3 times that for a single discontinuity, where N is the number of discontinuities.
Tan, Cheng; Liang, Zhi-Shan
2016-03-01
In this paper, based on the fact that the inductors and capacitors are of fractional order in nature, the four-order mathematical model of the fractional order quadratic Boost converter in type I and type II discontinuous conduction mode (DCM) — DCM is established by using fractional calculus theory. Direct current (DC) analysis is conducted by using the DC equivalent model and the transfer functions are derived from the corresponding alternating current (AC) equivalent model. The DCM-DCM regions of type I and type II are obtained and the relations between the regions and the orders are found. The influence of the orders on the performance of the quadratic Boost converter in DCM-DCM is verified by numerical and circuit simulations. Simulation results demonstrate the correctness of the fractional order model and the efficiency of the proposed theoretical analysis.
MODE THEORY OF MULTILAYER WAVEGUIDE STRUCTURE WITH DISCONTINUITIES
Institute of Scientific and Technical Information of China (English)
Zong Weihua; Liang Changhong
2003-01-01
TEn mode (whose electric field is zero in the normal direction of theboundafiesbetween layers) and TMn mode (whose magnetic field is zero in the normal direction of the bound-aries between layers) are defined. Then conditions under which pure TEn (TMn) modes may existin multilayer waveguide structure with discontinuities are presented. E (H) step wavguides, ridgedwavguides, microstrip lines and fin lines all satisfy the conditions, and hold for TEn (TMn) mode.The conventional conclusion that ridged waveguides with inhomogeneous dielectric-slab loading,microstrip lines and fin lines only hold for hybrid modes is revised. Compared with hybrid modes,the number of unknown variations and matching equations is reduced by half for pure TEn (TMn)modes, and the computation cost is decreased dramatically.
Directory of Open Access Journals (Sweden)
Ćalasan Martin P.
2013-01-01
Full Text Available This paper presents mechanical characteristics of Switched Reluctance Motor (SRM when it operates in Discontinuous Conduction Mode (DCM or in Continuous Conduction Mode (CCM, i.e. when the current through the phase coils (windings flows discontinuously or continuously. Firstly, in order to maximize the output power of SRM optimization of its control parameters was performed, such that the peak and RMS values of the current do not exceed the predefined values. The optimal control parameters vs. rotation speed, as well as the corresponding characteristics of torque, power and efficiency. It is shown that with CCM the machine torque (power, at high speed, can be increased.
Voltage Mode-to-Current Mode Transformation
Directory of Open Access Journals (Sweden)
Tejmal S. Rathore
2012-10-01
Full Text Available This paper proposes a procedure for converting a class of Op Amp-, FTFN-, CC- and CFAbased voltage mode circuits to corresponding current mode circuits without requiring any additional circuit elements and finally from Op Amp-based voltage mode circuits to any of the FTFN, CC and CFA current mode circuits. The latter circuits perform better at high frequency than the former ones. The validity of the transformation has been checked on simulated circuits with PSPICE.
Institute of Scientific and Technical Information of China (English)
徐会静; 赵书霞; 高飞; 张钰如; 李雪春; 王友年
2015-01-01
A new type of two-dimensional self-consistent fluid model that couples an equivalent circuit module is used to in-vestigate the mode transition characteristics and hysteresis in hydrogen inductively coupled plasmas at different pressures, by varying the series capacitance of the matching box. The variations of the electron density, temperature, and the cir-cuit electrical properties are presented. As cycling the matching capacitance, at high pressure both the discontinuity and hysteresis appear for the plasma parameters and the transferred impedances of both the inductive and capacitive discharge components, while at low pressure only the discontinuity is seen. The simulations predict that the sheath plays a determi-native role on the presence of discontinuity and hysteresis at high pressure, by influencing the inductive coupling efficiency of applied power. Moreover, the values of the plasma transferred impedances at different pressures are compared, and the larger plasma inductance at low pressure due to less collision frequency, as analyzed, is the reason why the hysteresis is not seen at low pressure, even with a wider sheath. Besides, the behaviors of the coil voltage and current parameters during the mode transitions are investigated. They both increase (decrease) at the E to H (H to E) mode transition, indicating an improved (worsened) inductive power coupling efficiency.
Xu, Hui-Jing; Zhao, Shu-Xia; Fei, Gao; Yu-Ru, Zhang; Xue-Chun, Li; You-Nian, Wang
2015-11-01
A new type of two-dimensional self-consistent fluid model that couples an equivalent circuit module is used to investigate the mode transition characteristics and hysteresis in hydrogen inductively coupled plasmas at different pressures, by varying the series capacitance of the matching box. The variations of the electron density, temperature, and the circuit electrical properties are presented. As cycling the matching capacitance, at high pressure both the discontinuity and hysteresis appear for the plasma parameters and the transferred impedances of both the inductive and capacitive discharge components, while at low pressure only the discontinuity is seen. The simulations predict that the sheath plays a determinative role on the presence of discontinuity and hysteresis at high pressure, by influencing the inductive coupling efficiency of applied power. Moreover, the values of the plasma transferred impedances at different pressures are compared, and the larger plasma inductance at low pressure due to less collision frequency, as analyzed, is the reason why the hysteresis is not seen at low pressure, even with a wider sheath. Besides, the behaviors of the coil voltage and current parameters during the mode transitions are investigated. They both increase (decrease) at the E to H (H to E) mode transition, indicating an improved (worsened) inductive power coupling efficiency. Project supported by the National Natural Science Foundation of China (Grant Nos. 11175034, 11205025, 11305023, and 11075029).
Institute of Scientific and Technical Information of China (English)
谭兴; 阮新波
2014-01-01
The LCC resonant converter operating in the discontinuous current mode (DCM) can realize zero current switching (ZCS) of power switches, therefore it is suitable for high power applications where IGBT are used as power switchers. In previous literatures, the design methods for selecting the converter parameters always need lots of trail-and-error and the converter parameters are only optimized at the full load but not in the entire load range. To solve these problems, this paper gave a straight-forward design method based on a Mode Boundary Map. For DCM LCC resonant converters, this design method does not need trail-and-error and can reduce the circulating current of the resonant inductor in the entire load range. Therefore, it improves the converter’s efficiency in the entire load range. Finally, two 5 kW/50 V prototypes with different converter parameters were built and some comparison experiments were implemented to validate the effectiveness of this design method.%LCC 谐振变换器工作于谐振电感电流断续模式(discontinuous current mode，DCM)能够实现开关管的零电流开关，因而适用于以IGBT作为开关器件的大功率供电场合。现有文献针对该变换器参数的设计方法通常需要反复试凑，而且设计过程主要优化的是变换器的满载效率，并没有考虑全负载范围。为了解决这些问题，该文提出一种基于变换器模式分界图的设计方法。针对DCM模式的LCC谐振变换器，这种设计方法不需反复试凑，设计得到的参数能够使得在全负载范围内谐振回路环流相对较小，变换器效率较高。论文最后以两台输出均为5 kW/50 V，但变换器参数不同的样机进行了对比实验，验证了该设计方法的正确性。
A novel single phase buck PFC converter in discontinuous capacitor voltage mode operation
Institute of Scientific and Technical Information of China (English)
邓超平; 凌志斌; 叶芃生
2003-01-01
A novel single-phase Buck converter for power factor correction is proposed. It features simple control due to the constant duty ratio PWM used. It can obtain unity power factor by selecting a suitable LC filter at its input to force the voltage of capacitor to operate in discontinuous capacitor voltage mode. And by using another resonant LC filter at its output, it can not only eliminate the input current distortion at the vicinity of the zero crossing of the supply but also drastically reduce the 100 Hz output voltage ripple. The validity of analysis is confirmed by simulation results and experimental results.
DEFF Research Database (Denmark)
Qin, Nan; Xu, Zhao
2008-01-01
in the discontinuous conducting mode (DCM). The new wind turbine model with the variable speed control of the PMSG based on duty cycle control of the boost converter has been developed in Matlab Simulink. Simulation studies show that DCM working mode of the boost converter provides more flexibility in controlling...
Iwens, R. P.; Lee, F. C.; Triner, J. E.
1977-01-01
Using discrete time state variable representation, a generalized computer-aided modeling and analysis of dc-dc converters is presented. The methodology provides exact modeling and is applicable to all types of power stages and duty-cycle control, including continuous and discontinuous inductor current operation. Converter stability, transient behavior and audio susceptibility can be analytically evaluated and predicted. The generalized theory of the proposed approach to converter modeling and analysis is presented first, followed by a demonstrative example applying the theory to a constant frequency buck converter operating in continuous and discontinuous inductor current mode. Excellent agreement with laboratory test data has been observed.
Iwens, R. P.; Lee, F. C.; Triner, J. E.
1977-01-01
Using discrete time state variable representation, a generalized computer-aided modeling and analysis of dc-dc converters is presented. The methodology provides exact modeling and is applicable to all types of power stages and duty-cycle control, including continuous and discontinuous inductor current operation. Converter stability, transient behavior and audio susceptibility can be analytically evaluated and predicted. The generalized theory of the proposed approach to converter modeling and analysis is presented first, followed by a demonstrative example applying the theory to a constant frequency buck converter operating in continuous and discontinuous inductor current mode. Excellent agreement with laboratory test data has been observed.
Ramadas, C; Balasubramaniam, Krishnan; Joshi, M; Krishnamurthy, C V
2011-07-01
In the present work, the interaction of the fundamental anti-symmetric guided Lamb mode (A(o)) with a structural discontinuity in a composite structure was studied through Finite Element numerical simulations and experiments. The structural component selected for this study was a T-joint section made from glass/epoxy material. This co-cured composite structure is made-up of an upper shell (skin) and a spar as the sub-components. It was observed that when A(o) mode interacts with the junction (structural discontinuity) of these sub-components, a mode-converted S(o) mode is generated. Experiments were conducted using air-coupled ultrasound to validate the numerical simulations. The back-propagating "Turning modes", which propagate from the thin region to the spar web and vice versa, were also numerically simulated and experimentally verified.
Cuk, S.; Middlebrook, R. D.
1977-01-01
A method for modelling switching converters in the discontinuous conduction mode is developed, whose starting point is the unified state-space representation, and whose end result is a complete linear circuit model which correctly represents all essential features, namely, the input, output, and transfer properties (static dc as well as dynamic ac small signal). While the method is generally applicable to any switching converter operating in the discontinuous conduction mode, it is extensively illustrated for the three common power stages (buck, boost, and buck-boost). The results for these converters are then easily tabulated owing to the fixed equivalent circuit topology of their canonical circuit model.
Zhang, X.; Burgstaller, R.; Lai, X.; Gehrer, A.; Kefalas, A.; Pang, Y.
2016-11-01
The performance discontinuity of a pump-turbine under pumping mode is harmful to stable operation of units in hydropower station. In this paper, the performance discontinuity phenomenon of the pump-turbine was studied by means of experiment and numerical simulation. In the experiment, characteristics of the pump-turbine with different diffuser vane openings were tested in order to investigate the effect of pumping casing to the performance discontinuity. While other effects such as flow separation and rotating stall are known to have an effect on the discontinuity, the present studied test cases show that prerotation is the dominating effect for the instability, positions of the positive slope of characteristics are almost the same in different diffuser vane opening conditions. The impeller has principal effect to the performance discontinuity. In the numerical simulation, CFD analysis of tested pump-turbine has been done with k-ω and SST turbulence model. It is found that the position of performance curve discontinuity corresponds to flow recirculation at impeller inlet. Flow recirculation at impeller inlet is the cause of the discontinuity of characteristics curve. It is also found that the operating condition of occurrence of flow recirculation at impeller inlet is misestimated with k-ω and SST turbulence model. Furthermore, the original SST model has been modified. We predict the occurrence position of flow recirculation at impeller inlet correctly with the modified SST turbulence model, and it also can improve the prediction accuracy of the pump- turbine performance at the same time.
Energy Technology Data Exchange (ETDEWEB)
Park, Jae Seok [Doosan Heavy Industries and Construction, Changwon (Korea, Republic of); Jang, Chang Heui [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Lee, Jong Po [ANSCO Corp., Daejeon (Korea, Republic of)
2010-06-15
Based on the idea of eigen-mode expansion, a method to analyze the reflection of Lamb wave from a finite vertical discontinuity of plate is theoretically derived and verified by experiment. The theoretical prediction is in good agreement with the experimental result, and this strongly suggests that eigen-mode expansion method could be used for solution of inverse scattering problem for ultrasonic testing using Lamb wave
2017-07-01
strength between 190 to 240 MPa and is broadly characterized as a reactive powder concrete (RPC). RPCs have fine aggregates and powders but do not...ER D C/ G SL T R- 17 -1 9 Performance Assessment of Discontinuous Fibers in Fiber-Reinforced Concrete : Current State-of-the-Art G eo te...Discontinuous Fibers in Ultra-High Performance Fiber-Reinforced Concrete : Current State-of-the-Art Charles A. Burchfield Geotechnical and
DISCONTINUOUS FLOW OF TURBID DENSITY CURRENTS Ⅱ. INTERNAL HYDRAULIC JUMP
Institute of Scientific and Technical Information of China (English)
Jiahua FAN
2005-01-01
Traveling and stationary internal hydraulic jumps in density currents with positive or negative entrainment coefficients were analyzed based on simple assumptions. An expression of internal hydraulic jumps with entrainment coefficients was derived. Experimental data, published in literature, of stationary internal hydraulic jumps in turbid, thermal and saline density currents including measured values of water entrainment were used to compare with theory. Comparison was also made of traveling internal hydraulic jumps between measured data and theory.
Indian Academy of Sciences (India)
Challa Mohana Krishna; Saritha B; Narayanan G
2015-10-01
This paper discusses dynamic modeling of non-isolated DC–DC converters (buck, boost and buck–boost) under continuous and discontinuous modes of operation. Three types of models are presented for each converter, namely, switching model, average model and harmonic model. These models include significant nonidealities of the converters. The switching model gives the instantaneous currents and voltages of the converter. The average model provides the ripple-free currents and voltages, averaged over a switching cycle. The harmonic model gives the peak to peak values of ripple in currents and voltages. The validity of all these models is established by comparing the simulation results with the experimental results from laboratory prototypes, at different steady state and transient conditions. Simulation based on a combination of average and harmonic models is shown to provide all relevant information as obtained from the switching model, while consuming less computation time than the latter.
Discontinuous conduction mode analysis of phase-modulated series resonant converter
Indian Academy of Sciences (India)
UTSAB KUNDU; PARTHASARATHI SENSARMA
2017-08-01
This paper proposes an analytical approach to derive voltage gain for phase-modulated dc–dc series resonant converter (SRC) operating in discontinuous conduction mode (DCM). The conventional fundamental harmonic approximation technique is extended for a non-ideal series resonant tank to clarify the limitations of SRC operating in continuous conduction mode (CCM). The DCM analysis is described in a normalized form defining appropriate base quantities. The converter is analysed both in time and frequency domain to derive a non-linear algebraic function of diode rectifier extinction angle. The root of this function is numericallydetermined using MATLAB and used to predict the dc bus voltage. Analytical derivation of critical load resistance is discussed, which indicates the CCM–DCM boundary condition. Experimental results are presented to validate the analysis
A CMOS current-mode operational amplifier
DEFF Research Database (Denmark)
Kaulberg, Thomas
1993-01-01
A fully differential-input, differential-output, current-mode operational amplifier (COA) is described. The amplifier utilizes three second-generation current conveyors (CCIIs) as the basic building blocks. It can be configured to provide either a constant gain-bandwidth product in a fully balanced...... current-mode feedback amplifier or a constant bandwidth in a transimpedance feedback amplifier. The amplifier is found to have a gain-bandwidth product of 3 MHz, an offset current of 0.8 μA (signal range ±700 μA), and a (theoretically) unlimited slew rate. The amplifier is realized in a standard CMOS 2...
CMOS Current-mode Operational Amplifier
DEFF Research Database (Denmark)
Kaulberg, Thomas
1992-01-01
A fully differential-input differential-output current-mode operational amplifier (COA) is described. The amplifier utilizes three second generation current-conveyors (CCII) as the basic building blocks. It can be configured to provide either a constant gain-bandwidth product in a fully balanced...... current-mode feedback amplifier or a constant bandwidth in a transimpedance feedback amplifier. The amplifier is found to have a gain bandwidth product of 8 MHz, an offset current of 0.8 Â¿A (signal-range Â±700Â¿A) and a (theoretically) unlimited slew-rate. The amplifier is realized in a standard CMOS 2...
Current barriers to confine high frequency common mode currents
Moonen, Dominicus Johannes Guilielmus; Buesink, Frederik Johannes Karel; Leferink, Frank Bernardus Johannes
2016-01-01
A commercially produced three phase power line filter is submitted to a Current Barrier (CB) Electro-Magnetic Compatibility (EMC) zoning strategy as an attempt to confine high frequency common mode currents. The intent of the paper is not to show how to build a ’perfect’ filter, since this is known.
Programmable Current-Mode Universal Active Filters Employing Current Conveyors
Muhammad Taher Abuelma'atti
1998-01-01
Novel current-mode active filter circuits using current-conveyors are presented. The proposed circuits can realize all standard second-order filter functions. The circuits enjoy high output impedances and can, therefore, be easily cascaded to produce higher order filters. Moreover, the realized filter function can be easily programmed using at most a 13-bit digital number without changing the circuit topology.
Current Mode Data Converters for Sensor Systems
DEFF Research Database (Denmark)
Jørgensen, Ivan Herald Holger
This thesis is mainly concerned with data conversion. Especially data conversion using current mode signal processing is treated.A tutorial chapter introducing D/A conversion is presented. In this chapter the effects that cause static and dynamic nonlinearities are discussed along with methods to...
Current-Mode Power Converter for Radiation Control in DBD Excimer Lamps
2012-01-01
A pulsed current-mode converter specifically designed for the supply of dielectric barrier discharge excimer lamps is proposed in this paper. The power supply structure is defined on the basis of causality criteria that are justified by the structure of the lamp model. The converter operation is studied, and its design criteria are established using state-plane analysis. This converter, operating in discontinuous conduction mode, controls directly both the amplitude and the duration of the em...
Analysis of Discharge Spark Energy in Buck Converter of a Continuous Mode of Inductive Current
Institute of Scientific and Technical Information of China (English)
CUI Bao-chun; CHENG Hong; WANG Cong; LU Huan-yu; SHI Yun
2006-01-01
The basic idea of intrinsically safe circuit and the discharge spark in the Buck converter in the explosive atmospheres were introduced. The Buck converter is the main topological structure of the switch type of intrinsically safe circuit, which has two working modes: continuous inductive current (CCM - continuous conduction mode) and discrete inductance current (DCM - discontinuous conduction mode). The operating state of the continuous inductive current mode is analyzed in detail and the energy of discharge spark in various operating modes is discussed. The total energy will decrease with the increase of switch frequency, in a switching cycle; the discharge spark energy has a maximum and a minimum value. Therefore, the Buck converter has smaller discharge spark energy than the linear power circuit and the switch type of intrinsically safe circuit can enhance the output power and the conversion efficiency of the intrinsically safe power.
DEFF Research Database (Denmark)
Gohil, Ghanshyamsinh Vijaysinh; Maheshwari, Ram Krishan; Bede, Lorand;
2015-01-01
for the maximum value of the flux linkage are derived for each of these PWM schemes. In addition, the effect of the proposed PWM scheme on the line current ripple and the switching losses is also analyzed and compared. To verify the analysis, experimental results are presented, which prove the effectiveness......Parallel voltage-source converters (VSCs) require an inductive filter to suppress the circulating current. The size of this filter can be minimized by reducing either the maximum value of the flux linkage or the core losses. This paper presents a modified discontinuous pulsewidth modulation (DPWM......) scheme to reduce the maximum value of the flux linkage and the core losses in the circulating current filter. In the proposed PWM scheme, the dwell time of an active vector is divided within a half-carrier cycle to ensure simultaneous occurrence of the same zero vectors in both VSCs. A function to decide...
Sliding Mode Control of Induction Motor Phase Currents
DEFF Research Database (Denmark)
Hansen, R.B.; Hattel, T.; Bork, J
1995-01-01
Sliding mode control of induction motor phase currents are investigated through development of two control concepts.......Sliding mode control of induction motor phase currents are investigated through development of two control concepts....
Sliding Mode Control of Induction Motor Phase Currents
DEFF Research Database (Denmark)
Hansen, R.B.; Hattel, T.; Bork, J
1995-01-01
Sliding mode control of induction motor phase currents are investigated through development of two control concepts.......Sliding mode control of induction motor phase currents are investigated through development of two control concepts....
MOS Current Mode Logic Near Threshold Circuits
Directory of Open Access Journals (Sweden)
Alexander Shapiro
2014-06-01
Full Text Available Near threshold circuits (NTC are an attractive and promising technology that provides significant power savings with some delay penalty. The combination of NTC technology with MOS current mode logic (MCML is examined in this work. By combining MCML with NTC, the constant power consumption of MCML is reduced to leakage power levels that can be tolerated in certain modern applications. Additionally, the speed of NTC is improved due to the high speed nature of MCML technology. A 14 nm Fin field effect transistor (FinFET technology is used to evaluate these combined circuit techniques. A 32-bit Kogge Stone adder is chosen as a demonstration vehicle for feasibility analysis. MCML with NTC is shown to yield enhanced power efficiency when operated above 1 GHz with a 100% activity factor as compared to standard CMOS. MCML with NTC is more power efficient than standard CMOS beyond 9 GHz over a wide range of activity factors. MCML with NTC also exhibits significantly lower noise levels as compared to standard CMOS. The results of the analysis demonstrate that pairing NTC and MCML is efficient when operating at high frequencies and activity factors.
Institute of Scientific and Technical Information of China (English)
Tong Kang; Zheng-peng Wu; De-hao Yu
2004-01-01
In this paper, we investigate the finite element A - φ method to approximate the eddy current equations with discontinuous coefficients in general three-dimensional Lipschitz polyhedral eddy current region. Nonmatching finite element meshes on the interface are considered and optimal error estimates are obtained.
Directory of Open Access Journals (Sweden)
S. D. Parkinson
2014-05-01
Full Text Available High resolution direct numerical simulations (DNS are an important tool for the detailed analysis of turbidity current dynamics. Models that resolve the vertical structure and turbulence of the flow are typically based upon the Navier–Stokes equations. Two-dimensional simulations are known to produce unrealistic cohesive vortices that are not representative of the real three-dimensional physics. The effect of this phenomena is particularly apparent in the later stages of flow propagation. The ideal solution to this problem is to run the simulation in three dimensions but this is computationally expensive. This paper presents a novel finite-element (FE DNS turbidity current model that has been built within Fluidity, an open source, general purpose, computational fluid dynamics code. The model is validated through re-creation of a lock release density current at a Grashof number of 5 × 106 in two, and three-dimensions. Validation of the model considers the flow energy budget, sedimentation rate, head speed, wall normal velocity profiles and the final deposit. Conservation of energy in particular is found to be a good metric for measuring mesh performance in capturing the range of dynamics. FE models scale well over many thousands of processors and do not impose restrictions on domain shape, but they are computationally expensive. Use of discontinuous discretisations and adaptive unstructured meshing technologies, which reduce the required element count by approximately two orders of magnitude, results in high resolution DNS models of turbidity currents at a fraction of the cost of traditional FE models. The benefits of this technique will enable simulation of turbidity currents in complex and large domains where DNS modelling was previously unachievable.
Energy Technology Data Exchange (ETDEWEB)
Parsapour, Amir, E-mail: amirparsapour@gmail.com [Department of Electrical Engineering, University of Isfahan, Isfahan (Iran, Islamic Republic of); Dehkordi, Behzad Mirzaeian, E-mail: mirzaeian@eng.ui.ac.ir [Department of Electrical Engineering, University of Isfahan, Isfahan (Iran, Islamic Republic of); Moallem, Mehdi, E-mail: moallem@cc.iut.ac.ir [Department of Electrical Engineering, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of)
2015-03-15
In applications in which the high torque per ampere at low speed and rated power at high speed are required, the continuous current method is the best solution. However, there is no report on calculating the core loss of SRM in continuous current mode of operation. Efficiency and iron loss calculation which are complex tasks in case of conventional mode of operation is even more involved in continuous current mode of operation. In this paper, the Switched Reluctance Motor (SRM) is modeled using finite element method and core loss and copper loss of SRM in discontinuous and continuous current modes of operation are calculated using improved analytical techniques to include the minor loop losses in continuous current mode of operation. Motor efficiency versus speed in both operation modes is obtained and compared. - Highlights: • Continuous current method for Switched Reluctance Motor (SRM) is explained. • An improved analytical technique is presented for SRM core loss calculation. • SRM losses in discontinuous and continuous current operation modes are presented. • Effect of mutual inductances on SRM performance is investigated.
Instantaneous Current Feedback Control Strategy on Buck Mode Inverter
Institute of Scientific and Technical Information of China (English)
2011-01-01
Control strategies for Buck mode inverter have important effect on static and dynamic characteristics, reliability, load capacity, and short-circuit resistance. Instantaneous current feedback control strategies include instantaneous inductor current feedback control and instantaneous capacitor current feedback control, both of which have essential difference. When the Buck mode inverter respectively adopts instantaneous inductor current and capacitor current feedback control strategies, characteristics of stability, output voltage and power, short circuit, nonlinear load and dynamic are fully investigated in this paper.
Drift modes of a quasi-two-dimensional current sheet
Energy Technology Data Exchange (ETDEWEB)
Artemyev, A. V.; Malova, Kh. V.; Popov, V. Yu.; Zelenyi, L. M. [Russian Academy of Sciences, Space Research Institute (Russian Federation)
2012-03-15
Stability of a plasma configuration consisting of a thin one-dimensional current sheet embedded into a two-dimensional background current sheet is studied. Drift modes developing in plasma as unstable waves along the current direction are considered. Dispersion relations for kink and sausage perturbation modes are obtained depending on the ratio of parameters of thin and background current sheets. It is shown that the existence of the background sheet results in a decrease in the instability growth rates and a significant increase in the perturbation wavelengths. The role of drift modes in the excitation of oscillations observed in the current sheet of the Earth's magnetotail is discussed.
Bounded Algebra and Current-Mode Digital Circuits
Institute of Scientific and Technical Information of China (English)
WU Xunwei; Massoud Pedram
1999-01-01
This paper proposes two boundedarithmetic operations, which are easily realized with current signals.Based on these two operations, a bounded algebra system suitable fordescribing current-mode digital circuits is developed and itsrelationship with the Boolean algebra, which is suitable for representingvoltage-mode digital circuits, is investigated. Design procedure forcurrent-mode circuits using the proposed algebra system is demonstratedon a number of common circuit elements which are used to realizearithmetic operations, such as adders and multipliers.
Discharge current modes of high power impulse magnetron sputtering
Directory of Open Access Journals (Sweden)
Zhongzhen Wu
2015-09-01
Full Text Available Based on the production and disappearance of ions and electrons in the high power impulse magnetron sputtering plasma near the target, the expression of the discharge current is derived. Depending on the slope, six possible modes are deduced for the discharge current and the feasibility of each mode is discussed. The discharge parameters and target properties are simplified into the discharge voltage, sputtering yield, and ionization energy which mainly affect the discharge plasma. The relationship between these factors and the discharge current modes is also investigated.
Ohmic scaling based on current diffusive ballooning mode
Energy Technology Data Exchange (ETDEWEB)
Yagi, Masatoshi; Itoh, Sanae [Kyushu Univ., Kasuga, Fukuoka (Japan). Research Inst. for Applied Mechanics; Fukuyama, Atsushi; Itoh, Kimitaka
1996-01-01
Based on the anomalous transport model due to current diffusive ballooning mode turbulence, the global energy confinement time in a tokamak with Ohmic heating is theoretically studied. Relations to empirical scaling laws are also discussed. (author)
DOCCⅡ-based electronically tunable current-mode biquadratic filters
Institute of Scientific and Technical Information of China (English)
Wang Weidong
2005-01-01
A complete state variable current-mode biquadratic filter built by duo-output CCⅡ (DOCCⅡ) with variable current gain is presented. All the coefficients of the filter can be independently tuned through the variable current gain factors of the DOCCⅡ. Based on the principles upon which the general biquadratic filter was constructed, a universal electronically tunable current-mode filter is proposed which implements the low-pass, high-pass, band-pass, band-suppress and all-pass second order transfer functions simultaneously. The PSPICE simulations of frequency responses of second-order filter of are also given.
Electronically Tunable Current-Mode Quadrature Oscillator Using Single MCDTA
Directory of Open Access Journals (Sweden)
Y. Li
2010-12-01
Full Text Available This paper presents a modified current differencing transconductance amlpifier (MCDTA and the MCDTA based quadrature oscillator. The oscillator is current-mode and provides current output from high output impedance terminals. The circuit uses only one MCDTA and two grounded capacitors, and is easy to be integrated. Its oscillation frequency can be tuned electronically by tuning bias currents of MCDTA. Finally, frequency error is analyzed. The results of circuit simulations are in agreement with theory.
Prasanna, D; Venkata Mohan, S; Purushotham Reddy, B; Sarma, P N
2008-05-01
Bioremediation of soil-bound anthracene was studied in a series of bio-slurry phase reactors operated in periodic discontinuous/sequencing batch mode under anoxic-aerobic-anoxic microenvironment using native soil microflora. Five reactors were operated for a total cycle period of 144 h (6 days) at soil loading rate of 16.66 kg soil/m(3)/day at 30 +/- 2 degrees C temperature. The performance of the bioreactors was studied at various substrate loading rates (volumetric substrate loading rate (SLR), 0.1, 0.2 and 0.3g anthracene/kg soil/day) with and without bioaugmentation (domestic sewage inoculum; 2 x 10(6) CFU/g of soil). Control reactor (without microflora) showed negligible degradation of anthracene due to the absence of biological activity. The performance of the bio-slurry system with respect to anthracene degradation was found to depend on both substrate loading rate and bioaugmentation. Application of bioaugmentation showed positive influence on the rate of degradation of anthracene. Anthracene degradation data was analysed using different kinetic models to understand the mechanism of bioremediation process in the bio-slurry phase system. Variation in pH/oxidation-reduction potential (ORP), soil microflora and oxygen consumption rate correlated well with the substrate degradation pattern observed during soil slurry phase anthracene degradation.
Distribution Grid Fault Location Applying Transient Zero-mode Current
Directory of Open Access Journals (Sweden)
Yunchuan Zhang
2012-09-01
Full Text Available To aim at the puzzles on faults location in distribution grids, the paper analyzed the distributing characteristics of transient zero-mode currents as the faults occurred, with the aid of correlation theory, a new fault circuit-selection and fault-location method was proposed based on transient zero model current for power distribution grid faults. The method is based on such a fact that the RMS was maximum of fault line transient zero-mode current, and the inner products between it and other line transient zero-mode current were less than zero, in addition, the transient zero-model currents at two sides of the fault point possessed opposite polarity and diverse waveform, and as well as small correlation coefficient closer to zero. In the end, the simulation results show that the proposed method on circuit-selection and fault-location for power distribution grids fault based on transient zero- mode current is correct and effective, and not affected by voltage epoch angle, and grounding resistance, and as well as neutral-point grounding modes.
Wong, R. C.; Owen, H. A., Jr.; Wilson, T. G.
1981-01-01
Small-signal models are derived for the power stage of the voltage step-up (boost) and the current step-up (buck) converters. The modeling covers operation in both the continuous-mmf mode and the discontinuous-mmf mode. The power stage in the regulated current step-up converter on board the Dynamics Explorer Satellite is used as an example to illustrate the procedures in obtaining the small-signal functions characterizing a regulated converter.
Adaptive slope compensation for high bandwidth digital current mode controller
DEFF Research Database (Denmark)
Taeed, Fazel; Nymand, Morten
2015-01-01
An adaptive slope compensation method for digital current mode control of dc-dc converters is proposed in this paper. The compensation slope is used for stabilizing the inner current loop in peak current mode control. In this method, the compensation slope is adapted with the variations...... in converter duty cycle. The adaptive slope compensation provides optimum controller operation in term of bandwidth over wide range of operating points. In this paper operation principle of the controller is discussed. The proposed controller is implemented in an FPGA to control a 100 W buck converter...
Analysis of current diffusive ballooning mode in tokamaks
Energy Technology Data Exchange (ETDEWEB)
Uchida, Morihisa [Faculty of Engineering, Okayama University, Okayama (Japan); Fukuyama, Atsushi [Kyoto Univ. (Japan). Dept. of Nuclear Engineering; Itoh, Kimitaka [National Inst. for Fusion Science, Toki, Gifu (Japan); Itoh, Sanae-I.; Yagi, Masatoshi [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics
2000-07-01
The effect of finite gyroradius on the current diffusive ballooning mode is examined. Starting from the reduced MHD equations including turbulent transports, coupling with drift motion and finite gyroradius effect of ions, we derive a ballooning mode equation with complex transport coefficients. The eigenfrequency, saturation level and thermal diffusivity are evaluated numerically from the marginal stability condition. Preliminary results of their parameter dependence are presented. (author)
Design Considerations for CMOS Current Mode Operational Amplifiers and Current Conveyors
DEFF Research Database (Denmark)
Bruun, Erik
This dissertation is about CMOS current conveyors and current mode operational amplifiers (opamps). They are generic devices for continuous time signal processing in circuits and systems where signals are represented by currents.Substantial advancements are reported in the dissertation, both...... implementations of current mode opamps in CMOS technology are described. Also, current conveyor configurations with multiple outputs and flexible feedback connections from outputs to inputs are introduced. The dissertation includes several examples of circuit configurations ranging from simple class A and class...... AB conveyor implementations to implementations based on purely digital circuit structures and on more complex analog subsystems such as a voltage mode opamp with feedback to provide a voltage follower action. An important by-product of the investigation of current mode structures is the definition...
Nagendranatha Reddy, C; Naresh Kumar, A; Annie Modestra, J; Venkata Mohan, S
2014-08-01
Variation in anoxic microenvironment (multi-phase (MP) metabolic shift strategy) during cycle operation of periodic discontinuous batch/sequencing batch (PDBR/SBR) mode operation showed enhanced degradation of recalcitrant azo dye (C.I. Acid Black 10B) at higher dye load (1250mg/l). The process performance was evaluated by varying anoxic phasing period during cycle operation. Before multiphase (BMP) operation with 2.1% of anoxic period showed color/COD removal efficiency of 41.9%/46.3%. Increment in anoxic period responded favorable in enhancing treatment efficiency [AMPI (16.2%), 49.4%/52.4%; AMPII (26.6%), 54.7%/57.2%; AMPIII (34.9%), 58.4%/61.5%]. Relatively higher bio-electrochemical activity, persistent reductive behavior (redox catalytic currents, 0.26/-0.72μA), prevalence of redox shuttlers (Fe-S proteins, cytochromes, quinones) facilitating enhanced electron transfer by minimization of associated losses and higher enzyme activities were observed with induction of anoxic phase. Anoxic condition shifts system microenvironment between oxidation and reduction assisting reduction of dye to its intermediates followed by their mineralization.
DISCONTINUOUS FLOW OF TURBID DENSITY CURRENTS I. CHANNEL EXPANSION AND CONTRACTION
Institute of Scientific and Technical Information of China (English)
Jiahua FAN
2005-01-01
Laboratory experiments on turbid density currents were conducted to observe the flow features of these currents with abrupt contracted and expanded reaches. Experimental data were used to determine water entrainment coefficients for both channel expansion and contraction. Expressions for turbid density currents with water entrainment coefficients in abrupt contracted and expanded reaches were derived,and compared with experimental data.
Design Considerations for CMOS Current Mode Operational Amplifiers and Current Conveyors
DEFF Research Database (Denmark)
Bruun, Erik
This dissertation is about CMOS current conveyors and current mode operational amplifiers (opamps). They are generic devices for continuous time signal processing in circuits and systems where signals are represented by currents.Substantial advancements are reported in the dissertation, both...... related to circuit implementations and system configurations and to an analysis of the fundamental limitations of the current mode technique.In the field of system configurations and circuit implementations different configurations of high gain current opamps are introduced and some of the first...... implementations of current mode opamps in CMOS technology are described. Also, current conveyor configurations with multiple outputs and flexible feedback connections from outputs to inputs are introduced. The dissertation includes several examples of circuit configurations ranging from simple class A and class...
A Simple Current-Mode Quadrature Oscillator Using Single CDTA
Directory of Open Access Journals (Sweden)
D. Biolek
2008-12-01
Full Text Available This article presents a simple current-mode quadrature oscillator using a single Current Differencing Transconductance Amplifier (CDTA as the active element. The oscillation condition and oscillation frequency can be electronically controlled. The circuit structure is very simple, consisting of merely one CDTA, one resistor and two capacitors. The proposed circuit is suitable for IC architecture. The PSpice simulation and experimental results are shown, and the results agree well with the theoretical assumptions.
Programmable Input Mode Instrumentation Amplifier Using Multiple Output Current Conveyors
Directory of Open Access Journals (Sweden)
Pankiewicz Bogdan
2017-03-01
Full Text Available In this paper a programmable input mode instrumentation amplifier (IA utilising second generation, multiple output current conveyors and transmission gates is presented. Its main advantage is the ability to choose a voltage or current mode of inputs by setting the voltage of two configuration nodes. The presented IA is prepared as an integrated circuit block to be used alone or as a sub-block in a microcontroller or in a field programmable gate array (FPGA, which shall condition analogue signals to be next converted by an analogue-to-digital converter (ADC. IA is designed in AMS 0.35 µm CMOS technology and the power supply is 3.3 V; the power consumption is approximately 9.1 mW. A linear input range in the voltage mode reaches ± 1.68 V or ± 250 µA in current mode. A passband of the IA is above 11 MHz. The amplifier works in class A, so its current supply is almost constant and does not cause noise disturbing nearby working precision analogue circuits.
Directory of Open Access Journals (Sweden)
A. N. Kuzovlev
2014-01-01
Full Text Available Presents investigations on blocking algorithm for transformer current protections during magnetizing inrush current. The investigations have shown that the algorithm has high sensitivity and reliably determines magnetizing inrush current modes.
Current-Driven Switch-Mode Audio Power Amplifiers
DEFF Research Database (Denmark)
Knott, Arnold; Buhl, Niels Christian; Andersen, Michael A. E.
2012-01-01
The conversion of electrical energy into sound waves by electromechanical transducers is proportional to the current through the coil of the transducer. However virtually all audio power amplifiers provide a controlled voltage through the interface to the transducer. This paper is presenting...... a switch-mode audio power amplifier not only providing controlled current but also being supplied by current. This results in an output filter size reduction by a factor of 6. The implemented prototype shows decent audio performance with THD + N below 0.1 %....
Directory of Open Access Journals (Sweden)
Gabriele Grandi
2016-05-01
Full Text Available This paper gives the complete analysis of the output current ripple in three-phase voltage source inverters considering the different discontinuous pulse-width modulation (DPWM strategies. In particular, peak-to-peak current ripple amplitude is analytically evaluated over the fundamental period and compared among the most used DPWMs, including positive and negative clamped (DPWM+ and DPWM−, and the four possible combinations between them, usually named as DPWM0, DPWM1, DPWM2, and DPWM3. The maximum and the average values of peak-to-peak current ripple are estimated, and a simple method to correlate the ripple envelope with the ripple rms is proposed and verified. Furthermore, all the results obtained by DPWMs are compared to the centered pulse-width modulation (CPWM, equivalent to the space vector modulation to identify the optimal pulse-width modulation (PWM strategy as a function of the modulation index, taking into account the different average switching frequency. In this way, the PWM technique providing for the minimum output current ripple is identified over the whole modulation range. The analytical developments and the main results are experimentally verified by current ripple measurements with a three-phase PWM inverter prototype supplying an induction motor load.
Research and design of a novel current mode charge pump
Xianrui, Li; Xinquan, Lai; Yushan, Li; Qiang, Ye
2009-10-01
To meet the demands for a number of LEDs, a novel charge pump circuit with current mode control is proposed. Regulation is achieved by operating the current mirrors and the output current of the operational transconductance amplifier. In the steady state, the input current from power voltage retains constant, so reducing the noise induced on the input voltage source and improving the output voltage ripple. The charge pump small-signal model is used to describe the device's dynamic behavior and stability. Analytical predictions were verified by Hspice simulation and testing. Load driving is up to 800 mA with a power voltage of 3.6 V, and the output voltage ripple is less than 45 mV. The output response time is less than 8 μs, and the load current jumps from 400 to 800 mA.
Research and design of a novel current mode charge pump
Energy Technology Data Exchange (ETDEWEB)
Li Xianrui; Lai Xinquan; Li Yushan; Ye Qiang, E-mail: lixianrui4213@126.co [Research Institute of Design Circuit, Xidian University, Xi' an 710071 (China)
2009-10-15
To meet the demands for a number of LEDs, a novel charge pump circuit with current mode control is proposed. Regulation is achieved by operating the current mirrors and the output current of the operational transconductance amplifier. In the steady state, the input current from power voltage retains constant, so reducing the noise induced on the input voltage source and improving the output voltage ripple. The charge pump small-signal model is used to describe the device's dynamic behavior and stability. Analytical predictions were verified by Hspice simulation and testing. Load driving is up to 800 mA with a power voltage of 3.6 V, and the output voltage ripple is less than 45 mV. The output response time is less than 8 {mu}s, and the load current jumps from 400 to 800 mA.
Research and design of a novel current mode charge pump
Institute of Scientific and Technical Information of China (English)
Li Xianrui; Lai Xinquan; Li Yushan; Ye Qiang
2009-01-01
To meet the demands for a number of LEDs, a novel charge pump circuit with current mode control is proposed. Regulation is achieved by operating the current mirrors and the output current of the operational transcon ductance amplifier. In the steady state, the input current from power voltage retains constant, so reducing the noise induced on the input voltage source and improving the output voltage ripple. The charge pump small-signal model is used to describe the device's dynamic behavior and stability. Analytical predictions were verified by Hspice sim ulation and testing. Load driving is up to 800 mA with a power voltage of 3.6 V, and the output voltage ripple is less than 45 mV. The output response time is less than 8 μs, and the load current jumps from 400 to 800 mA.
Directory of Open Access Journals (Sweden)
S. D. Parkinson
2014-09-01
Full Text Available High-resolution direct numerical simulations (DNSs are an important tool for the detailed analysis of turbidity current dynamics. Models that resolve the vertical structure and turbulence of the flow are typically based upon the Navier–Stokes equations. Two-dimensional simulations are known to produce unrealistic cohesive vortices that are not representative of the real three-dimensional physics. The effect of this phenomena is particularly apparent in the later stages of flow propagation. The ideal solution to this problem is to run the simulation in three dimensions but this is computationally expensive. This paper presents a novel finite-element (FE DNS turbidity current model that has been built within Fluidity, an open source, general purpose, computational fluid dynamics code. The model is validated through re-creation of a lock release density current at a Grashof number of 5 × 106 in two and three dimensions. Validation of the model considers the flow energy budget, sedimentation rate, head speed, wall normal velocity profiles and the final deposit. Conservation of energy in particular is found to be a good metric for measuring model performance in capturing the range of dynamics on a range of meshes. FE models scale well over many thousands of processors and do not impose restrictions on domain shape, but they are computationally expensive. The use of adaptive mesh optimisation is shown to reduce the required element count by approximately two orders of magnitude in comparison with fixed, uniform mesh simulations. This leads to a substantial reduction in computational cost. The computational savings and flexibility afforded by adaptivity along with the flexibility of FE methods make this model well suited to simulating turbidity currents in complex domains.
Parkinson, S. D.; Hill, J.; Piggott, M. D.; Allison, P. A.
2014-09-01
High-resolution direct numerical simulations (DNSs) are an important tool for the detailed analysis of turbidity current dynamics. Models that resolve the vertical structure and turbulence of the flow are typically based upon the Navier-Stokes equations. Two-dimensional simulations are known to produce unrealistic cohesive vortices that are not representative of the real three-dimensional physics. The effect of this phenomena is particularly apparent in the later stages of flow propagation. The ideal solution to this problem is to run the simulation in three dimensions but this is computationally expensive. This paper presents a novel finite-element (FE) DNS turbidity current model that has been built within Fluidity, an open source, general purpose, computational fluid dynamics code. The model is validated through re-creation of a lock release density current at a Grashof number of 5 × 106 in two and three dimensions. Validation of the model considers the flow energy budget, sedimentation rate, head speed, wall normal velocity profiles and the final deposit. Conservation of energy in particular is found to be a good metric for measuring model performance in capturing the range of dynamics on a range of meshes. FE models scale well over many thousands of processors and do not impose restrictions on domain shape, but they are computationally expensive. The use of adaptive mesh optimisation is shown to reduce the required element count by approximately two orders of magnitude in comparison with fixed, uniform mesh simulations. This leads to a substantial reduction in computational cost. The computational savings and flexibility afforded by adaptivity along with the flexibility of FE methods make this model well suited to simulating turbidity currents in complex domains.
A New CMOS Current-Mode Folding Amplifier
Directory of Open Access Journals (Sweden)
M.A Al-Absi
2013-09-01
Full Text Available In this paper, a new CMOS current-mode folding amplifier is proposed. The circuit is designed using MOSFETs operating in strong inversion. The design produces a nearly ideal saw-tooth input-output characteristic which is a mandatory requirement in folding analog-to-digital converters. The functionality of the proposed circuit was confirmed using Tanner simulation tools in 0.35 µm CMOS technology. Simulation results are in excellent agreement with the theory.
New Universal Current-Mode Filter Using Non-Inverting Second-Generation Current-Conveyors
Muhammad Taher Abuelma'atti; Aamir Alam Farooqui
1995-01-01
A new universal active current-mode filter with single input and five outputs is presented. The proposed filter avoids the use of feedback in any part of the circuit and uses only one type of second-generation current-conveyors, grounded resistors, and grounded capacitors. The proposed circuit can simultaneously realize lowpass, highpass, bandpass, allpass, and notch biquadratic filter functions.
Laudanski, J.; Sumner, C.; Coombes, S.
2010-07-01
Thalamocortical (TC) neurones are known to express the low-voltage activated, inactivating Ca2+ current IT . The triggering of this current underlies the generation of low threshold Ca2+ potentials that may evoke single or bursts of action potentials. Moreover, this current can contribute to an intrinsic slow (dynamics for the gating variables in the model of IT . This model can be analyzed in closed form and is shown to support an unstable set of periodic orbits. Trajectories are repelled from these organizing centers until they reach the threshold for firing. By determining the condition for a grazing bifurcation (at the border between a spiking and nonspiking event) we show how knowledge of the unstable periodic orbits (existence and stability) can be combined with the grazing condition to determine an effective one-dimensional map that captures the essentials of the chaotic behavior. This map is discontinuous and has strong similarities with the universal limit mapping in grazing bifurcations derived in the context of impacting mechanical systems [A. B. Nordmark, Phys. Rev. E 55, 266 (1997)10.1103/PhysRevE.55.266].
Optimal Geometry of CMOS Voltage-Mode and Current-Mode Vertical Magnetic Hall Sensors
2015-01-01
Four different geometries of a vertical Hall sensor\\ud are presented and studied in this paper. The current spinning\\ud technique compensates for the offset and the sensors, driven in\\ud current-mode, provide a differential signal current for a possible\\ud capacitive integration over a defined time-slot. The sensors have\\ud been fabricated using a 6-metal 0.18-μm CMOS technology and\\ud fully experimentally tested. The optimal solution will be further\\ud investigated for bendable electronics. ...
Dynamics and stabilization of peak current-mode controlled buck converter with constant current load
Institute of Scientific and Technical Information of China (English)
冷敏瑞; 周国华; 张凯暾; 李振华
2015-01-01
The discrete iterative map model of peak current-mode controlled buck converter with constant current load (CCL), containing the output voltage feedback and ramp compensation, is established in this paper. Based on this model the com-plex dynamics of this converter is investigated by analyzing bifurcation diagrams and the Lyapunov exponent spectrum. The effects of ramp compensation and output voltage feedback on the stability of the converter are investigated. Experimental results verify the simulation and theoretical analysis. The stability boundary and chaos boundary are obtained under the theoretical conditions of period-doubling bifurcation and border collision. It is found that there are four operation regions in the peak current-mode controlled buck converter with CCL due to period-doubling bifurcation and border-collision bifur-cation. Research results indicate that ramp compensation can extend the stable operation range and transfer the operating mode, and output voltage feedback can eventually eliminate the coexisting fast-slow scale instability.
Dynamic Feedback Controlling Chaos in Current-Mode Boost Converter
Institute of Scientific and Technical Information of China (English)
LU Wei-Guo; ZHOU Luo-Wei; LUO Quan-Ming
2007-01-01
A method for the control of chaos in the current-mode boost converter is presented by using the first-order dynamic feedback control. The feedback part consists of a resistance and a capacitance in series. The system to be controlled is treated as a third-order model, and then the discrete mapping model is obtained by using the data-sampling method. By analysing the position of the maximum norm eigenvalue, the stable range of feedback gain is ascertained out and its optimization is also carried out. Finally, the results of simulation and experiment confirm the correctness of the theoretical analysis and the validity of the proposed means.
Inductor Current Sampled Feedback Control of Chaos in Current-Mode Boost Converter
Institute of Scientific and Technical Information of China (English)
Bo-Cheng Bao; Jian-Ping Xu; Yan Liang
2008-01-01
A chaos control strategy for chaotic current-mode boost converter is presented by using inductor current sampled feedback control technique. The quantitative analysis of control mechanism is performed by establishing a discrete alterative map of the controlled system. The stability criterion, feedback gain, and corresponding critical duty ratio are obtained from the eigenvalue of the map. The simulation results verify the theoretical analysis results of the control strategy.
Low-Voltage MOS Current Mode Logic Multiplexer
Directory of Open Access Journals (Sweden)
K. Gupta
2013-04-01
Full Text Available In this paper, a new low-voltage MOS current mode logic (MCML multiplexer based on the triple-tail cell concept is proposed. An analytical model for static parameters is formulated and is applied to develop a design approach for the proposed low-voltage MCML multiplexer. The delay of the proposed low-voltage MCML multiplexer is expressed in terms of the bias current and the voltage swing so that it can be traded off with the power consumption. The proposed low-voltage MCML multiplexer is analyzed for the three design cases namely high-speed, power-efficient, and low-power. Finally, a comparison in performance of the proposed low-voltage MCML multiplexer with the traditional MCML multiplexer is carried out for all the cases.
Log-Domain Current-mode Quadrature Sinusoidal Oscillator
Directory of Open Access Journals (Sweden)
P. Prommee
2011-09-01
Full Text Available A log-domain current-mode quadrature sinusoidal oscillator based on lossless integrators is presented. The circuit is a direct realization of a first-order differential equation for obtaining the lossy and lossless integrators. Each of the log-domain lossless integrators is realized by using only NPN transistors and a grounded capacitor for achieving low-power and fast response. The proposed oscillator uses two-lossless integrator loop which can be electronically tuned through bias currents. A validated BJT model which is used in SPICE simulation operated from a single power supply as low as 2.5V. The oscillation frequency is controlled over four decades of frequency. The total harmonic distortions for two-phases QSO (12MHz is obtained around 0.93% which enables fully integrated in telecommunication systems. The proposed circuit is also suitable for high-frequency applications. Nonideality studies are included and PSpice simulation results confirm the theoretical results.
Design of current mirror integration ROIC for snapshot mode operation
Shanker Gupta, Hari; Kiran Kumar, A. S.; Shojaei Baghini, M.; Chakrabarti, Subhananda; Mehta, Sanjeev; Chowdhury, Arup Roy; Sharma, Dinesh K.
2016-10-01
Current mirror integration (CMI) read out integrated circuit (ROIC) topology provides a low input impedance to photo-detectors and provides large injection efficiency, large charge handling capacity and snapshot mode operation without in-pixel opamps. The ROIC described in this paper has been implemented with a modified current mirror circuit, with matched PMOS pairs for detector input stage and its biasing. The readout circuit has been designed for 30 × 30 μm2 pixel size, 4 × 4 array size, variable frame rate, 5 Mega pixel per second (Mpps). Experimental performance of the test chip has achieved 15 Me charge handling capacity, a high dynamic range of 83 dB, 99.8% linearity and 99.96% injection efficiency. The ROIC design has been fabricated in 3.3 V 1P6M UMC 180 nm CMOS process and tested up to 5 MHz pixel rate at room and at cryogenic temperature.
Subnanosecond current mode detectors for prompt physical process diagnosis
Institute of Scientific and Technical Information of China (English)
无
1999-01-01
For prompt physical diagnosis, several types of subnanosecond current mode detectors have been developed,including scintillator detectors with large linear output current,GaAs:Cr and InP:Fe photoconductor detectors(PCD), and X-ray diodes(XRD), etc. The characteristic of scintillation light of BaF2 crystal doped with La and of plastic scintillator ST1422 with slow component quencher are described. As for the photoconductor detectors, the main performance of neutron damaged GaAs:Cr and InP:Fe were studied. In addition, the spectral response of an XRD with coaxial leading-out end was also studied. These detectors have been successfully applied to nuclear test diagnosis and ICF research.
Olivier, Michel; Gagnon, Marc-Daniel; Piché, Michel
2015-03-09
A strategy to align a mode-locked fiber laser with nonlinear polarization rotation is presented. This strategy is based on measurements of the output polarization state. It is shown that, as the angle of a motorized polarization controller inside the cavity is swept, the laser eventually reaches a mode-locked regime and the values of the Stokes parameters undergo an abrupt change. The sensing of this sudden variation is thus used to detect the mode-locking condition and a feedback mechanism drives the alignment of the polarization controller to force mode locking.
Self-Biasing High Precision CMOS Current Subtractor for Current-Mode Circuits
Directory of Open Access Journals (Sweden)
ARSLAN, E.
2013-11-01
Full Text Available In this study, a novel, differential pair based, high performance and high bandwidth current subtractor is proposed. Very low equivalent impedances are obtained at input ports n and p by using source follower transistors. Furthermore, the proposed circuit is self-biasing which makes it resistant to process, supply voltage and temperature variations. The proposed current subtractor can be used as an input stage for current-mode active circuits like current differencing buffered amplifier (CDBA, operational transresistance amplifier (OTRA and current differencing transconductance amplifier (CDTA which employ current subtractors. A numeric figure-of-merit is defined and it is used to demonstrate the superior performance of the proposed circuit.
Institute of Scientific and Technical Information of China (English)
Dong Jianfeng; Xu Shanjia
2006-01-01
The reflection and transmission characteristics of the guided modes in parallel-plate waveguides partially filled with one or multi chiral rods have been investigated by a method, which combines the multimode network theory with a rigorous mode matching procedure. The formulas of the reflection and transmission coefficient matrix are derived. The numerical results for different cases are presented and have indicated that the chirality parameters and the geometrical dimensions of the chiral rods have significant influence on the reflection and transmission characteristics of the guided modes.
Multiplicity counting from fission chamber signals in the current mode
Pázsit, I.; Pál, L.; Nagy, L.
2016-12-01
In nuclear safeguards, estimation of sample parameters using neutron-based non-destructive assay methods is traditionally based on multiplicity counting with thermal neutron detectors in the pulse mode. These methods in general require multi-channel analysers and various dead time correction methods. This paper proposes and elaborates on an alternative method, which is based on fast neutron measurements with fission chambers in the current mode. A theory of "multiplicity counting" with fission chambers is developed by incorporating Böhnel's concept of superfission [1] into a master equation formalism, developed recently by the present authors for the statistical theory of fission chamber signals [2,3]. Explicit expressions are derived for the first three central auto- and cross moments (cumulants) of the signals of up to three detectors. These constitute the generalisation of the traditional Campbell relationships for the case when the incoming events represent a compound Poisson distribution. Because now the expressions contain the factorial moments of the compound source, they contain the same information as the singles, doubles and triples rates of traditional multiplicity counting. The results show that in addition to the detector efficiency, the detector pulse shape also enters the formulas; hence, the method requires a more involved calibration than the traditional method of multiplicity counting. However, the method has some advantages by not needing dead time corrections, as well as having a simpler and more efficient data processing procedure, in particular for cross-correlations between different detectors, than the traditional multiplicity counting methods.
Dynamics and stabilization of peak current-mode controlled buck converter with constant current load
Leng, Min-Rui; Zhou, Guo-Hua; Zhang, Kai-Tun; Li, Zhen-Hua
2015-10-01
The discrete iterative map model of peak current-mode controlled buck converter with constant current load (CCL), containing the output voltage feedback and ramp compensation, is established in this paper. Based on this model the complex dynamics of this converter is investigated by analyzing bifurcation diagrams and the Lyapunov exponent spectrum. The effects of ramp compensation and output voltage feedback on the stability of the converter are investigated. Experimental results verify the simulation and theoretical analysis. The stability boundary and chaos boundary are obtained under the theoretical conditions of period-doubling bifurcation and border collision. It is found that there are four operation regions in the peak current-mode controlled buck converter with CCL due to period-doubling bifurcation and border-collision bifurcation. Research results indicate that ramp compensation can extend the stable operation range and transfer the operating mode, and output voltage feedback can eventually eliminate the coexisting fast-slow scale instability. Project supported by the National Natural Science Foundation of China (Grant No. 61371033), the Fok Ying-Tung Education Foundation for Young Teachers in the Higher Education Institutions of China (Grant No. 142027), the Sichuan Provincial Youth Science and Technology Fund, China (Grant Nos. 2014JQ0015 and 2013JQ0033), and the Fundamental Research Funds for the Central Universities, China (Grant No. SWJTU11CX029).
ICRF fast wave current drive and mode conversion current drive in EAST tokamak
Yin, L.; Yang, C.; Gong, X. Y.; Lu, X. Q.; Du, D.; Chen, Y.
2017-10-01
Fast wave in the ion-cyclotron resonance frequency (ICRF) range is a promising candidate for non-inductive current drive (CD), which is essential for long pulse and high performance operation of tokamaks. A numerical study on the ICRF fast wave current drive (FWCD) and mode-conversion current drive (MCCD) in the Experimental Advanced Superconducting Tokamak (EAST) is carried out by means of the coupled full wave and Ehst-Karney parameterization methods. The results show that FWCD efficiency is notable in two frequency regimes, i.e., f ≥ 85 MHz and f = 50-65 MHz, where ion cyclotron absorption is effectively avoided, and the maximum on-axis driven current per unit power can reach 120 kA/MW. The sensitivity of the CD efficiency to the minority ion concentration is confirmed, owing to fast wave mode conversion, and the peak MCCD efficiency is reached for 22% minority-ion concentration. The effects of the wave-launch position and the toroidal wavenumber on the efficiency of current drive are also investigated.
Why 4-H Members Leave: A Study of Discontinuance through Both Current 4-H Members and Former Members
Chilek, Kevin Dwayne
2012-01-01
4-H members quit. It is part of every 4-H program, and according to the research, it is even part of growing up. If only we knew why they quit, we could possibly do something about it. To date, the reasons youth join 4-H have been more thoroughly researched than the reasons they quit. This study explores why youth choose to discontinue membership…
Why 4-H Members Leave: A Study of Discontinuance through Both Current 4-H Members and Former Members
Chilek, Kevin Dwayne
2012-01-01
4-H members quit. It is part of every 4-H program, and according to the research, it is even part of growing up. If only we knew why they quit, we could possibly do something about it. To date, the reasons youth join 4-H have been more thoroughly researched than the reasons they quit. This study explores why youth choose to discontinue membership…
A New Current Mode SIMO-Type Universal Biquad Employing Multi-Output Current Conveyors (MOCCIIs
Directory of Open Access Journals (Sweden)
S. Du
2009-04-01
Full Text Available This study presents a new current-mode singleinput and multi-output (SIMO type universal biquad circuit using second generation multi-output current conveyors (MOCCII as the active components. The proposed circuit employs three MOCCIIs, two grounded capacitors and four grounded resistors, therefore offers electroning tuning possibilities. It can simultaneously realize second order low-pass, band-pass, high-pass, notch and all-pass filters. The circuit is cascadable and has low sensitivities. It provides independent control of ω0 (natural angular frequency and Q (quality factor. The influences of MOCCII parasitic elements have been analyzed and simulated using PSPICE. Experimental results including frequency responses of low-pass, high-pass, band-pass and band-stop filters, as well as frequency responses of filters with different ω0 (keeping Q invariable and different Q (keeping ω0 invariable are shown to be in agreement with theory.
Current-diffusive ballooning mode in low shear and negative shear regions of tokamaks
Energy Technology Data Exchange (ETDEWEB)
Yagi, Masatoshi; Azumi, Masafumi (Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment); Itoh, Kimitaka; Itoh, Sanae; Fukuyama, Atsushi
1994-01-01
The stability of the current-diffusive ballooning mode in tokamaks with high toroidal mode number is analyzed in the region of second stability against the ideal magnetohydrodynamic mode. It is found that the growth rate of the current-diffusive ballooning mode is decreased upon the reduction of the geodesic curvature driving force. The reduction of thermal conductivity in the limit of very weak shear or negative shear in comparison with standard shear is also shown. (author).
Yamaguchi, T; Nakamura, K; Yamaguchi, S; Hasegawa, Y
2002-01-01
Experiments of Peltier current lead (PCL) were performed by the way of half-wave-rectified current (HWRC) for an evaluation of the PCL system in the drive with the large-rippled current. The current ripple of the HWRC is large, and we discussed the cooling capability of the current ripple. The experimental results revealed that the temperature difference of the thermoelectric-element (TE) increased with the magnitude of the current in the PCL system, despite the large current ripple. Calorimetric measurements revealed that the PCL reduced the heat leak of 60% for the peak current 90A. We compared the PCL systems of the direct current (dc) mode and the HWRC mode. The results showed that the current dependence of the temperature difference in the HWRC mode did not match that of the dc mode, but those of the heat leak matched well. The performance of the Peltier cooling in the HWRC mode is reduced to be 2/pi time of the Seebeck coefficient for the dc mode by using the time-average method. (author)
Energy Technology Data Exchange (ETDEWEB)
Yamaguchi, Takayuki; Ohtaki, Naohiro; Nakamura, Keiji; Yamaguchi, Satarou [Chubu Univ., Kasugai, Aichi (Japan); Hasegawa, Yasuhiro [Saitama Univ., Saitama (Japan)
2002-09-01
Experiments of Peltier current lead (PCL) were performed by the way of half-wave-rectified current (HWRC) for an evaluation of the PCL system in the drive with the large-rippled current. The current ripple of the HWRC is large, and we discussed the cooling capability of the current ripple. The experimental results revealed that the temperature difference of the thermoelectric-element (TE) increased with the magnitude of the current in the PCL system, despite the large current ripple. Calorimetric measurements revealed that the PCL reduced the heat leak of 60% for the peak current 90A. We compared the PCL systems of the direct current (dc) mode and the HWRC mode. The results showed that the current dependence of the temperature difference in the HWRC mode did not match that of the dc mode, but those of the heat leak matched well. The performance of the Peltier cooling in the HWRC mode is reduced to be 2/{pi} time of the Seebeck coefficient for the dc mode by using the time-average method. (author)
New Gain Controllable Resistor-less Current-mode First Order Allpass Filter and its Application
Directory of Open Access Journals (Sweden)
W. Jaikla
2012-04-01
Full Text Available New first order allpass filter (APF in current mode, constructed from 2 CCCCTAs and grounded capacitor, is presented. The current gain and phase shift can be electronically /orthogonally controlled. Low input and high output impedances are achieved which make the circuit to be easily cascaded to the current-mode circuit without additional current buffers. The operation of the proposed filter has been verified through simulation results which confirm the theoretical analysis. The application example as current-mode quadrature oscillator with non-interactive current control for both of oscillation condition and oscillation frequency is included to show the usability of the proposed filter.
Anisotropic thermoelement in emf and current generation mode
Directory of Open Access Journals (Sweden)
Anatychuk L. I.
2011-06-01
Full Text Available Computer methods for the description of the anisotropic thermoelement (AT properties with regard to all necessary model approximations have been elaborated. Configurations of eddy thermoelectric currents in the anisotropic thermoele-ment caused by current contacts have been found. The pro-perties of the AT with regard to temperature dependences of material properties, contact resistances and current contacts have been determined for concrete cases. Optimal dimensions of current contacts have been found. The optimization of AT construction allowed to increase its efficiency by 15%.
Chattering Suppression for DSP Based Sliding Mode Current Control of PM DC Drives
DEFF Research Database (Denmark)
Dal, Mehmet; Teodorescu, Remus
2009-01-01
This paper investigates several chattering suppression methods for DSP based implementation of sliding mode control (SMC). It concentrates on the ‘equivalent-control-dependent' and ‘state-dependent' gain adjustment methods proposed in recent theoretical studies, and tests the effectiveness...... performed separately, and so various combinations of these methods are tested to find the best solution for chattering elimination. Discontinuous control signal averaging, which is a common chattering reduction technique, is made possible while the system is online by the use of a tunable low-pass filter...
Zeng, Hang-li
2010-01-01
This paper has made an investigation on the current writing teaching mode among English majors in normal universities in China, by means of questionnaire, interview and class observation. The study finds out that the current writing teaching mode is not purely product approach or process approach. In fact, the two approaches to writing co-exist in…
SRG POSITION SENSORLESS TECHNIQUE WITH CURRENT CHOPPING MODE
Institute of Scientific and Technical Information of China (English)
ZhuXuezhong; LiuDiji; GuiXiaojie; LiuChuang
2002-01-01
A onvel current chopping strategy for switched reluc-tance generator(SRG)-a full conducted current chopping(FCCC)scheme is presented,According to characteristics lf phase current wave of SRG generating operation,it can be generated under sensorless condition without an addi-tional circuit or a position signal algorithm.Simulational results show the feasibility of this scheme.Experimental results of a 6kW6/4configuration SRG show its simplic-ity and high reliability with little decrease in efficiency.Soit will be widely used.
Xenon excimer emission from multicapillary discharges in direct current mode
Lee, Byung-Joon; Rahaman, Hasibur; Nam, Sang Hoon; Giapis, Konstantinos P.; Iberler, Marcus; Jacoby, Joachim; Frank, Klaus
2011-08-01
Microdischarges in xenon have been generated in a pressure range of 400-1013 mbar with a fixed flow rate of 100 sccm. These microdischarges are obtained from three metallic capillary tubes in series for excimer emission. Total discharge voltage is thrice as large as that of a single capillary discharge tube at current levels of up to 12 mA. Total spectral irradiance of vacuum ultraviolet (VUV) emission also increases significantly compared to that of the single capillary discharge. Further, the irradiance of the VUV emission is strongly dependent on pressure as well as the discharge current.
Xenon excimer emission from multicapillary discharges in direct current mode
Energy Technology Data Exchange (ETDEWEB)
Lee, Byung-Joon; Rahaman, Hasibur; Nam, Sang Hoon [Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784 (Korea, Republic of); Giapis, Konstantinos P. [Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125 (United States); Iberler, Marcus; Jacoby, Joachim [Institute of Applied Physics, Goethe University, Max-von-Laue-St. 1, 60438 Frankfurt am Main (Germany); Frank, Klaus [Physics Department I, F.A., University of Erlangen-Nuremberg, D-91058 Erlangen (Germany)
2011-08-15
Microdischarges in xenon have been generated in a pressure range of 400-1013 mbar with a fixed flow rate of 100 sccm. These microdischarges are obtained from three metallic capillary tubes in series for excimer emission. Total discharge voltage is thrice as large as that of a single capillary discharge tube at current levels of up to 12 mA. Total spectral irradiance of vacuum ultraviolet (VUV) emission also increases significantly compared to that of the single capillary discharge. Further, the irradiance of the VUV emission is strongly dependent on pressure as well as the discharge current.
INVESTIGATION OF MICROPROCESSOR TRANSFORMER CURRENT PROTECTION IN SHORT CIRCUIT FAULT MODES
Directory of Open Access Journals (Sweden)
M. S. Loman
2014-01-01
Full Text Available The paper presents an investigation on transformer current protection with blocking against magnetizing inrush current in short circuit fault modes. It has been shown that the proposed magnetizing in-rush current blocking algorithm can be implemented in microprocessor current protections of transformers.
A current-mode buck DC-DC controller with adaptive on-time control
Energy Technology Data Exchange (ETDEWEB)
Li Yanming; Lai Xinquan; Ye Qiang; Yuan Bing; Chen Fuji [Institute of Electronic CAD, Xidian University, Xi' an 710071 (China); Jia Xinzhang, E-mail: ymli2004@126.co, E-mail: xqlai@mail.xidian.edu.c [Microelectronics Institute, Xidian University, Xi' an 710071 (China)
2009-02-15
A current-mode buck DC-DC controller based on adaptive on-time (AOT) control is presented. The on-time is obtained by the techniques of input feedforward and output feedback, and the adaptive control is achieved by a sample-hold and time-ahead circuit. The AOT current-mode control scheme not only obtains excellent transient response speed, but also achieves the independence of loop stability on output capacitor ESR. In addition, the AOT current-mode control does not have subharmonic oscillation phenomenon seen in fixed frequency peak current-mode control, so there is no need of the slope compensation circuit. The auto-skip pulse frequency modulation (PFM) mode improves the conversion efficiency of light load effectively. The controller has been fabricated with UMC 0.6-mum BCD process successfully and the detailed experimental results are shown.
Xenon excimer emission from multicapillary discharges in direct current mode
Lee, Byung-Joon; Rahaman, Hasibur; Nam, Sang Hoon; Giapis, Konstantinos P.; Iberler, Marcus; Jacoby, Joachim; Frank, Klaus
2012-01-01
Microdischarges in xenon have been generated in a pressure range of 400–1013 mbar with a fixed flow rate of 100 sccm. These microdischarges are obtained from three metallic capillary tubes in series for excimer emission. Total discharge voltage is thrice as large as that of a single capillary discharge tube at current levels of up to 12 mA. Total spectral irradiance of vacuum ultraviolet (VUV) emission also increases significantly compared to that of the single capillary discharge. Further, t...
Electrical Discharge Machining Flyback Converter using UC3842 Current Mode PWM Controller
Directory of Open Access Journals (Sweden)
Nazriah Mahmud
2014-10-01
Full Text Available This paper presents a current mode Pulse Width Modulation (PWM controlled Flyback converter using UC3842 for Electrical Discharge Machining current generator control circuit. Circuit simplicity and high efficiency can be achieved by a Flyback converter with current mode PWM controller. The behaviors of the system's operation is analyzed and discussed by varying the load resistance. Matlab sofware is used to simulate the Flyback converter where a prototype has been built and tested to verify it's performance.
3D reconnection due to oblique modes: a simulation of Harris current sheets
Directory of Open Access Journals (Sweden)
G. Lapenta
2000-01-01
Full Text Available Simulations in three dimensions of a Harris current sheet with mass ratio, mi/me = 180, and current sheet thickness, pi/L = 0.5, suggest the existence of a linearly unstable oblique mode, which is independent from either the drift-kink or the tearing instability. The new oblique mode causes reconnection independently from the tearing mode. During the initial linear stage, the system is unstable to the tearing mode and the drift kink mode, with growth rates that are accurately described by existing linear theories. How-ever, oblique modes are also linearly unstable, but with smaller growth rates than either the tearing or the drift-kink mode. The non-linear stage is first reached by the drift-kink mode, which alters the initial equilibrium and leads to a change in the growth rates of the tearing and oblique modes. In the non-linear stage, the resulting changes in magnetic topology are incompatible with a pure tearing mode. The oblique mode is shown to introduce a helical structure into the magnetic field lines.
Investigation of lower hybrid current drive during H-mode in EAST tokamak
Institute of Scientific and Technical Information of China (English)
Li Miao-Hui; Liu Fu-Kun; Wang Mao; Xu Han-Dong; Wan Bao-Nian; Ding Bo-Jiang; Kong Er-Hua; Zhang Lei; Zhang Xin-Jun; Qian Jin-Ping; Yan Ning; Han Xiao-Feng; Shan Jia-Fang
2011-01-01
H-mode discharges with lower hybrid current drive (LHCD) alone are achieved in EAST divertor plasma over a wide parameter range.These H-mode discharges are characterized by a sudden drop in Dα emission and a spontaneous rise in main plasma density.Good lower hybrid (LH) coupling during H-mode is obtained by putting the plasma close to the antenna and by injecting D2 gas from a pipe near the grill mouse.The analysis of lower hybrid current drive properties shows that the LH deposition profile shifts off axis during H-mode,and current drive (CD) efficiency decreases due to the increase in density.Modeling results of H-mode discharges with a general ray tracing code GENRAY are reported.
On the merits of heating and current drive for tearing mode stabilization
De Lazzari, D.; Westerhof, E.
2009-01-01
Neoclassical tearing modes (NTMs) are magnetohydrodynamic modes that can limit the performance of high beta discharges in a tokamak, leading eventually to a plasma disruption. A NTM is sustained by the perturbation of the 'bootstrap' current, which is a consequence of the pressure flatteni
Design and Implementation of Digital Current Mode Controller for DC-DC Converters
DEFF Research Database (Denmark)
Taeed, Fazel
to be regulated by a closed-loop controller. The Peak Current Mode Control (PCMC) is one of the most promising control methods for dc-dc converters. It has been known for high bandwidth (speed), and inherent current protection. Increasing the controller bandwidth decreases the output filter size and cost. Analog...... a bandwidth of 1/10 of the switching frequency. In the current state-of-the-art, the best reported digital PCMC has crossover frequency of 1/15 of the switching frequency. In this PhD study a novel digital PCMC with negligible delay in the inner current loop has been proposed. The proposed solution has...... are eliminated in current mode control; applying the current mode control in high efficiency dc-dc converters results in much higher controller bandwidth....
Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode
Poehlmann, Flavio R.; Cappelli, Mark A.; Rieker, Gregory B.
2010-01-01
Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma def...
Phase Current Differential Protection for Transformers in Wye-delta Mode
Directory of Open Access Journals (Sweden)
Zhe Zhang
2012-10-01
Full Text Available For the current transformers (CTs on the delta side measure the line current instead of the phase current, line current differential protection is adopted in transformers connected in wye-delta mode currently. However, the symmetry feature of inrush current in line current differential protection may invalidate the inrush current restrained criterion. A calculating method of current through delta windings according the measured current from CT is proposed in this paper. Using this calculated current, phase current differential protection can be realized. Based on the method an adaptive second harmonic restrained scheme for magnetizing inrush current is presented. The scheme not only adaptively adjusts the secondary harmonic ratio of restrained current but also guarantees the fast action when transformers with internal faults are no-load energized. Consequently the performance of transformer differential protection is greatly improved. Simulation results in Matlab/Simulink validate the proposed method.
Zhang, Shengyao; Ming Leung, Chung; Kuang, Wei; Wing Or, Siu; Ho, S. L.
2013-05-01
A heterostructure possessing two concurrent operational modes: current sensing (CS) mode and current transduction (CT) mode and an enhanced current sensitivity associated with the CT mode is proposed by combining a magnetoelectric ring (MER) with a piezoelectric transformer (PET). The MER is a ring-shaped magnetoelectric laminate having an axially polarized Pb(Zr, Ti)O3 (PZT) piezoelectric ceramic ring sandwiched between two circumferentially magnetized, inter-magnetically biased Tb0.3Dy0.7Fe1.92 (Terfenol-D) short-fiber/NdFeB magnet/epoxy three-phase magnetostrictive composite rings, while the PET is a Rosen-type PZT piezoelectric ceramic transformer. The current sensitivity (SI) and magnetoelectric voltage coefficient (αV) of the heterostructure in the two operational modes are evaluated theoretically and experimentally. The CS mode provides a large SI of ˜10 mV/A over a flat frequency range of 10 Hz-40 kHz with a high resonance SI of 157 mV/A at 62 kHz. The CT mode gives a 6.4-times enhancement in resonance SI, reaching 1000 mV/A at 62 kHz, as a result of the amplified vortex magnetoelectric effect caused by the vortex magnetoelectric effect in the MER, the matching of the resonance frequencies between the MER and the PET, and the resonance voltage step-up effect in the PET.
The investigation of reverse traction current influence on tone track circuit modes
Directory of Open Access Journals (Sweden)
E.I.Jasсhuk
2012-12-01
Full Text Available Introduction: With the introduction of high-speed traffic there is an increased consumption of traction current by new types of rolling stock. This issue is important, as high levels of traction currents can have not only prevents, but also a dangerous impact on the equipment of railway automation devices. It is necessary to investigate the propagation of traction currents and potentials along the rails. Objective: Investigate the propagation of traction currents and potentials along the rails, the determination of critical currents, which not executed tone track circuits modes. Methods: In order to investigate the mathematical model, and the method of calculation tone track circuits modes was used. Results: By means of mathematical model, which includes being several rolling-stocks at the feeder zone, different rail resistance and isolation, the diagrams of currents and potentials propagations for DC and AC electric traction have been obtained. A comparative analysis of the experimental data and the results of the investigation has been realized. Based on received levels of reverse traction current their influence on track circuit modes has been investigated. Conclusions: The reverse traction current level near the substation and rolling-stock can be more than 600A. Great reverse traction current levels have an influence on tonal track circuit functioning, namely normal and shunt modes. When the traction current arrives 200 A there is a reduction criteria of tonal track circuits.
Zhou, Guo-Hua; Xu, Jian-Ping; Bao, Bo-Cheng; Jin, Yan-Yan
2010-06-01
The discrete iterative map models of peak current-mode (PCM) and valley current-mode (VCM) controlled buck converters, boost converters, and buck-boost converters with ramp compensation are established and their dynamical behaviours are investigated by using the operation region, parameter space map, bifurcation diagram, and Lyapunov exponent spectrum. The research results indicate that ramp compensation extends the stable operation range of the PCM controlled switching dc-dc converter to D > 0.5 and that of the VCM controlled switching dc-dc converter to D converters with ramp compensation, VCM controlled switching dc-dc converters with ramp compensation exhibit interesting symmetrical dynamics. Experimental results are given to verify the analysis results in this paper.
Current Mode Full-Wave Rectifier Based on a Single MZC-CDTA
Directory of Open Access Journals (Sweden)
Neeta Pandey
2013-01-01
Full Text Available This paper presents a current mode full-wave rectifier based on single modified Z copy current difference transconductance amplifier (MZC-CDTA and two switches. The circuit is simple and is suitable for IC implementation. The functionality of the circuit is verified with SPICE simulation using 0.35 μm TSMC CMOS technology parameters.
Directory of Open Access Journals (Sweden)
Jiun-Wei Horng
2012-01-01
Full Text Available A configuration for realizing low input and high output impedances current-mode multifunction filters using multiple output second-generation current conveyors (MOCCIIs is presented. From the proposed circuit configuration, first-order allpass, highpass, lowpass and second-order allpass, notch, bandpass filters can be obtained. The simulation results confirm the theoretical analysis.
Reducing the beam current in Linac4 in pulse to pulse mode.
Lallement, JB; CERN. Geneva. BE Department
2009-01-01
In order to deliver different beam intensities to users, we studied the possibility of varying the Linac4 beam current at PS Booster injection in pulse to pulse mode. This report gives the possible configurations of Linac4 Low and Medium Energy Beam Transport lines (LEBT and MEBT) that lead to a consistent current reduction.
Directory of Open Access Journals (Sweden)
J. Horng
2009-12-01
Full Text Available A high-order current-mode and transimpedance-mode universal filter with multiple-inputs and two-outputs based on multiple output second-generation current conveyors (MOCCIIs is introduced. By choosing the input current terminals appropriately, the current-mode and transimpedance-mode lowpass, bandpass, highpass, notch or allpass filters can be obtained without component matching conditions. The proposed nth order universal filter requires (n+1 MOCCIIs, (n+1 resistors and n grounded capacitors. As examples, the first-order, biquadratic and third-order universal filters are given and compared with previous published works.
High-Performance Long NoC Link Using Delay-Insensitive Current-Mode Signaling
Directory of Open Access Journals (Sweden)
Ethiopia Nigussie
2007-01-01
Full Text Available High-performance long-range NoC link enables efficient implementation of network-on-chip topologies which inherently require high-performance long-distance point-to-point communication such as torus and fat-tree structures. In addition, the performance of other topologies, such as mesh, can be improved by using high-performance link between few selected remote nodes. We presented novel implementation of high-performance long-range NoC link based on multilevel current-mode signaling and delay-insensitive two-phase 1-of-4 encoding. Current-mode signaling reduces the communication latency of long wires significantly compared to voltage-mode signaling, making it possible to achieve high throughput without pipelining and/or using repeaters. The performance of the proposed multilevel current-mode interconnect is analyzed and compared with two reference voltage mode interconnects. These two reference interconnects are designed using two-phase 1-of-4 encoded voltage-mode signaling, one with pipeline stages and the other using optimal repeater insertion. The proposed multilevel current-mode interconnect achieves higher throughput and lower latency than the two reference interconnects. Its throughput at 8 mm wire length is 1.222 GWord/s which is 1.58 and 1.89 times higher than the pipelined and optimal repeater insertion interconnects, respectively. Furthermore, its power consumption is less than the optimal repeater insertion voltage-mode interconnect, at 10 mm wire length its power consumption is 0.75 mW while the reference repeater insertion interconnect is 1.066 mW. The effect of crosstalk is analyzed using four-bit parallel data transfer with the best-case and worst-case switching patterns and a transmission line model which has both capacitive coupling and inductive coupling.
A wide bandwidth free-electron laser with mode locking using current modulation.
Energy Technology Data Exchange (ETDEWEB)
Kur, E.; Dunning, D. J.; McNeil, B. W. J.; Wurtele, J.; Zholents, A. A. (Accelerator Systems Division (APS)); (Univ. of California at Berkeley); (Univ. of Strathclyde); (STFC Daresbury Lab.); (LBNL)
2011-01-20
A new scheme for mode locking a free-electron laser amplifier is proposed based on electron beam current modulation. It is found that certain properties of the original concept, based on the energy modulation of electrons, are improved including the spectral brightness of the source and the purity of the series of short pulses. Numerical comparisons are made between the new and old schemes and between a mode-locked free-electron laser and self-amplified spontaneous emission free-electron laser. Illustrative examples using a hypothetical mode-locked free-electron laser amplifier are provided. The ability to generate intense coherent radiation with a large bandwidth is demonstrated.
Analysis of current-bidirectional buck-boost based switch-mode audio amplifier
DEFF Research Database (Denmark)
Bolten Maizonave, Gert; Andersen, Michael A. E.; Kjærgaard, Claus
2011-01-01
The following studdy was carried out in order to assses quantitatively the performannce of the buck--boost converter whhen used as swiitch-mode audio amplifier. It comprises of, to beggin with, the de limitation of design criteria bassed on the state of-the-art solution, which is based...... in a differential mode buckbased amplifier with a boost converter as power supply. The averaged switch modelling of the differential mode current bidirectional topology is also used, in order to analyze the steady state and frequency-wise behaviour of this converter and parameterize it to meet the design criteria...... in such configuration when applied for audio....
Analisys of Current-Bidirectional Buck-Boost Based Automotive Switch-Mode Audio Amplifier
DEFF Research Database (Denmark)
Bolten Maizonave, Gert; Andersen, Michael A. E.; Kjærgaard, Claus
2011-01-01
The following study was carried out in order to assess quantitatively the performance of the buck-boost converter when used as switch-mode audio amplifier. It comprises of, to begin with, the delimitation of design criteria based on the state-ofthe- art solution, which is based in a differential...... mode buck-based amplifier with a boost converter as power supply. The averaged switch modelling of the differential mode current bidirectional topology is also used, in order to analyze the steady state and frequency domain behaviour of this converter and parameterize it to meet the design criteria...... in such configuration when applied for audio....
Generalized Design Method for Voltage-Controlled Current-Mode Multifunction Filters
Directory of Open Access Journals (Sweden)
I. Lattenberg
2009-11-01
Full Text Available In the article, the Generalized Current Follower Transconductance Amplifier (GCFTA element for generalized frequency filter design and a novel active element, the Programmable Current Amplifier (PCA for the realization of the current-mode analog blocks, are presented. The paper also presents a method of general frequency filter design, whereas the basic circuit is a general autonomous circuit using GCFTA, PCA elements and general admittances. The properties of the proposed filter have been verified using PSPICE simulations.
Current-mode subthreshold MOS circuits for analog VLSI neural systems
Andreou, Andreas G.; Boahen, Kwabena A.; Pouliquen, Philippe O.; Pavasovic, Aleksandra; Jenkins, Robert E.
1991-03-01
An overview of the current-mode approach for designing analog VLSI neural systems in subthreshold CMOS technology is presented. Emphasis is given to design techniques at the device level using the current-controlled current conveyor and the translinear principle. Circuits for associative memory and silicon retina systems are used as examples. The design methodology and how it relates to actual biological microcircuits are discussed.
Current-mode subthreshold MOS circuits for analog VLSI neural systems.
Andreou, A G; Boahen, K A; Pouliquen, P O; Pavasovic, A; Jenkins, R E; Strohbehn, K
1991-01-01
An overview of the current-mode approach for designing analog VLSI neural systems in subthreshold CMOS technology is presented. Emphasis is given to design techniques at the device level using the current-controlled current conveyor and the translinear principle. Circuits for associative memory and silicon retina systems are used as examples. The design methodology and how it relates to actual biological microcircuits are discussed.
Directory of Open Access Journals (Sweden)
W. Chunhua
2010-04-01
Full Text Available This paper proposes a new current conveyorbased high-output impedance single-input three-output current mode filter with minimum configuration. It contains two dual output second generation current conveyors, one third generation dual output current conveyor, and four grounded resistors and capacitors. The circuit simultaneously provides low-pass, band-pass, and high-pass filtering outputs, without any passive component matching conditions and restrictions on input signals. Additionally, the proposed circuit offers following advantages: Minimum active and passive element count, high output and low input impedances, suitable for cascading identical currentmode sections, all passive elements are grounded (no virtual grounding, low natural frequency and Q-factor sensitivities. The influences of non-ideal current conveyors on the proposed circuit are researched in the last.
Energy Technology Data Exchange (ETDEWEB)
Oliveira Junior, Azauri Albano de; Maciel, Carlos Dias; Cichy, Elineri Cassia C.; Gongora, Vicente de Lima [Universidade de Sao Paulo (EESC/USP), Sao Carlos, SP (Brazil). Escola de Engenharia], Emails: azaurijr@sel.eesc.usp.br, maciel@sel.eesc.usp.br, elineri@uol.com.br, vicente@ldapalm.com.br; Barbosa, Lucio dos Reis [Universidade Estadual de Londrina (UEL), PR (Brazil)], Email: lbarbosa@uel.br; Pereira, Adriano Alves [Universidade Federal de Uberlandia (UFU), MG (Brazil)], Email: aapereira@ufu.br
2006-07-01
This work focuses on control of power inverter technologies for connecting any possible Dc energy system to a single-phase using a Current Mode Voltage Mode Control-CMVMC. In this way a CMVMC can control only one power inverter in two operation modes. In current mode the control inject the active power in the utility and voltage control keeping loads always on with energy from the alternative DC sources. When installed near big centers the control will choose the correctly operation or current mode or voltage mode depend on if the utility is present or no. This advanced, robust control strategies can determine the maximum on-line limit current from the DC energy, without DC current component and also free of island operation. The feasibility of this new control was digitally simulated and implemented in analogic way. (author)
Wang, Chunhua; Lin, Hairong
2015-09-01
In this study, a new versatile active element, namely multifunction current differencing cascaded transconductance amplifier (MCDCTA), is proposed. This device which adopts a simple configuration enjoys the performances of low-voltage, low-input and high-output impedance, wide bandwidth etc. It simplifies the design of the current-mode analog signal processing circuit greatly, especially the design of high-order filter and oscillator circuits. Moreover, an example as a new current-mode multiphase sinusoidal oscillator (MSO) using MCDCTA is described in this paper. The proposed oscillator, which employs only one MCDCTA and minimum grounded passive elements, is easy to be realized. It can provide random n (n being odd or even) output current signals and these output currents are equally spaced in phase all at high output impedance terminals. Its oscillation condition and the oscillation frequency can be adjusted independently, linearly and electronically by controlling the bias currents of MCDCTA. The operation of the proposed oscillator has been testified through PSPICE simulation and experimental results.
On the drift-sausage mode in one-dimensional current sheet
Yoon, Peter H.; Lui, A. T. Y.
2001-02-01
This article presents a two-fluid stability analysis of Harris current sheet equilibrium under the assumption of charge quasi-neutrality. It is found that the charge neutrality condition leads to sausage-type fluctuations, which propagate along the direction of the cross-field current flow, hence the drift-sausage mode. It is also shown that solutions which correspond to kink-type perturbations do not exist under the present assumption of charge neutrality. In view of the fact that a substantial body of simulation works exist which report predominantly kink-like perturbations, and that analytical theories which do not assume charge quasi-neutrality predict that the kink-type mode is a dominant unstable mode, it is concluded that the assumption of quasi-neutrality may be a poor choice in describing the stability of Harris current sheet equilibrium.
HHFW Heating and Current Drive Studies of NSTX H-Mode Plasmas
Energy Technology Data Exchange (ETDEWEB)
G. Taylor, P.T. Bonoli, D.L. Green, R.W. Harvey, J.C. Hosea, E.F. Jaeger, B.P. LeBlanc, R. Maingi, C.K. Phillips, P.M. Ryan, E.J. Valeo, J.R. Wilson, J.C. Wright, and the NSTX Team
2011-06-08
30 MHz high-harmonic fast wave (HHFW) heating and current drive are being developed to assist fully non-inductive plasma current (I{sub p}) ramp-up in NSTX. The initial approach to achieving this goal has been to heat I{sub p} = 300 kA inductive plasmas with current drive antenna phasing in order to generate an HHFW H-mode with significant bootstrap and RF-driven current. Recent experiments, using only 1.4 MW of RF power (P{sub RF}), achieved a noninductive current fraction, f{sub NI} {approx} 0.65. Improved antenna conditioning resulted in the generation of I{sub p} = 650 kA HHFW H-mode plasmas, with f{sub NI} {approx} 0.35, when P{sub RF} {ge} 2.5 MW. These plasmas have little or no edge localized mode (ELM) activity during HHFW heating, a substantial increase in stored energy and a sustained central electron temperature of 5-6 keV. Another focus of NSTX HHFW research is to heat an H-mode generated by 90 keV neutral beam injection (NBI). Improved HHFW coupling to NBI-generated H-modes has resulted in a broad increase in electron temperature profile when HHFW heating is applied. Analysis of a closely matched pair of NBI and HHFW+NBI H-mode plasmas revealed that about half of the antenna power is deposited inside the last closed flux surface (LCFS). Of the power damped inside the LCFS about two-thirds is absorbed directly by electrons and one-third accelerates fast-ions that are mostly promptly lost from the plasma. At longer toroidal launch wavelengths, HHFW+NBI H-mode plasmas can have an RF power flow to the divertor outside the LCFS that significantly reduces RF power deposition to the core. ELMs can also reduce RF power deposition to the core and increase power deposition to the edge. Recent full wave modeling of NSTX HHFW+NBI H-mode plasmas, with the model extended to the vessel wall, predicts a coaxial standing mode between the LCFS and the wall that can have large amplitudes at longer launch wavelengths. These simulation results qualitatively agree with HHFW
Okazaki, Yuji; Uno, Takanori; Asai, Hideki
In this paper, we propose an optimization system with parallel processing for reducing electromagnetic interference (EMI) on electronic control unit (ECU). We adopt simulated annealing (SA), genetic algorithm (GA) and taboo search (TS) to seek optimal solutions, and a Spice-like circuit simulator to analyze common-mode current. Therefore, the proposed system can determine the adequate combinations of the parasitic inductance and capacitance values on printed circuit board (PCB) efficiently and practically, to reduce EMI caused by the common-mode current. Finally, we apply the proposed system to an example circuit to verify the validity and efficiency of the system.
Complete bifurcation analysis of DC-DC converters under current mode control
Pikulin, D.
2014-03-01
The purpose of this research is to investigate to what extend application of novel method of complete bifurcation groups to the analysis of global dynamics of piecewise-smooth hybrid systems enables one to highlight new nonlinear effects before periodic and chaotic regimes. Results include the construction of complete one and two-parameter bifurcation diagrams, detection of various types of bifurcation groups and investigation of their interactions, localization of rare attractors, and the investigation of different principles of birth of chaotic attractors. Effectiveness of the approach is illustrated in respect to one of the most widely used switching systems-boost converter under current mode control operating in continuous current mode.
Stabilisation of ballooning modes in torsatrons with an externally applied toroidal current
Energy Technology Data Exchange (ETDEWEB)
Cooper, W.A. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)
1996-09-01
It has been found that ideal ballooning modes can impose very restrictive volume average {beta} limits in torsatrons much below the typical values close to 5% that are required to be economically realisable as reactor systems and it has been shown that externally applied toroidal currents that are peaked can destabilise the Mercier criterion in this type of configuration. We will show here that if the applied currents are hollow, they can stabilise the ballooning modes without triggering Mercier instabilities and as a result raise the limiting {beta}* from 2% to 5%. (author) 3 figs., 10 refs.
Current diffusive ballooning mode in a Tokamak with a noncircular cross section
Energy Technology Data Exchange (ETDEWEB)
Yagi, Masatoshi; Itoh, Sanae [Kyushu Univ., Kasuga, Fukuoka (Japan). Research Inst. for Applied Mechanics; Fukuyama, Atsushi; Itoh, Kimitaka
1997-02-01
The eigenvalue equation for the current diffusive ballooning mode in tokamaks is derived taking the geometrical effects, i.e., triangularity and ellipticity into account. The stability boundary is obtained in the strong ballooning limit. It is found that the ellipticity plays an important role on the stability of the current diffusive ballooning mode. On the other hand, the effect of the stabilization by the triangularity appears indirectly through the magnetic well term. The geometrical effect on the transport coefficient is also discussed. (author)
Current-Mode CMOS A/D Converter for pA to nA Input Currents
DEFF Research Database (Denmark)
Breten, Madalina; Lehmann, Torsten; Bruun, Erik
1999-01-01
. A prototype chip using the dual slope conversion method has been fabricated in a 0.7micron CMOS process. Experimental results from this converter are reported. Design problems and limitations of the converter are discussed and a new conversion technique providing a larger dynamic range and easy calibration......This paper describes a current mode A/D converter designed for a maximum input current range of 5nA and a resolution of the order of 1pA. The converter is designed for a potentiostat for amperometric chemical sensors and provides a constant polarization voltage for the measuring electrode...
Single-molecule electronics: Cooling individual vibrational modes by the tunneling current
Lykkebo, Jacob; Romano, Giuseppe; Gagliardi, Alessio; Pecchia, Alessandro; Solomon, Gemma C.
2016-03-01
Electronic devices composed of single molecules constitute the ultimate limit in the continued downscaling of electronic components. A key challenge for single-molecule electronics is to control the temperature of these junctions. Controlling heating and cooling effects in individual vibrational modes can, in principle, be utilized to increase stability of single-molecule junctions under bias, to pump energy into particular vibrational modes to perform current-induced reactions, or to increase the resolution in inelastic electron tunneling spectroscopy by controlling the life-times of phonons in a molecule by suppressing absorption and external dissipation processes. Under bias the current and the molecule exchange energy, which typically results in heating of the molecule. However, the opposite process is also possible, where energy is extracted from the molecule by the tunneling current. Designing a molecular "heat sink" where a particular vibrational mode funnels heat out of the molecule and into the leads would be very desirable. It is even possible to imagine how the vibrational energy of the other vibrational modes could be funneled into the "cooling mode," given the right molecular design. Previous efforts to understand heating and cooling mechanisms in single molecule junctions have primarily been concerned with small models, where it is unclear which molecular systems they correspond to. In this paper, our focus is on suppressing heating and obtaining current-induced cooling in certain vibrational modes. Strategies for cooling vibrational modes in single-molecule junctions are presented, together with atomistic calculations based on those strategies. Cooling and reduced heating are observed for two different cooling schemes in calculations of atomistic single-molecule junctions.
Pettersen, Klas H; Devor, Anna; Ulbert, Istvan; Dale, Anders M; Einevoll, Gaute T
2006-06-30
A new method for estimation of current-source density (CSD) from local field potentials is presented. This inverse CSD (iCSD) method is based on explicit inversion of the electrostatic forward solution and can be applied to data from multielectrode arrays with various geometries. Here, the method is applied to linear-array (laminar) electrode data. Three iCSD methods are considered: the CSD is assumed to have cylindrical symmetry and be (i) localized in infinitely thin discs, (ii) step-wise constant or (iii) continuous and smoothly varying (using cubic splines) in the vertical direction. For spatially confined CSD distributions the standard CSD method, involving a discrete double derivative, is seen in model calculations to give significant estimation errors when the lateral source dimension is comparable to the size of a cortical column (less than approximately 1 mm). Further, discontinuities in the extracellular conductivity are seen to potentially give sizable errors for even wider source distributions. The iCSD methods are seen to give excellent estimates when the correct lateral source dimension and spatial distribution of conductivity are incorporated. To illustrate the application to real data, iCSD estimates of stimulus-evoked responses measured with laminar electrodes in the rat somatosensory (barrel) cortex are compared to estimates from the standard CSD method.
Single-mode low threshold current multi-hole vertical-cavity surface-emitting lasers
Institute of Scientific and Technical Information of China (English)
Zhao Zhen-Bo; Xu Chen; Xie Yi-Yang; Zhou Kang; Liu Fa; Shen Guang-Di
2012-01-01
A multi-hole vertical-cavity surface-emitting laser (VCSEL) operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-reflector of an oxidationconfined 850 nm VCSEL.The single-mode output power of 2.6 mW,threshold current of 0.6 mA,full width of half maximum lasing spectrum of less than 0.1 nm,side mode suppression ratio of 28.4 dB,and far-field divergence angle of about 10° are obtained.The effects of different hole depths on the optical characteristics are simulated and analysed,including far-field divergence,spectrum and lateral cavity mode.The single-mode performance of this multi-hole device is attributed to the large radiation loss from the inter-hole spacing and the scattering loss at the bottom of the holes,particularly for higher order modes.
Current and Voltage Conveyors in Current- and Voltage-Mode Precision Full-Wave Rectifiers
Directory of Open Access Journals (Sweden)
J. Koton
2011-04-01
Full Text Available In this paper new versatile precision full-wave rectifiers using current and/or voltage conveyors as active elements and two diodes are presented. The performance of these circuit solutions is analysed and compared to the opamp based precision rectifier. To analyze the behavior of the functional blocks, the frequency dependent RMS error and DC transient value are evaluated for different values of input voltage amplitudes. Furthermore, experimental results are given that show the feasibilities of the conveyor based rectifiers superior to the corresponding operational amplifier based topology.
Effects of electron cyclotron current drive on the evolution of double tearing mode
Energy Technology Data Exchange (ETDEWEB)
Sun, Guanglan, E-mail: sunguanglan@nciae.edu.cn; Dong, Chunying [Basic Science Section, North China Institute of Aerospace Engineering, Langfang 065000 (China); Duan, Longfang [School of Computer and Remote Sensing Information Technology, North China Institute of Aerospace Engineering, Langfang 065000 (China)
2015-09-15
The effects of electron cyclotron current drive (ECCD) on the double tearing mode (DTM) in slab geometry are investigated by using two-dimensional compressible magnetohydrodynamics equations. It is found that, mainly, the double tearing mode is suppressed by the emergence of the secondary island, due to the deposition of driven current on the X-point of magnetic island at one rational surface, which forms a new non-complete symmetric magnetic topology structure (defined as a non-complete symmetric structure, NSS). The effects of driven current with different parameters (magnitude, initial time of deposition, duration time, and location of deposition) on the evolution of DTM are analyzed elaborately. The optimal magnitude or optimal deposition duration of driven current is the one which makes the duration of NSS the longest, which depends on the mutual effect between ECCD and the background plasma. Moreover, driven current introduced at the early Sweet-Parker phase has the best suppression effect; and the optimal moment also exists, depending on the duration of the NSS. Finally, the effects varied by the driven current disposition location are studied. It is verified that the favorable location of driven current is the X-point which is completely different from the result of single tearing mode.
Energy Technology Data Exchange (ETDEWEB)
Yang, Yuchen [State Key Lab for Materials Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Zhou, Xue [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Department of Electrical Engineering, Harbin Institute of Technology, Harbin 150000 (China); Liu, Jason X. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States); Anders, André, E-mail: aanders@lbl.gov [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States)
2016-01-18
We present evidence for breathing modes in magnetron sputtering plasmas: periodic axial variations of plasma parameters with characteristic frequencies between 10 and 100 kHz. A set of azimuthally distributed probes shows synchronous oscillations of the floating potential. They appear most clearly when considering the intermediate current regime in which the direction of azimuthal spoke motion changes. Breathing oscillations were found to be superimposed on azimuthal spoke motion. Depending on pressure and current, one can also find a regime of chaotic fluctuations and one of stable discharges, the latter at high current. A pressure-current phase diagram for the different situations is proposed.
A NOVEL HIGH PRECISION LOW POWER CURRENT MODE CMOS WINNER-TAKE-ALL CIRCUIT
Directory of Open Access Journals (Sweden)
K.L.Baishnab
2010-05-01
Full Text Available The design and simulation of winner-take –all Current Mode (WTA circuit is proposed. Inputs and outputs of the Circuits are current and voltage respectively, which makes the circuit appropriated forlow voltage neural hardware computation. The circuit was designed and simulated using Cadence gpdk090. The proposed novel current mode CMOS WTA operates at 0.7v with resolution of 0.001nA and a dynamic range from input current 10nA---1μA, which are much better than existing realizations. It is also observed that dynamic range can be raised further with increasing of power supply. Simulation results along withappropriate mathematical relations are reported.
Flip-Flops for accurate multiphase clocking: transmission gate versus current mode logic
Dutta, R.; Klumperink, Eric A.M.; Gao, X.; Ru, Z.; van der Zee, Ronan A.R.; Nauta, Bram
2013-01-01
Dynamic transmission gate (DTG) flip-flops (FFs) (DTG-FFs) and current mode logic (CML) FFs (CML-FFs) are compared targeting power efficient multiphase clock generation with low phase error. The effect of component mismatches on multiphase clock timing inaccuracies is modeled and compared, using the
Flip-Flops for accurate multiphase clocking: transmission gate versus current mode logic
Dutta, R.; Klumperink, E.A.M.; Gao, X.; Ru, Z.; Zee, van der R.A.R.; Nauta, B.
2013-01-01
Dynamic transmission gate (DTG) flip-flops (FFs) (DTG-FFs) and current mode logic (CML) FFs (CML-FFs) are compared targeting power efficient multiphase clock generation with low phase error. The effect of component mismatches on multiphase clock timing inaccuracies is modeled and compared, using the
16-Channel biphasic current-mode programmable charge balanced neural stimulation.
Li, Xiaoran; Zhong, Shunan; Morizio, James
2017-08-14
Neural stimulation is an important method used to activate or inhibit action potentials of the neuronal anatomical targets found in the brain, central nerve and peripheral nerve. The neural stimulator system produces biphasic pulses that deliver balanced charge into tissue from single or multichannel electrodes. The timing and amplitude of these biphasic pulses are precisely controlled by the neural stimulator software or imbedded algorithms. Amplitude mismatch between the anodic current and cathodic current of the biphasic pulse will cause permanently damage for the neural tissues. The main goal of our circuit and layout design is to implement a 16-channel biphasic current mode programmable neural stimulator with calibration to minimize the current mismatch caused by inherent complementary metal oxide semiconductor (CMOS) manufacturing processes. This paper presents a 16-channel constant current mode neural stimulator chip. Each channel consists of a 7-bit controllable current DAC used as sink and source current driver. To reduce the LSB quantization error and the current mismatch, an automatic calibration circuit and flow diagram is presented in this paper. There are two modes of operation of the stimulator chip-namely, stimulation mode and calibration mode. The chip also includes a digital interface used to control the stimulator parameters and calibration levels specific for each individual channel. This stimulator Application Specific Integrated Circuit (ASIC) is designed and fabricated in a 0.18 μm High-Voltage CMOS technology that allows for ±20 V power supply. The full-scale stimulation current was designed to be at 1 mA per channel. The output current was shown to be constant throughout the timing cycles over a wide range of electrode load impedances. The calibration circuit was also designed to reduce the effect of CMOS process variation of the P-channel metal oxide semiconductor (PMOS) and N-channel metal oxide semiconductor (NMOS) devices that will
A HIGH PERFORMANCE FULLY DIFFERENTIAL PURE CURRENT MODE OPERATIONAL AMPLIFIER AND ITS APPLICATIONS
Directory of Open Access Journals (Sweden)
SEYED JAVAD AZHARI
2012-08-01
Full Text Available In this paper a novel high performance all current-mode fully-differential (FD Current mode Operational Amplifier (COA in BIPOLAR technology is presented. The unique true current mode simple structure grants the proposed COA the largest yet reported unity gain frequency while providing low voltage low power operation. Benefiting from some novel ideas, it also exhibits high gain, high common mode rejection ratio (CMRR, high power supply rejection ratio (PSRR, high output impedance, low input impedance and most importantly high current drive capability. Its most important parameters are derived and its performance is proved by PSPICE simulations using 0.8 μm BICMOS process parameters at supply voltage of ±1.2V indicating the values of 82.4 dB,52.3º, 31.5 Ω, 31.78 MΩ, 179.2 dB, 2 mW and 698 MHz for gain, phase margin, input impedance, output impedance, CMRR, power and unity gain frequency respectively. Its CMRR also shows very high frequency of 2.64 GHz at zero dB. Its very high PSRR+/PSRR- of 182 dB/196 dB makes the proposed COA a highly suitable block in Mixed-Mode (SOC chips. Most favourably it can deliver up to ±1.5 mA yielding a high current drive capability exceeding 25. To demonstrate the performance of the proposed COA, it is used to realize a constant bandwidth voltage amplifier and a high performance Rm amplifier.
A differential low-voltage high gain current-mode integrated RF receiver front-end
Chunhua, Wang; Minglin, Ma; Jingru, Sun; Sichun, Du; Xiaorong, Guo; Haizhen, He
2011-02-01
A differential low-voltage high gain current-mode integrated RF front end for an 802.11b WLAN is proposed. It contains a differential transconductance low noise amplifier (Gm-LNA) and a differential current-mode down converted mixer. The single terminal of the Gm-LNA contains just one MOS transistor, two capacitors and two inductors. The gate-source shunt capacitors, Cx1 and Cx2, can not only reduce the effects of gate-source Cgs on resonance frequency and input-matching impedance, but they also enable the gate inductance Lg1,2 to be selected at a very small value. The current-mode mixer is composed of four switched current mirrors. Adjusting the ratio of the drain channel sizes of the switched current mirrors can increase the gain of the mixer and accordingly increase the gain of RF receiver front-end. The RF front-end operates under 1 V supply voltage. The receiver RFIC was fabricated using a chartered 0.18 μm CMOS process. The integrated RF receiver front-end has a measured power conversion gain of 17.48 dB and an input referred third-order intercept point (IIP3) of -7.02 dBm. The total noise figure is 4.5 dB and the power is only 14 mW by post-simulations.
A double-stage start-up structure to limit the inrush current used in current mode charge pump
Cong, Liu; Xinquan, Lai; Hanxiao, Du; Yuan, Chi
2016-06-01
A double-stage start-up structure to limit the inrush current used in current-mode charge pump with wide input range, fixed output and multimode operation is presented in this paper. As a widely utilized power source implement, a Li-battery is always used as the power supply for chips. Due to the internal resistance, a potential drop will be generated at the input terminal of the chip with an input current. A false shut down with a low supply voltage will happen if the input current is too large, leading to the degradation of the Li-battery's service life. To solve this problem, the inrush current is limited by introducing a new start-up state. All of the circuits have been implemented with the NUVOTON 0.6 μm CMOS process. The measurement results show that the inrush current can be limited below 1 A within all input supply ranges, and the power efficiency is higher than the conventional structure. Project supported by the National Natural Science Foundation of China (No. 61106026).
Enhancement-mode InAlN/GaN MISHEMT with low gate leakage current
Institute of Scientific and Technical Information of China (English)
Gu Guodong; Cai Yong; Feng Zhihong; Liu Bo; Zeng Chunhong; Yu Guohao; Dong Zhihua; Zhang Baoshun
2012-01-01
We report an enhancement-mode InAlN/GaN MISHEMT with a low gate leakage current by a thermal oxidation technique under gate.The off-state source-drain current density is as low as ～10-7 A/mm at VGs =0 V and VDS =5 V.The threshold voltage is measured to be +0.8 V by linear extrapolation from the transfer characteristics.The E-mode device exhibits a peak transconductance of 179 mS/mm at a gate bias of 3.4 V.A low reverse gate leakage current density of 4.9 × 10-7 A/mm is measured at VGS =-15 V.
Effort of lower hybrid current drive experiments toward to H-mode in EAST
Ding, B. J.; Li, M. H.; Liu, F. K.; Shan, J. F.; Li, Y. C.; Wang, M.; Liu, L.; Zhao, L. M.; Yang, Y.; Wu, Z. G.; Feng, J. Q.; Hu, H. C.; Jia, H.; Cheng, M.; Zang, Q.; Lyu, B.; Duan, Y. M.; Lin, S. Y.; Wu, J. H.; Hillairet, J.; Ekedahl, A.; Peysson, Y.; Goniche, M.; Tuccillo, A. A.; Cesario, R.; Amicucci, L.; Shen, B.; Gong, X. Z.; Xu, G. S.; Zhao, H. L.; Hu, L. Q.; Li, J. G.; Wan, B. N.; EAST Team
2017-02-01
Lower hybrid current drive (LHCD) is an effective tool to achieve high confinement (H-mode) plasma in EAST. To utilize LHCD for accessing H-mode plasma, efforts have been made to improve LHW (lower hybrid wave)-plasma coupling and current drive capability at high density. Improved LHW-plasma coupling by means of local gas puffing and gas puffing from the electron side is routinely used during EAST operation with LHCD. High density experiments suggest that low recycling and high LH frequency are preferred for LHCD experiments at high density, consistent with previous results in other machines. The effect of LHCD on the current profile in EAST demonstrates that it is possible to control the plasma profile by optimizing the LHW spectrum. Repeatable H-mode plasma was obtained by LHCD and the maximum density during H-mode with the combination of 2.45 GHz and 4.6 GHz LH waves was up to 4.5 × 1019 m-3.
The impact of the AEC mode of tube current on the dose at CT scans
Energy Technology Data Exchange (ETDEWEB)
Moon, Il Bong; Dong, Kyung Rae [Dept. of Radiological Technology, Gwangju Health University, Gwangju (Korea, Republic of); Kim, Kwang Cheol [Dept. of of Nuclear Engineering, Chosun University,Gwangju (Korea, Republic of)
2016-11-15
In this study, the automatic exposure control (AEC) modes of tube current (SIEMENSCare Dose 4D and GE AEC mode) that CT manufacturers are using was applied to neck, chest and abdomen in order to determine the difference in the respective dose parameters (CTDIvol, DLP and mSv) resulting from the dose reduction. Equipment in use at C university adopted Care Dose 4D of Siemens and AEC mode of General Electric (GE), and the x-ray exposure conditions were adjusted to be as identical as possible between the experiments. For the assessment of the dose reduction, the differences between the doses with and without the use of the tube current AEC mode by the respective manufacturer were measured for each body part including neck, chest and abdomen of a human phantom, Rando Phantom (Art-200x, Fluke Biomedical, USA). First, the assessment of SIEMENS-Care Dose 4D yielded the following results. At the neck, the automatic exposure control resulted in a 3.3% reduction in CTDIvol and DLP, and a 3% reduction in the effective dose, mSv, compared to manual exposure control. The automatic exposure control at the chest displayed the reduction in CTDIvol and DLP by 25.5%, and in the effective dose, mSv, by 25.4% compared to the manual exposure control. In case of abdomen, CTDIvol and DLP were shown to be reduced by 16%, and the effective dose (mSv) by 16.3% under the automatic exposure control compared to the manual exposure. Second, the assessment results of GE AEC mode are as follows. The automatic exposure control at the neck resulted in a 45.1% reduction in CTDIvol and DLP, and a 44.7% reduction in the effective dose (mSv) in comparison to the manual exposure control. At the chest, the automatic exposure control displayed a 47.6% reduction in CTDIvol and DLP, and a 47.5% reduction in the effective dose, mSv, compared to the manual exposure control. At the abdomen, it was shown that CTDIvol and DLP were reduced by 26.9%, and the effective dose (mSv) by 26.8% under the automatic
Explosive Magnetic Reconnection in Double-current Sheet Systems: Ideal versus Resistive Tearing Mode
Baty, Hubert
2017-03-01
Magnetic reconnection associated with the tearing instability occurring in double-current sheet systems is investigated within the framework of resistive magnetohydrodynamics (MHD) in a two-dimensional Cartesian geometry. A special emphasis on the existence of fast and explosive phases is taken. First, we extend the recent theory on the ideal tearing mode of a single-current sheet to a double-current layer configuration. A linear stability analysis shows that, in long and thin systems with (length to shear layer thickness) aspect ratios scaling as {S}L9/29 (S L being the Lundquist number based on the length scale L), tearing modes can develop on a fast Alfvénic timescale in the asymptotic limit {S}L\\to ∞ . The linear results are confirmed by means of compressible resistive MHD simulations at relatively high S L values (up to 3× {10}6) for different current sheet separations. Moreover, the nonlinear evolution of the ideal double tearing mode (IDTM) exhibits a richer dynamical behavior than its single-tearing counterpart, as a nonlinear explosive growth violently ends up with a disruption when the two current layers interact trough the merging of plasmoids. The final outcome of the system is a relaxation toward a new state, free of magnetic field reversal. The IDTM dynamics is also compared to the resistive double tearing mode dynamics, which develops in similar systems with smaller aspect ratios, ≳ 2π , and exhibits an explosive secondary reconnection, following an initial slow resistive growth phase. Finally, our results are used to discuss the flaring activity in astrophysical magnetically dominated plasmas, with a particular emphasis on pulsar systems.
Design and implementation of adaptive slope compensation in current mode DC-DC converter
Energy Technology Data Exchange (ETDEWEB)
Guo Zhongjie; Wu Longsheng; Liu Youbao, E-mail: guozhongjie4213@126.com [Xi' an Microelectronic Technology Institute, Xi' an 710054 (China)
2010-12-15
To improve the compensation for the inherent instability in a current mode converter, the adaptive slope compensation, giving attention to the problems of the traditional compensation on compensation accuracy, loading capability and turning jitter, is presented. Based on the analysis of current loop, by detecting the input and output voltage, converting the adaptive slope compensation current, the compensation of the current loop is optimized successfully. It can not only improve the compensation accuracy but also eliminate the over compensation, the turning jitter and the poor loading capability in the reported slope compensation. A power supply chip with adaptive slope compensation has been fabricated in a 0.35 {mu}m CMOS process. The measurement results show that the chip starts up and operates steadily with the constant current limit under conditions of 5 V input voltage, from 10% to 100% duty cycle. (semiconductor integrated circuits)
MISO Current-mode Biquad Filter with Independent Control of Pole Frequency and Quality Factor
Directory of Open Access Journals (Sweden)
W. Jaikla
2012-09-01
Full Text Available This article presents a three-inputs single-output biquadratic filter performing completely standard functions: low-pass, high-pass, band-pass, band-reject and all-pass functions, based on current controlled current conveyor transconductance amplifier (CCCCTA. The quality factor and pole frequency can be electronically/independently tuned via the input bias current. The proposed circuit uses 2 CCCCTAs and 2 grounded capacitors without external any resistors which is very suitable to further develop into an integrated circuit. The filter does not require double input current signal. Each function response can be selected by suitably selecting input signals with digital method. Moreover, the circuit possesses high output impedance which would be an ideal choice for current-mode cascading. The PSPICE simulation results are included to verify the workability of the proposed filter. The given results agree well with the theoretical anticipation.
Self-amplified CMOS image sensor using a current-mode readout circuit
Santos, Patrick M.; de Lima Monteiro, Davies W.; Pittet, Patrick
2014-05-01
The feature size of the CMOS processes decreased during the past few years and problems such as reduced dynamic range have become more significant in voltage-mode pixels, even though the integration of more functionality inside the pixel has become easier. This work makes a contribution on both sides: the possibility of a high signal excursion range using current-mode circuits together with functionality addition by making signal amplification inside the pixel. The classic 3T pixel architecture was rebuild with small modifications to integrate a transconductance amplifier providing a current as an output. The matrix with these new pixels will operate as a whole large transistor outsourcing an amplified current that will be used for signal processing. This current is controlled by the intensity of the light received by the matrix, modulated pixel by pixel. The output current can be controlled by the biasing circuits to achieve a very large range of output signal levels. It can also be controlled with the matrix size and this permits a very high degree of freedom on the signal level, observing the current densities inside the integrated circuit. In addition, the matrix can operate at very small integration times. Its applications would be those in which fast imaging processing, high signal amplification are required and low resolution is not a major problem, such as UV image sensors. Simulation results will be presented to support: operation, control, design, signal excursion levels and linearity for a matrix of pixels that was conceived using this new concept of sensor.
Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode.
Poehlmann, Flavio R; Cappelli, Mark A; Rieker, Gregory B
2010-12-01
Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma deflagration. The effects of varying the bank capacitance, transmission line inductance, and applied electrode voltage were studied over the range from 14 to 112 μF, 50 to 200 nH, and 1 to 3 kV, respectively.
Murphy, G C; Pelletier, Guy
2008-01-01
Magnetic reconnection plays a critical role in many astrophysical processes where high energy emission is observed, e.g. particle acceleration, relativistic accretion powered outflows, pulsar winds and probably in dissipation of Poynting flux in GRBs. The magnetic field acts as a reservoir of energy and can dissipate its energy to thermal and kinetic energy via the tearing mode instability. We have performed 3d nonlinear MHD simulations of the tearing mode instability in a current sheet. Results from a temporal stability analysis in both the linear regime and weakly nonlinear (Rutherford) regime are compared to the numerical simulations. We observe magnetic island formation, island merging and oscillation once the instability has saturated. The growth in the linear regime is exponential in agreement with linear theory. In the second, Rutherford regime the island width grows linearly with time. We find that thermal energy produced in the current sheet strongly dominates the kinetic energy. Finally preliminary ...
Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode
Poehlmann, Flavio R.; Cappelli, Mark A.; Rieker, Gregory B.
2010-12-01
Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma deflagration. The effects of varying the bank capacitance, transmission line inductance, and applied electrode voltage were studied over the range from 14 to 112 μF, 50 to 200 nH, and 1 to 3 kV, respectively.
Energy Resolution of Large Area Current-mode Si-PIN Detector
Institute of Scientific and Technical Information of China (English)
SU; Dan; ZHANG; Guo-guang; WANG; Guo-bao
2013-01-01
Large area current-mode Si-PIN detector is fabricated by adopting planar technology.Diameter are ?20 mm,?50 mm,?60 mm,and thickness is 300μm.Energy resolution and peak position of 226Ra-αparticles are measured in the vacuum chamber.The peak energy of the 226Ra-αparticle is 4 784.4,5 304.5,
Zhang, Shuangxi
2014-01-01
The past studies treated the perturbed distribution of circulating electrons as adiabatic one when studying the dispersion relation of electrostatic geodesic acoustic mode(GAM). In this paper, the flow of electron geodesic current (FEGC) is added to modify this adiabatic distribution. Based on the drift kinetic theory, it is found that FEGC obviously increases the magnitude of the standard GAM's frequency and reduces its damping rate. The increase of frequency results from the contribution of...
PRIMARY SIDE DETECTION AND PEAK CURRENT MODE CONTROL IN FLYBACK CONVERTER
Institute of Scientific and Technical Information of China (English)
Fang Jian; Lu Zhiping; Yang Jian; Li Zhaoji
2004-01-01
A new cycle-by-cycle control flyback converter with primary side detection and peak current mode control is proposed and its dynamic characteristics are analyzed. The flyback converter is verified by the OrCAD simulator. The main advantages of this converter over the conventional one are simplicity, small size, rapid regulating and no sensing control signals over the isolation barrier. The circuit is suitable for digital control implementations.
Current Sensor Fault Diagnosis Based on a Sliding Mode Observer for PMSM Driven Systems.
Huang, Gang; Luo, Yi-Ping; Zhang, Chang-Fan; Huang, Yi-Shan; Zhao, Kai-Hui
2015-05-11
This paper proposes a current sensor fault detection method based on a sliding mode observer for the torque closed-loop control system of interior permanent magnet synchronous motors. First, a sliding mode observer based on the extended flux linkage is built to simplify the motor model, which effectively eliminates the phenomenon of salient poles and the dependence on the direct axis inductance parameter, and can also be used for real-time calculation of feedback torque. Then a sliding mode current observer is constructed in αβ coordinates to generate the fault residuals of the phase current sensors. The method can accurately identify abrupt gain faults and slow-variation offset faults in real time in faulty sensors, and the generated residuals of the designed fault detection system are not affected by the unknown input, the structure of the observer, and the theoretical derivation and the stability proof process are concise and simple. The RT-LAB real-time simulation is used to build a simulation model of the hardware in the loop. The simulation and experimental results demonstrate the feasibility and effectiveness of the proposed method.
Current Sensor Fault Diagnosis Based on a Sliding Mode Observer for PMSM Driven Systems
Directory of Open Access Journals (Sweden)
Gang Huang
2015-05-01
Full Text Available This paper proposes a current sensor fault detection method based on a sliding mode observer for the torque closed-loop control system of interior permanent magnet synchronous motors. First, a sliding mode observer based on the extended flux linkage is built to simplify the motor model, which effectively eliminates the phenomenon of salient poles and the dependence on the direct axis inductance parameter, and can also be used for real-time calculation of feedback torque. Then a sliding mode current observer is constructed in αβ coordinates to generate the fault residuals of the phase current sensors. The method can accurately identify abrupt gain faults and slow-variation offset faults in real time in faulty sensors, and the generated residuals of the designed fault detection system are not affected by the unknown input, the structure of the observer, and the theoretical derivation and the stability proof process are concise and simple. The RT-LAB real-time simulation is used to build a simulation model of the hardware in the loop. The simulation and experimental results demonstrate the feasibility and effectiveness of the proposed method.
New Squarer Circuits and a Current-Mode Full-Wave Rectifier Topology Suitable for Integration
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S. Minaei
2010-12-01
Full Text Available In this paper, three squarer configurations and a current-mode (CM full-wave rectifier circuit are suggested. The first and second squarer configurations respectively use two PMOS and two NMOS transistors while the third one employs three PMOS and one NMOS transistors. A CM full-wave rectifier with high output impedance current is developed. All of the proposed circuits provide several advantages such as low number of components and less power consumption. The proposed circuits are simulated using SPICE program to demonstrate their performance and workability.
New Voltage-Mode All-pass Filter Topology Employing Single Current Operational Amplifier
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Hasan Çiçekli
2016-02-01
Full Text Available In this paper, a new voltage-mode all-pass filter topology based on single current operational amplifier (COA and the implementation of COA by using current conveyors are presented. The proposed topology employs three admittances and single active circuit element. COA implementation by using current conveyor blocks as sub-circuit contributes to workability of the COA employing circuits by using commercially available integrated circuits that can be employed as current conveyor. The validity of the proposed filter is verified by PSPICE simulation programme by using the MOSIS 0.35 micron CMOS process parameters. The simulation results agree well with the theoretical analysis and the circuit achieve a good total harmonic distortion (THD performance.
A Current-mode Electronically Controllable Multifunction Biquadratic Filter Using CCCIIs
Directory of Open Access Journals (Sweden)
MONTREE SIRIPRUCHYANUN
2013-03-01
Full Text Available This article presents a current-mode multifunction biquadratic filter performing completely standard functions low-pass, high-pass, band-pass, band-reject and all-pass functions. The circuit principle is based on second-generation current-controlled current conveyor (CCCII with three input terminals and one output terminal. The features of the circuit are that, the pole frequency can be electronically tuned via the input bias currents. The circuit topology is very simple, consisting of merely 2 CCCIIs and 2 grounded capacitors. Without any external resistor and using only grounded elements, the proposed circuit is very comfortable to further develop into an integrated circuit architecture. The PSpice simulation results are shown. The given results agree well with the theoretical anticipation. The total power consumption is approximately 1.87mW at ±1.5V power supply voltages.
On the merits of heating and current drive for tearing mode stabilization
DeLazzari, D.; Westerhof, E.
2009-07-01
Neoclassical tearing modes (NTMs) are magnetohydrodynamic modes that can limit the performance of high β discharges in a tokamak, leading eventually to a plasma disruption. A NTM is sustained by the perturbation of the 'bootstrap' current, which is a consequence of the pressure flattening across a magnetic island. Control and suppression of this mode can be achieved by means of electron cyclotron waves (ECWs) which allow the deposition of highly localized power at the island location. The ECW power replenishes the missing bootstrap current by generating a current perturbation either inductively, through a temperature perturbation (electron cyclotron resonance heating), or non-inductively by direct current drive (electron cyclotron current drive). Although both methods have been applied successfully to experiments showing a predominance of ECRH for medium-sized limiter tokamaks (TEXTOR, T-10) and of ECCD for mid-to-large-sized divertor tokamaks (AUG, DIII-D, JT-60), conditions determining their relative importance are still unclear. We address this problem with a numerical study focused on the contributions of heating and current drive to the temporal evolution of NTMs as described by the modified Rutherford equation. For the effects of both heating as well as current drive, simple analytical expressions have been found in terms of an efficiency fore-factor times a 'geometrical' term depending on the power deposition width wdep, location and modulation. When the magnetic island width w equals the width of the deposition profile, w ≈ wdep, both geometric terms are practically identical. Whereas for current drive the geometric term approaches a constant for small island widths and is inversely proportional to (w/wdep)2 for large island widths, the heating term approaches a constant for large island widths and is proportional to (w/wdep) for small island widths. For medium-sized tokamaks (TEXTOR, AUG) the heating and current drive efficiencies are of the same order
Discontinuous symplectic capacities
Zehmisch, K.; Ziltener, F.J.
2014-01-01
We show that the spherical capacity is discontinuous on a smooth family of ellipsoidal shells. Moreover, we prove that the shell capacity is discontinuous on a family of open sets with smooth connected boundaries.
Bifurcation and chaos in high-frequency peak current mode Buck converter
Chang-Yuan, Chang; Xin, Zhao; Fan, Yang; Cheng-En, Wu
2016-07-01
Bifurcation and chaos in high-frequency peak current mode Buck converter working in continuous conduction mode (CCM) are studied in this paper. First of all, the two-dimensional discrete mapping model is established. Next, reference current at the period-doubling point and the border of inductor current are derived. Then, the bifurcation diagrams are drawn with the aid of MATLAB. Meanwhile, circuit simulations are executed with PSIM, and time domain waveforms as well as phase portraits in i L-v C plane are plotted with MATLAB on the basis of simulation data. After that, we construct the Jacobian matrix and analyze the stability of the system based on the roots of characteristic equations. Finally, the validity of theoretical analysis has been verified by circuit testing. The simulation and experimental results show that, with the increase of reference current I ref, the corresponding switching frequency f is approaching to low-frequency stage continuously when the period-doubling bifurcation happens, leading to the converter tending to be unstable. With the increase of f, the corresponding I ref decreases when the period-doubling bifurcation occurs, indicating the stable working range of the system becomes smaller. Project supported by the National Natural Science Foundation of China (Grant No. 61376029), the Fundamental Research Funds for the Central Universities, China, and the College Graduate Research and Innovation Program of Jiangsu Province, China (Grant No. SJLX15_0092).
A Zero Input Current Ripple ZVS/ZCS Boost Converter with Boundary-Mode Control
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Ching-Ming Lai
2014-10-01
Full Text Available In this paper, in order to achieve zero ripple conditions, the use of a ripple mirror (RM circuit for the boost converter is proposed. The operation modes are studied and steady-state analyses performed to show the merits of the proposed converter. It is found that the proposed RM circuit technique can provide much better flexibility than the two-phase interleaved boost converter for locating the zero ripple operating point in the design stage. In addition, the choice of using a boundary-mode control is mainly based on the consideration of achieving both ZVS (zero voltage switching/ZCS (zero current switching soft-switching and constant on-time control for the converter. To verify the performance of the proposed converter, a 48 V input and 200 W/200 V output prototype is constructed. Experimental results verify the effectiveness of the proposed converter.
Light-front projection of spin-1 electromagnetic current and zero-modes
Energy Technology Data Exchange (ETDEWEB)
Melo, J.P.B.C. de [Laboratorio de Fisica Teorica e Computacao Cientifica - LFTC, Universidade Cruzeiro do Sul, 01506-000 Sao Paulo, SP (Brazil); Frederico, T., E-mail: tobias@ita.br [Instituto Tecnologico de Aeronautica, DCTA, 12.228-900 Sao Jose dos Campos, SP (Brazil)
2012-02-14
The issue of the contribution of zero-modes to the light-front projection of the electromagnetic current of phenomenological models of vector particles vertices is addressed in the Drell-Yan frame. Our analytical model of the Bethe-Salpeter amplitude of a spin-1 fermion-antifermion composite state gives a physically motivated light-front wave function symmetric by the exchange of the fermion and antifermion, as in the {rho}-meson case. We found that among the four independent matrix elements of the plus component in the light-front helicity basis only the 0{yields}0 one carries zero-mode contributions. Our derivation generalizes to symmetric models, important for applications, the above conclusion found for a simplified non-symmetrical form of the spin-1 Bethe-Salpeter amplitude with photon-fermion point-like coupling and also for a smeared fermion-photon vertex model.
Light-Front projection of spin-1 electromagnetic current and zero-modes
de Melo, J P B C; 10.1016/j.physletb.2012.01.021
2012-01-01
The issue of the contribution of zero-modes to the light-front projection of the electromagnetic current of phenomenological models of vector particles vertices is addressed in the Drell-Yan frame. Our analytical model of the Bethe-Salpeter amplitude of a spin-1 fermion-antifermion composite state gives a physically motivated light-front wave function symmetric by the exchange of the fermion and antifermion, as in the $\\rho$-meson case. We found that among the four independent matrix elements of the plus component in the light-front helicity basis only the $0\\to 0$ one carries zero mode contributions. Our derivation generalizes to symmetric models, important for applications, the above conclusion found for a simplified non-symmetrical form of the spin-1 Bethe-Salpeter amplitude with photon-fermion point-like coupling and also for a smeared fermion-photon vertex model.
Pixelated Geiger-Mode Avalanche Photo-Diode Characterization through Dark Current Measurement
Amaudruz, Pierre-André; Gilhully, Colleen; Goertzen, Andrew; James, Lloyd; Kozlowski, Piotr; Retière, Fabrice; Shams, Ehsan; Sossi, Vesna; Stortz, Greg; Thiessen, Jonathan D; Thompson, Christopher J
2013-01-01
PIXELATED geiger-mode avalanche photodiodes(PPDs), often called silicon photomultipliers (SiPMs) are emerging as an excellent replacement for traditional photomultiplier tubes (PMTs) in a variety of detectors, especially those for subatomic physics experiments, which requires extensive test and operation procedures in order to achieve uniform responses from all the devices. In this paper, we show for two PPD brands, Hamamatsu MPPC and SensL SPM, that the dark noise rate, breakdown voltage and rate of correlated avalanches can be inferred from the sole measure of dark current as a function of operating voltage, hence greatly simplifying the characterization procedure. We introduce a custom electronics system that allows measurement for many devices concurrently, hence allowing rapid testing and monitoring of many devices at low cost. Finally, we show that the dark current of Hamamastu Multi-Pixel Photon Counter (MPPC) is rather independent of temperature at constant operating voltage, hence the current measure...
Current control of 6-phases 100kW interleaved buck/boost converter for railway application
2009-01-01
The purpose of this paper is to present a 6-phases interleaved buck-boost converter of 100kW de-signed for a hybrid locomotive. The IGBT’s are working partially in continuous and discontinuous con-duction mode. Experiments show the effectiveness of the digital current control, current sharing and discontinuous-continuous transition with only one current sensor
Directory of Open Access Journals (Sweden)
M. Kumngern
2013-06-01
Full Text Available This paper presents two low-power voltage-mode multifunction biquadratic filters using differential difference current conveyors. Each proposed circuit employs three differential difference current conveyors, two grounded capacitors and two grounded resistors. The low-voltage ultra-low-power differential difference current conveyor is used to provide low-power consumption of the proposed filters. By appropriately connecting the input and output terminals, the proposed filters can provide low-pass, band-pass, high-pass, band-stop and all-pass voltage responses at high-input terminals, which is a desirable feature for voltage-mode operations. The natural frequency and the quality factor can be orthogonally set by adjusting the circuit components. For realizing all the filter responses, no inverting-type input signal requirements as well as no component-matching conditional requirements are imposed. The incremental parameter sensitivities are also low. The characteristics of the proposed circuits are simulated by using PSPICE simulators to confirm the presented theory.
Implementations of artificial neural networks using current-mode pulse width modulation technique.
El-Masry, E I; Yang, H K; Yakout, M A
1997-01-01
The use of a current-mode pulse width modulation (CM-PWM) technique to implement analog artificial neural networks (ANNs) is presented. This technique can be used to efficiently implement the weighted summation operation (WSO) that are required in the realization of a general ANN. The sigmoidal transformation is inherently performed by the nonlinear transconductance amplifier, which is a key component in the current integrator used in the realization of WSO. The CM-PWM implementation results in a minimum silicon area, and therefore is suitable for very large scale neural systems. Other pronounced features of the CM-PWM implementation are its easy programmability, electronically adjustable gains of neurons, and modular structures. In this paper, all the current-mode CMOS circuits (building blocks) required for the realization of CM-PWM ANNs are presented and simulated. Four modules for modular design of ANNs are introduced. Also, it is shown that the CM-PWM technique is an efficient method for implementing discrete-time cellular neural networks (DT-CNNs). Two application examples are given: a winner-take-all circuit and a connected component detector.
A CMOS current-mode log(x) and log(1/x) functions generator
Al-Absi, Munir A.; Al-Tamimi, Karama M.
2014-08-01
A novel Complementary Metal Oxide Semiconductor (CMOS) current-mode low-voltage and low-power controllable logarithmic function circuit is presented. The proposed design utilises one Operational Transconductance Amplifier (OTA) and two PMOS transistors biased in weak inversion region. The proposed design provides high dynamic range, controllable amplitude, high accuracy and is insensitive to temperature variations. The circuit operates on a ±0.6 V power supply and consumes 0.3 μW. The functionality of the proposed circuit was verified using HSPICE with 0.35 μm 2P4M CMOS process technology.
Dependency of Tearing Mode Stability on Current and Pressure Profiles in DIII-D Hybrid Discharges
Kim, K.; Park, J. M.; Murakami, M.; La Haye, R. J.; Na, Y.-S.; SNU/ORAU; ORNL; Atomics, General; SNU; DIII-D Team
2016-10-01
Understanding the physics of the onset and evolution of tearing modes (TMs) in tokamak plasmas is important for high- β steady-state operation. Based on DIII-D steady-state hybrid experiments with accurate equilibrium reconstruction and well-measured plasma profiles, the 2/1 tearing mode can be more stable with increasing local current and pressure gradient at rational surface and with lower pressure peaking and plasma inductance. The tearing stability index Δ', estimated by the Rutherford equation with experimental mode growth rate was validated against Δ' calculated by linear eigenvalue solver (PEST3); preliminary comprehensive MHD modeling by NIMROD reproduced the TM onset reasonably well. We present a novel integrated modeling for the purpose of predicting TM onset in experiment by combining a model equilibrium reconstruction using IPS/FASTRAN, linear stability Δ' calculation using PEST3, and fitting formula for critical Δ' from NIMROD. Work supported in part by the US DoE under DE-AC05-06OR23100, DE-AC05-00OR22725, and DEFC02-04ER54698.
Pratt, J; Westerhof, E
2016-01-01
When electron cyclotron (EC) driven current is first applied to the inside of a magnetic island, the current spreads throughout the island and after a short period achieves a steady level. Using a two equation fluid model for the EC current that allows us to examine this early evolution in detail, we analyze high-resolution simulations of a 2/1 classical tearing mode in a low-beta large aspect-ratio circular tokamak. These simulations use a nonlinear 3D reduced-MHD fluid model and the JOREK code. During the initial period where the EC driven current grows and spreads throughout the magnetic island, it is not a function of the magnetic flux. However, once it has reached a steady-state, it should be a flux function. We demonstrate numerically that if sufficiently resolved toroidally, the steady-state EC driven current becomes approximately a flux function. We discuss the physics of this early period of EC evolution and its impact on the size of the magnetic island.
Characteristics of persistent-current mode of HTS coil on superconducting electromagnet
Energy Technology Data Exchange (ETDEWEB)
Lee, C.Y., E-mail: cylee@krri.re.kr [Korea Railroad Research Institute, Woram Dong, Uiwang Si 437-757 (Korea, Republic of); Kim, J.; Han, Y.J.; Kang, B. [Korea Railroad Research Institute, Woram Dong, Uiwang Si 437-757 (Korea, Republic of); Chung, Y.D. [Department of Electrical Engineering, Suwon University, Bongdang Eup, Hwaseong Si 445-743 (Korea, Republic of); Yoon, Y.S. [Department of Electrical Engineering, Ansan College of Technology, Choji-Dong, Ansan Si 425-792 (Korea, Republic of); Chu, S.Y.; Hwang, Y.J.; Jo, H.C.; Jang, J.Y.; Ko, T.K. [Department of Electrical and Electronic Engineering, Yonsei University, Sinchon-dong, Seoul 120-749 (Korea, Republic of)
2011-11-15
The levitation gap of an electromagnetic suspension (EMS) system affects the current decay rate of superconducting electromagnet. The presence of iron core provides a significant benefit in the PCM performance of SC coil. The increased levitation gap of the EMS model with the SC-EM could negatively affect the design of SC-EM operated in PCM. This paper investigates the way in which the levitation gap of an electromagnetic suspension (EMS) system affects the current decay rate of superconducting electromagnet (SC-EM) operated in persistence-current mode (PCM). Using inductance analyzed from the magnetic circuit of an EMS model, the current decay rate caused by the variation in the levitation gap was simulated. In order to experimentally verify the simulation results, we fabricated a small-scale EMS model with SC coil operated in PCM and measured the current decay rates at different levitation gaps. The result showed that the presence of iron core provides a significant benefit in the PCM performance of SC coil, but the benefit decreased as the levitation gap increases. This study revealed that the increased levitation gap of the EMS model with the SC-EM could negatively affect the design of SC-EM operated in PCM.
New Current-Mode Bandpass Filters Using Three Single-Output ICCIIs
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Ahmed M. Soliman
2007-11-01
Full Text Available New current-mode bandpass filters using three single outputs inverting second generation current conveyors (ICCII are introduced. The first circuit uses two ICCII+ and one ICCIIÃ¢ÂˆÂ’, and realizes an inverting bandpass response. This circuit has one floating resistor and no independent gain control. The second circuit uses three ICCIIÃ¢ÂˆÂ’ and realizes a noninverting bandpass response. The third circuit uses three ICCII+ and realizes also a noninverting bandpass response. The second and third circuits employ four grounded resistors and two grounded capacitors and have independent control on Q and on the center frequency gain by varying a single grounded resistor. Spice simulation results using 0.5Ã¢Â€Â‰um CMOS transistors are included to support the theoretical analysis.
Advanced Readout System IC Current Mode Semi-Gaussian Shapers Using CCIIs and OTAs
Directory of Open Access Journals (Sweden)
Thomas Noulis
2007-01-01
Full Text Available Novel CMOS current mode shapers for front-end electronics are proposed. In particular, six semi-Gaussian shaper implementations based on second generation current conveyors and operational transconductance amplifiers are designed using advanced filter design techniques. Although all shaper architectures are fully integrated, they satisfy a relatively large peaking time. The topologies are analytically compared in terms of noise performance, power consumption, total harmonic distortion (THD, and dynamic range (DR in order to examine which is the most preferable in readout applications. Design technique selection criteria are proposed in relation to the shaper structures performance. Analysis is supported by simulations results using SPICE in a 0.6 μm process by Austria Mikro Systeme (AMS.
Second-Order Resonant Interaction of Ring Current Protons with Whistler-Mode Waves
Institute of Scientific and Technical Information of China (English)
XIAO Fu-Liang; CHEN Liang-Xu; HE Hui-Yong; ZHOU Qing-Hua
2008-01-01
We present a study on the second-order resonant interaction between the ring current protons with Whistler-mode waves propagating near the quasi electrostatic limit following the previous second-order resonant theory.The diffusion coefficients are proportional to the electric field amplitude E,much greater than those for the regular first-order resonance.which are proportional to the electric field amplitudes square E2.Numerical calculations for the pitch angle scattering are performed for typical energies of protons Ek=50ke V and 100ke V at locations L=2 and L=3.5.The timescale for the loss process of protons by the Whistler waves is found to approach one hour,comparable to that by the EMIC waves,suggesting that Whistler waves may also contribute significantly to the ring current decay under appropriate conditions.
Current mode ADC design in a 0.5-μm CMOS process
Institute of Scientific and Technical Information of China (English)
Sun Yong; Lai Fengchang; Ye Yizheng
2009-01-01
This paper presents a pipelined current mode analog to digital converter (ADC) designed in a 0.5-μm CMOS process. Adopting the global and local bias scheme, the number of interconnect signal lines is reduced numerously, and the ADC exhibits the advantages of scalability and portability. Without using linear capacitance,this ADC can be implemented in a standard digital CMOS process; thus, it is suitable for applications in the system on one chip (SoC) design as an analogue IP. Simulations show that the proposed current mode ADC can operate in a wide supply range from 3 to 7 V and a wide quantization range from ±64 to ±256μA. Adopting the histogram testing method, the ADC was tested in a 3.3 V supply voltage/±64μA quantization range and a 5 V supply voltage/±256μA quantization range, respectively. The results reveal that this ADC achieves a spurious free dynamic range of 61.46dB, DNL/INL are -0.005 to +0.027 LSB/-0.1 to +0.2 LSB, respectively, under a 5 V supply voltage with a digital error correction technique.
CMOS current-mode neural associative memory design with on-chip learning.
Wu, C Y; Lan, J F
1996-01-01
Based on the Grossberg mathematical model called the outstar, a modular neural net with on-chip learning and memory is designed and analyzed. The outstar is the minimal anatomy that can interpret the classical conditioning or associative memory. It can also be served as a general-purpose pattern learning device. To realize the outstar, CMOS (complimentary metal-oxide semiconductor) current-mode analog dividers are developed to implement the special memory called the ratio-type memory. Furthermore, a CMOS current-mode analog multiplier is used to implement the correlation. The implemented CMOS outstar can on-chip store the relative ratio values of the trained weights for a long time. It can also be modularized to construct general neural nets. HSPICE (a circuit simulator of Meta Software, Inc.) simulation results of the CMOS outstar circuits as associative memory and pattern learner have successfully verified their functions. The measured results of the fabricated CMOS outstar circuits have also successfully confirmed the ratio memory and on-chip learning capability of the circuits. Furthermore, it has been shown that the storage time of the ratio memory can be as long as five minutes without refreshment. Also the outstar can enhance the contrast of the stored pattern within a long period. This makes the outstar circuits quite feasible in many applications.
Institute of Scientific and Technical Information of China (English)
PAN Xiaodong; WEI Guanghui; FAN Lisi; LU Xinfu; YANG Zhe
2013-01-01
There are the application scope limits for single differential-mode current injection test method,so in order to carry out injection susceptibility test for two-pieces equipment interconnected with both ends of a cable simultaneously,a double differential-mode current injection test method (DDMCI) is proposed.The method adopted the equivalence source wave theorem and Baum-Liu-Tesche (BLT)equation as its theory foundation.The equivalent corresponding relation between injection voltage and radiation electric field intensity is derived,and the phase relation between the two injection voltage sources is confirrned.The results indicate that the amplitude and phase of the equivalent injection voltage source is closely related to the S parameter of directional coupling device,the transmission line length,and the source vector in BLT equation,but has nothing to do with the reflection coefficient between the two equipment pieces.Therefore,by choosing the right amplitude and phase of the double injection voltage sources,the DDMCI test is equivalent to the radiation test for two interconnected equipment of a system.
Requirements on localized current drive for the suppression of neoclassical tearing modes
Bertelli, N.; De Lazzari, D.; Westerhof, E.
2011-10-01
A heuristic criterion for the full suppression of an NTM was formulated as ηNTM ≡ jCD,max/jBS >= 1.2 (Zohm et al 2005 J. Phys. Conf. Ser. 25 234), where jCD,max is the maximum in the driven current density profile applied to stabilize the mode and jBS is the local bootstrap current density. In this work we subject this criterion to a systematic theoretical analysis on the basis of the generalized Rutherford equation. Taking into account only the effect of jCD inside the island, a new criterion for full suppression by a minimum applied total current is obtained in the form of a maximum allowed value for the width of the driven current, wdep, combined with a required minimum for the total driven current in the form of wdepηNTM, where both limits depend on the marginal and saturated island sizes. These requirements can be relaxed when additional effects are taken into account, such as a change in the stability parameter Δ' from the current driven outside the island, power modulation, the accompanying heating inside the island or when the current drive is applied preemptively. When applied to ITER scenario 2, the requirement for full suppression of either the 3/2 or 2/1 NTM becomes wdep ~ 5 cm in agreement with (Sauter et al 2010 Plasma Phys. Control. Fusion 52 025002). Optimization of the ITER ECRH Upper Port Launcher design towards minimum required power for full NTM suppression requires an increase in the toroidal injection angle of the lower steering mirror of several degrees compared with its present design value, while for the upper steering mirror the present design value is close to the optimum.
Organising medication discontinuation
DEFF Research Database (Denmark)
Nixon, Michael; Kousgaard, Marius Brostrøm
2016-01-01
Background: Discontinuing medications is a complex decision making process and an important medical practice. It is a tool in reducing polypharmacy, reducing health system expenditure and improving patient quality of life. Few studies have looked at how general practitioners (GPs) discontinue...... a medication, in agreement with the patients, from a professional perspective. Three research questions were examined in this study: when does medication discontinuation occur in general practice, how is discontinuing medication handled in the GP’s practice and how do GPs make decisions about discontinuing...... medication? Methods: Twenty four GPs were interviewed using a maximum variation sample strategy. Participant observations were done in three general practices, for one day each, totalling approximately 30 consultations. Results: The results show that different discontinuation cues (related to the type...
A Novel Current-Mode Differential Transconductance LNA for IEEE 802.11a Application
Tu, Yuxiang; Wang, Chunhua; Chen, Lei; Wu, Zhangbin; Zhang, Guangxiang
2012-03-01
In this paper, a novel current-mode differential transconductance low noise amplifier (LNA) designed in the chartered 0.18 μm CMOS technology is proposed to realize the receiver front-end. The proposed LNA frequency ranges from 4.7 GHz to 6 GHz,mainly targeting at IEEE802.11a application. It utilizes two stage structure, with a PMOS current-mirrorr using inductive series peaking technique to achieve optimized current output. The noise performance is improved through the use of a gm-boosting technique, while the gain performance is improved and power consumption is saved by using current-reused technique. Measured results demonstrate that the circuit provides flat transconductance gain higher than 17.0 dB, noise figure lower than 2.31 dB and low operating voltage of 0.85 V in frequency band. A comparison with other LNAs in similar and nearby frequency bands shows the proposed LNA has advantages of higher gain, lower noise figure and better other performances.
Kink-like mode of a double gradient instability in a compressible plasma current sheet
Korovinskiy, D.B.; Ivanova, V.V.; Erkaev, N.V.; Semenov, V.S.; Ivanov, I.B.; Biernat, H.K.; Zellinger, M.
2011-01-01
A linear MHD instability of the electric current sheet, characterized by a small normal magnetic field component, varying along the sheet, is investigated. The tangential magnetic field component is modeled by a hyperbolic function, describing Harris-like variations of the field across the sheet. For this problem, which is formulated in a 3D domain, the conventional compressible ideal MHD equations are applied. By assuming Fourier harmonics along the electric current, the linearized 3D equations are reduced to 2D ones. A finite difference numerical scheme is applied to examine the time evolution of small initial perturbations of the plasma parameters. This work is an extended numerical study of the so called “double gradient instability”, – a possible candidate for the explanation of flapping oscillations in the magnetotail current sheet, which has been analyzed previously in the framework of a simplified analytical approach for an incompressible plasma. The dispersion curve is obtained for the kink-like mode of the instability. It is shown that this curve demonstrates a quantitative agreement with the previous analytical result. The development of the instability is investigated also for various enhanced values of the normal magnetic field component. It is found that the characteristic values of the growth rate of the instability shows a linear dependence on the square root of the parameter, which scales uniformly the normal component of the magnetic field in the current sheet. PMID:22053125
Bae, Woorham; Yoon, Kyung Jean; Hwang, Cheol Seong; Jeong, Deog-Kyoon
2016-12-02
This paper describes a novel readout scheme that enables the complete cancellation of sneak currents in resistive switching random-access memory (RRAM) crossbar array. The current-mode readout is employed in the proposed readout, and a few critical advantages of the current-mode readout for crossbar RRAM are elucidated in this paper. The proposed scheme is based on a floating readout scheme for low power consumption, and one more sensing port is introduced using an additional reference word line. From the additional port, information on the sneak current amount is collected, and simple current-mode arithmetic operations are implemented to cancel out the sneak current from the sensing current. In addition, a simple method of handling the overestimated-sneak-current issue is described. The proposed scheme is verified using HSPICE simulation. Moreover, an example of a current-mode sense amplifier realizing the proposed cancelling technique is presented. The proposed sense amplifier can be implemented with less hardware overhead compared to the previous works.
Bae, Woorham; Yoon, Kyung Jean; Hwang, Cheol Seong; Jeong, Deog-Kyoon
2016-12-01
This paper describes a novel readout scheme that enables the complete cancellation of sneak currents in resistive switching random-access memory (RRAM) crossbar array. The current-mode readout is employed in the proposed readout, and a few critical advantages of the current-mode readout for crossbar RRAM are elucidated in this paper. The proposed scheme is based on a floating readout scheme for low power consumption, and one more sensing port is introduced using an additional reference word line. From the additional port, information on the sneak current amount is collected, and simple current-mode arithmetic operations are implemented to cancel out the sneak current from the sensing current. In addition, a simple method of handling the overestimated-sneak-current issue is described. The proposed scheme is verified using HSPICE simulation. Moreover, an example of a current-mode sense amplifier realizing the proposed cancelling technique is presented. The proposed sense amplifier can be implemented with less hardware overhead compared to the previous works.
Current-mode implementation of processing modules in ART-based neural networks
Lopez-Alcantud, Jose-Alejandro; Hauer, Hans; Diaz-Madrid, Jose-Angel; Ruiz-Merino, Ramon
2003-04-01
This paper describes implementation of neural network processing layers using basic current-mode operating modules. The research work has been focused on the implementation of neural networks based on the Adaptive Resonance Theory, developed by S. Grossberg and G.A. Carpenter. The ART-based neural network whose operating modules have been choosen for development is the one called MART, proposed by F. Delgado, because of its complex architecture, auto--adaptive self-learning process, able to discard unmeaningful cathegories. Our presentation starts introducing the behaviour of MART with an analysis of its structure. The development described by this research work is focused on the monochannel block included in the main signal processing part of the MART neural network. The description of the computing algorithm of the layers inside a monochannel block are also provided in order to show what operational current-mode modules are needed (multiplier, divider, square-rooter, adder, substractor, absolute value, maximum and minimum evaluator...). Descriptions at schematic and layout levels of all the processing layers are given. All of them have been designed using AMS 0.35 micron technology with a supply voltage of 3.3 volts. The modules are designed to deal with input currents in the range of 20 to 50 microamps, showing a lineal behaviour and an output error of less than 10%, which is good enough for neural signal processing systems. The maximum frecuency of operation is around 200 kHz. Simulation results are included to show that the operation performed by the hardware designed matches the behaviour described by the MART neural network. For testing purposes we show the design of a monochannel block hardware implementation restricted to five inputs and three cathegories.
A Failure Mode in Dense Infrared Detector Arrays Resulting in Increased Dark Current
Pinkie, Benjamin; Bellotti, Enrico
2016-09-01
In this paper, we investigate a failure mode that arises in dense infrared focal plane detector arrays as a consequence of the interactions of neighboring pixels through the minority carrier profiles in the common absorber layer. We consider the situation in which one pixel in a hexagonal array becomes de-biased relative to its neighbors and show that the dark current in the six neighboring pixels increases exponentially as a function of the difference between the nominal and anomalous biases. Moreover, we show that the current increase in the six nearest-neighbor pixels is in total larger than that by which the current in the affected pixel decreases, causing a net increase in the dark current. The physical origins of this effect are explained as being due to increased lateral diffusion currents that arise as a consequence of breaking the symmetry of the minority carrier profiles. We then perform a parametric study to quantify the magnitude of this effect for a number of detector geometric parameters, operating temperatures, and spectral bands. Particularly, numerical simulations are carried out for short-, mid-, and long-wavelength HgCdTe infrared detectors operating between 77 K and 210 K. We show that this effect is most prevalent in architectures for which the lateral diffusion current is the largest component of the total dark current—high operating temperature devices with narrow epitaxial absorber thicknesses and pitches small compared to the diffusion length of minority carriers. These results could prove significant particularly for short- and mid-wave infrared detectors, which are typically designed to fit these conditions.
High-Precision Multi-Wave Rectifier Circuit Operating in Low Voltage + 1.5 Volt Current Mode
Directory of Open Access Journals (Sweden)
Bancha Burapattanasiri
2009-12-01
Full Text Available This article is present high-precision multi-wave rectifier circuit operating in low voltage +/- 1.5 Volt current modes by CMOS technology 0.5 μm, receive input and give output in current mode, respond at high frequency period. The structure compound with high-speed current comparator circuit, current mirror circuit, and CMOS inverter circuit. PSpice program used for confirmation the performance of testing. The PSpice program shows operating of circuit is able to working at maximum input current 400 μAp-p, maximum frequency responding 200 MHz, high precision and low power losses, and non-precision zero crossing output signal.Keywords-component; rectifier circuit; high-precision; low voltage; current mode;
Petit, Jean; van der Werf, Hayo M G
2003-08-01
The current industrial pig production model is in crisis, due to its association with environmental pollution, doubtful product quality and lack of animal well-being. In Bretagne (France), a region of intensive pig production, a survey of seven stakeholder groups concerned with pig production was conducted, as part of a research programme dedicated to the assessment of the environmental impact of different modes of pig production. A very large majority of pig producers (93%) and their suppliers (100%) considers pig farms as an asset for the region, whereas a majority of scientists (58%), activists (78%) and consumers (54%) sees it as a handicap. Differences among stakeholder groups are minor with respect to the perceived importance of environmental and social issues. Stakeholders agree on the relative level of responsibility of pig farms with respect to specific problems. For all groups unpleasant odours and water quality come first with respect to responsibility, for most groups soil quality comes second, followed by product safety and air quality. For a future improved mode of pig production, 76% of pig producers and their suppliers prefer to adapt the current model, for all other groups the majority prefers an alternative model. While pig producers and their suppliers prefer a slurry-based housing system, all other groups prefer a straw-based system. Pig producers see the slurry-based system as technically superior and associate the straw-based system with poor working conditions, whereas consumers associate the slurry-based system in the first place with poor water quality and associate the straw-based system with less pollution. These results will be of use in the research programme on the environmental impact of modes of pig production, as they indicate the environmental impacts to be considered and their relative importance. The results will also help in deciding which options should be assessed. It is concluded that the poor image of the current pig
Hakim, Issa; Laquai, Rene; Walter, David; Mueller, Bernd; Graja, Paul; Meyendorf, Norbert; Donaldson, Steven
2017-02-01
Carbon fiber composites have been increasingly used in aerospace, military, sports, automotive and other fields due to their excellent properties, including high specific strength, high specific modulus, corrosion resistance, fatigue resistance, and low thermal expansion coefficient. Interlaminar fracture is a serious failure mode leading to a loss in composite stiffness and strength. Discontinuities formed during manufacturing process degrade the fatigue life and interlaminar fracture resistance of the composite. In his study, three approaches were implemented and their results were correlated to quantify discontinuities effecting static and fatigue interlaminar fracture behavior of carbon fiber composites. Samples were fabricated by hand layup vacuum bagging manufacturing process under three different vacuum levels, indicated High (-686 mmHg), Moderate (-330 mmHg) and Poor (0 mmHg). Discontinuity content was quantified through-thickness by destructive and nondestructive techniques. Eight different NDE methods were conducted including imaging NDE methods: X-Ray laminography, ultrasonic, high frequency eddy current, pulse thermography, pulse phase thermography and lock-in-thermography, and averaging NDE techniques: X-Ray refraction and thermal conductivity measurements. Samples were subsequently destructively serial sectioned through-thickness into several layers. Both static and fatigue interlaminar fracture behavior under Mode I were conducted. The results of several imaging NDE methods revealed the trend in percentages of discontinuity. However, the results of averaging NDE methods showed a clear correlation since they gave specific values of discontinuity through-thickness. Serial sectioning exposed the composite's internal structure and provided a very clear idea about the type, shape, size, distribution and location of most discontinuities included. The results of mechanical testing showed that discontinuities lead to a decrease in Mode I static interlaminar
A two-fluid study of oblique tearing modes in a force-free current sheet
Energy Technology Data Exchange (ETDEWEB)
Akçay, Cihan, E-mail: akcay@lanl.gov; Daughton, William [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Lukin, Vyacheslav S. [National Science Foundation, Arlington, Virginia 22230 (United States); Liu, Yi-Hsin [NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)
2016-01-15
Kinetic simulations have demonstrated that three-dimensional reconnection in collisionless regimes proceeds through the formation and interaction of magnetic flux ropes, which are generated due to the growth of tearing instabilities at multiple resonance surfaces. Since kinetic simulations are intrinsically expensive, it is desirable to explore the feasibility of reduced two-fluid models to capture this complex evolution, particularly, in the strong guide field regime, where two-fluid models are better justified. With this goal in mind, this paper compares the evolution of the collisionless tearing instability in a force-free current sheet with a two-fluid model and fully kinetic simulations. Our results indicate that the most unstable modes are oblique for guide fields larger than the reconnecting field, in agreement with the kinetic results. The standard two-fluid tearing theory is extended to address the tearing instability at oblique angles. The resulting theory yields a flat oblique spectrum and underestimates the growth of oblique modes in a similar manner to kinetic theory relative to kinetic simulations.
Fast-to-Alfv\\'en Mode Conversion Mediated by Hall Current. I. Cold Plasma Model
Cally, Paul S
2015-01-01
The photospheric temperature minimum in the Sun and solar-like stars is very weakly ionized, with ionization fraction $f$ as low as $10^{-4}$. In galactic star forming regions, $f$ can be $10^{-10}$ or lower. Under these circumstances, the Hall current can couple low frequency Alfv\\'en and magneto\\-acoustic waves via the dimensionless Hall parameter $\\epsilon=\\omega/\\Omega_\\text{i}f$, where $\\omega$ is the wave frequency and $\\Omega_\\text{i}$ is the mean ion gyrofrequency. This is analysed in the context of a cold (zero-$\\beta$) plasma, and in less detail for a warm plasma. It is found that Hall coupling preferentially occurs where the wave vector is nearly field-aligned. In these circumstances, Hall coupling in theory produces a continual oscillation between fast and Alfv\\'en modes as the wave passes through the weakly ionized region. At low frequencies (mHz), characteristic of solar and stellar normal modes, $\\epsilon$ is probably too small for more than a fraction of one oscillation to occur. On the other ...
Current mode pulse width modulation/pulse position modulation based on phase lock loop
Wisartpong, Pichet; Silaphan, Vorapong; Kurutach, Sunee; Wardkein, Paramote
2017-05-01
In this paper, the fully integrated CMOS current mode PLL with current input injects at the place of input or output of the loop filter without summing amplifier circuit. It functions as PPM and PWM circuit is present. In addition, its frequency response is an analysis which electronic tuning BPF and LPF are obtained. The proposed circuit has been designed with 0.18 μm CMOS technology. The simulation results of this circuit can be operated at 2.5 V supply voltage, at center frequency 100 MHz. The linear range of input current can be adjusted from 43 μA to 109 μA, and the corresponding duty cycle of pulse width output is from 93% to 16% and the normalized pulse position is from 0.93 to 0.16. The power dissipation of this circuit is 4.68 mW with the total chip area is 28 μm × 60 μm.
Iterative current mode per pixel ADC for 3D SoftChip implementation in CMOS
Lachowicz, Stefan W.; Rassau, Alexander; Lee, Seung-Minh; Eshraghian, Kamran; Lee, Mike M.
2003-04-01
Mobile multimedia communication has rapidly become a significant area of research and development constantly challenging boundaries on a variety of technological fronts. The processing requirements for the capture, conversion, compression, decompression, enhancement, display, etc. of increasingly higher quality multimedia content places heavy demands even on current ULSI (ultra large scale integration) systems, particularly for mobile applications where area and power are primary considerations. The ADC presented in this paper is designed for a vertically integrated (3D) system comprising two distinct layers bonded together using Indium bump technology. The top layer is a CMOS imaging array containing analogue-to-digital converters, and a buffer memory. The bottom layer takes the form of a configurable array processor (CAP), a highly parallel array of soft programmable processors capable of carrying out complex processing tasks directly on data stored in the top plane. This paper presents a ADC scheme for the image capture plane. The analogue photocurrent or sampled voltage is transferred to the ADC via a column or a column/row bus. In the proposed system, an array of analogue-to-digital converters is distributed, so that a one-bit cell is associated with one sensor. The analogue-to-digital converters are algorithmic current-mode converters. Eight such cells are cascaded to form an 8-bit converter. Additionally, each photo-sensor is equipped with a current memory cell, and multiple conversions are performed with scaled values of the photocurrent for colour processing.
Zhang, Shuangxi
2014-01-01
The past studies treated the perturbed distribution of circulating electrons as adiabatic one when studying the dispersion relation of electrostatic geodesic acoustic mode(GAM). In this paper, the flow of electron geodesic current (FEGC) is added to modify this adiabatic distribution. Based on the drift kinetic theory, it is found that FEGC obviously increases the magnitude of the standard GAM's frequency and reduces its damping rate. The increase of frequency results from the contribution of FEGC to the radial flow. The reason for the reduction of damping rate is that when the effect of FEGC counts, the new resonant velocity becomes much larger than ions thermal velocity with equilibrium distribution obeying Maxwellian distribution, compared with unmodified Landau resonant velocity. Especially, FEGC changes the characters of the frequency and damping rate of low-frequency GAM as functions of safety factor $q$ .
A Two-Fluid Study of Oblique Tearing Modes in a Force-Free Current Sheet
Akcay, Cihan; Lukin, Vyacheslav S; Liu, Yi-Hsin
2016-01-01
Kinetic simulations have demonstrated that three-dimensional reconnection in collisionless regimes proceeds through the formation and interaction of magnetic flux ropes, which are generated due to the growth of tearing instabilities at multiple resonance surfaces. Since kinetic simulations are intrinsically expensive, it is desirable to explore the feasibility of reduced two-fluid models to capture this complex evolution, particularly, in the strong guide field regime, where two-fluid models are better justified. With this goal in mind, this paper compares the evolution of the collisionless tearing instability in a force-free current sheet with a two-fluid model and fully kinetic simulations. Our results indicate that the most unstable modes are oblique for guide fields larger than the reconnecting field, in agreement with the kinetic results. The standard two-fluid tearing theory is extended to address the tearing instability at oblique angles. The resulting theory yields a flat oblique spectrum and underest...
DEFF Research Database (Denmark)
Nielsen, Dennis; Knott, Arnold; Andersen, Michael A. E.
2013-01-01
A hysteretic self-oscillating bandpass current mode control (BPCM) scheme for Class D audio amplifiers driving capacitive transducers are presented. The scheme provides excellent stability margins and low distortion over a wide range of operating conditions. Small-signal behavior of the amplifier...... the rules of electrostatics have been known as very interesting alternatives to the traditional inefficient electrodynamic transducers. When driving capacitive transducers from a Class D audio amplifier the high impedance nature of the load represents a key challenge. The BPCM control scheme ensures a flat...... is analysis through transfer function based linear control methodology. Measurements are performed on a single-ended ± 300 V half-bridge amplifier driving a capacitive load of 100 nF. Total Harmonic Distortion plus noise (THD+N) below 0.1 % are reported. Transducers representing a capacitive load and obeying...
Energy Technology Data Exchange (ETDEWEB)
McClenaghan, J.; Lin, Z.; Holod, I.; Deng, W.; Wang, Z. [University of California, Irvine, California 92697 (United States)
2014-12-15
The gyrokinetic toroidal code (GTC) capability has been extended for simulating internal kink instability with kinetic effects in toroidal geometry. The global simulation domain covers the magnetic axis, which is necessary for simulating current-driven instabilities. GTC simulation in the fluid limit of the kink modes in cylindrical geometry is verified by benchmarking with a magnetohydrodynamic eigenvalue code. Gyrokinetic simulations of the kink modes in the toroidal geometry find that ion kinetic effects significantly reduce the growth rate even when the banana orbit width is much smaller than the radial width of the perturbed current layer at the mode rational surface.
Controllability of Discontinuous Systems
Veliov, V. M.; Krastanov, M.
1988-01-01
This report presents an approach to the local controllability problem for a discontinuous system. The approach is based on a concept of tangent vector field to a generalized dynamic system, which makes possible the differential geometry tools to be applied in the discontinuous case. Sufficient controllability conditions are derived.
2007-01-01
Video observation has shown that feeding-current-producing calanoid copepods modulate their feeding currents by displaying a sequence of different swimming behaviours during a time period of up to tens of seconds. In order to understand the feeding-current modulation process, we numerically modelled the steady feeding currents for different modes of observed copepod motion behaviours (i.e. free sinking, partial sinking, hovering, vertical swimming upward and horizontal swimming backward or fo...
Discontinuous spirals of stable periodic oscillations.
Sack, Achim; Freire, Joana G; Lindberg, Erik; Pöschel, Thorsten; Gallas, Jason A C
2013-11-27
We report the experimental discovery of a remarkable organization of the set of self-generated periodic oscillations in the parameter space of a nonlinear electronic circuit. When control parameters are suitably tuned, the wave pattern complexity of the periodic oscillations is found to increase orderly without bound. Such complex patterns emerge forming self-similar discontinuous phases that combine in an artful way to produce large discontinuous spirals of stability. This unanticipated discrete accumulation of stability phases was detected experimentally and numerically in a Duffing-like proxy specially designed to bypass noisy spectra conspicuously present in driven oscillators. Discontinuous spirals organize the dynamics over extended parameter intervals around a focal point. They are useful to optimize locking into desired oscillatory modes and to control complex systems. The organization of oscillations into discontinuous spirals is expected to be generic for a class of nonlinear oscillators.
Discontinuous Spirals of Stable Periodic Oscillations
Sack, Achim; Freire, Joana G.; Lindberg, Erik; Pöschel, Thorsten; Gallas, Jason A. C.
2013-01-01
We report the experimental discovery of a remarkable organization of the set of self-generated periodic oscillations in the parameter space of a nonlinear electronic circuit. When control parameters are suitably tuned, the wave pattern complexity of the periodic oscillations is found to increase orderly without bound. Such complex patterns emerge forming self-similar discontinuous phases that combine in an artful way to produce large discontinuous spirals of stability. This unanticipated discrete accumulation of stability phases was detected experimentally and numerically in a Duffing-like proxy specially designed to bypass noisy spectra conspicuously present in driven oscillators. Discontinuous spirals organize the dynamics over extended parameter intervals around a focal point. They are useful to optimize locking into desired oscillatory modes and to control complex systems. The organization of oscillations into discontinuous spirals is expected to be generic for a class of nonlinear oscillators. PMID:24284508
Single-input Multiple-output Tunable Log-domain Current-mode Universal Filter
Directory of Open Access Journals (Sweden)
P. Prommee
2013-06-01
Full Text Available This paper describes the design of a current-mode single-input multiple-output (SIMO universal filter based on the log-domain filtering concept. The circuit is a direct realization of a first-order differential equation for obtaining the lossy integrator circuit. Lossless integrators are realized by log-domain lossy integrators. The proposed filter comprises only two grounded capacitors and twenty-four transistors. This filter suits to operate in very high frequency (VHF applications. The pole-frequency of the proposed filter can be controlled over five decade frequency range through bias currents. The pole-Q can be independently controlled with the pole-frequency. Non-ideal effects on the filter are studied in detail. A validated BJT model is used in the simulations operated by a single power supply, as low as 2.5 V. The simulation results using PSpice are included to confirm the good performances and are in agreement with the theory.
Superpersistent currents and whispering gallery modes in relativistic quantum chaotic systems.
Xu, Hongya; Huang, Liang; Lai, Ying-Cheng; Grebogi, Celso
2015-03-11
Persistent currents (PCs), one of the most intriguing manifestations of the Aharonov-Bohm (AB) effect, are known to vanish for Schrödinger particles in the presence of random scatterings, e.g., due to classical chaos. But would this still be the case for Dirac fermions? Addressing this question is of significant value due to the tremendous recent interest in two-dimensional Dirac materials. We investigate relativistic quantum AB rings threaded by a magnetic flux and find that PCs are extremely robust. Even for highly asymmetric rings that host fully developed classical chaos, the amplitudes of PCs are of the same order of magnitude as those for integrable rings, henceforth the term superpersistent currents (SPCs). A striking finding is that the SPCs can be attributed to a robust type of relativistic quantum states, i.e., Dirac whispering gallery modes (WGMs) that carry large angular momenta and travel along the boundaries. We propose an experimental scheme using topological insulators to observe and characterize Dirac WGMs and SPCs, and speculate that these features can potentially be the base for a new class of relativistic qubit systems. Our discovery of WGMs in relativistic quantum systems is remarkable because, although WGMs are common in photonic systems, they are relatively rare in electronic systems.
Novel Resistorless First-Order Current-Mode Universal Filter Employing a Grounded Capacitor
Directory of Open Access Journals (Sweden)
R. Arslanalp
2011-09-01
Full Text Available In this paper, a new bipolar junction transistor (BJT based configuration for providing first-order resistorless current-mode (CM all-pass, low-pass and high-pass filter responses from the same configuration is suggested. The proposed circuit called as a first-order universal filter possesses some important advantages such as consisting of a few BJTs and a grounded capacitor, consuming very low power and having electronic tunability property of its pole frequency. Additionally, types of filter response can be obtained only by changing the values of current sources. The suggested circuit does not suffer from disadvantages of use of the resistors in IC process. The presented first-order universal filter topology does not need any passive element matching constraints. Moreover, as an application example, a second-order band-pass filter is obtained by cascading two proposed filter structures which are operating as low-pass filter and high-pass one. Simulations by means of PSpice program are accomplished to demonstrate the performance and effectiveness of the developed first-order universal filter.
Institute of Scientific and Technical Information of China (English)
周有平; 陈国杰; 李斌
2016-01-01
提出了利用电流纹波率设计反激式变压器和判别其导通模式的方法，用该方法导出了反激式变压器从CCM进入DCM模式的数学式，用MATLAB计算并分析了输入电压、负载电流及反射电压对导通模式的影响。计算表明，最小电流纹波率或反射电压取值越大，反激变压器在输入电压增大或负载电流减小时越容易进入DCM模式。设计了一款24 V 1.5 A反激式开关稳压电源，测量了变压器的电流波形。实验表明，测量结果与推导的数学式相符，用电流纹波率设计反激式变压器比传统的波形系数更直观和便于测量。%A method to design a flyback transformer and distinguish its conduction modes is proposed based on the current ripple ratio. An equation for the flyback transformer going into the discontinuous conduction mode from the initial continuous conduction mode is derived by using this method. According to the equation,the calculation is performed by MATLAB,and the effects of the input voltage,load current or reflected secondary voltage on the con⁃duction mode of the flyback transformer are analyzed. The calculation indicates the greater the minimum current rip⁃ple ratio or reflection voltage is,the more easily the flyback transformer goes into the discontinuous conduction mode when the input voltage increases or load current decreases. Then,a 24 V 1.5 A flyback switching power sup⁃ply is designed,and the current waveforms of the flyback transformer are measured. The experiment shows that the measured results are agreement with the derived equation,and the current ripple ratio is more intuitive and easier to be measured than the current wave factor.
DEFF Research Database (Denmark)
Sørensen, Morten; Hubing, Todd H.; Jensen, Kim
2016-01-01
Common-mode current on attached cables is a typical source for radiated emission. Several models have been made for conversion of the intended differential signal to unwanted common-mode current on cables. In this paper we refine a method for identifying the radiation sources arising from a long...... microstrip. This method is used to show that the radiated emission from a PCB with attached cable(s) caused by a long trace depends on whether the trace is facing up or down with different result for voltage and current sources....
A general approach for calculating coupling impedances of small discontinuities
Kurennoy, S S; Stupakov, G V; Kurennoy, Sergey S; Gluckstern, Robert L; Stupakov, Gennady V
1995-01-01
A general theory of the beam interaction with small discontinuities of the vacuum chamber is developed taking into account the reaction of radiated waves back on the discontinuity. The reactive impedance calculated earlier is reproduced as the first order, and the resistive one as the second order of a perturbation theory based on this general approach. The theory also gives, in a very natural way, the results for the trapped modes due to small discontinuities obtained earlier by a different method.
A General approach for calculating coupling impedances of small discontinuities
Kurennoy, Sergei S.; Gluckstern, Robert L.; Stupakov, Gennady V.
A general theory of the beam interaction with small discontinuities of the vacuum chamber is developed taking into account the reaction of radiated waves back on the discontinuity. The reactive impedance calculated earlier is reproduced as the first order, and the resistive one as the second order of a perturbation theory based on this general approach. The theory also gives, in a very natural way, the results for the trapped modes due to small discontinuities obtained earlier by a different method.
Directory of Open Access Journals (Sweden)
Nittala S K Sastry
2012-06-01
Full Text Available This paper presents a new PWM Multi phase DC-DC converter under current mode control with an auxiliary circuit which provides zero voltage switching in order to meet the power supply requirements of the processors of modern electronic equipments like laptops, mobiles, and PDAs etc which require more than 70 A current, lower voltage and better transient response.The multi phase topology benefits in high current, good efficiency and better current transient response. High current multi phase buck converters found applications in advanced data control, solid state lasers, communication equipment and Pentium processors etc. In this paper designed of three phase DC-DC converter 100W, 12V/1V under current mode control is discussed in detail and the simulation results are presented to support the theoretical analysis.
Energy Technology Data Exchange (ETDEWEB)
Ardela, A.; Cooper, W.A. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)
1996-09-01
In this paper we resume a numerical study of the global stability of plasma with helical boundary deformation and non null net toroidal current. The aim was to see whether external modes with n=1,2 (n toroidal mode number) can be stabilized at values of {beta} inaccessible to the tokamak. L=2,3 configurations with several aspect ratios and different numbers of equilibrium field periods are considered. A large variety of toroidal current densities and different pressure profiles are taken into account. Mercier stability is also investigated. (author) 4 figs., 6 refs.
Firago, B. I.; K. M. Medvedev
2006-01-01
The purpose of the paper is to investigate dependence of input current harmonic spectrum of modern frequency converters with uncontrolled rectifiers on supply network power , rated power and motor load, and also the DC filter capacity. Results of the investigations are given in the form of the corresponding dependencies and an estimation of correspondence of higher current harmonic levels generated by a frequency converter to the existing state standard.
DEFF Research Database (Denmark)
Migliucci, P.; Naulin, Volker
2010-01-01
Fast magnetic pickup coils are used in forward modeling to match parameters in a simple edge localized mode (ELM) filament model. This novel method allows us to determine key parameters for the evolution of the ELM filaments, as effective mode number, radial and toroidal velocities, and average...
A CMOS power-efficient low-noise current-mode front-end amplifier for neural signal recording.
Wu, Chung-Yu; Chen, Wei-Ming; Kuo, Liang-Ting
2013-04-01
In this paper, a new current-mode front-end amplifier (CMFEA) for neural signal recording systems is proposed. In the proposed CMFEA, a current-mode preamplifier with an active feedback loop operated at very low frequency is designed as the first gain stage to bypass any dc offset current generated by the electrode-tissue interface and to achieve a low high-pass cutoff frequency below 0.5 Hz. No reset signal or ultra-large pseudo resistor is required. The current-mode preamplifier has low dc operation current to enhance low-noise performance and decrease power consumption. A programmable current gain stage is adopted to provide adjustable gain for adaptive signal scaling. A following current-mode filter is designed to adjust the low-pass cutoff frequency for different neural signals. The proposed CMFEA is designed and fabricated in 0.18-μm CMOS technology and the area of the core circuit is 0.076 mm(2). The measured high-pass cutoff frequency is as low as 0.3 Hz and the low-pass cutoff frequency is adjustable from 1 kHz to 10 kHz. The measured maximum current gain is 55.9 dB. The measured input-referred current noise density is 153 fA /√Hz , and the power consumption is 13 μW at 1-V power supply. The fabricated CMFEA has been successfully applied to the animal test for recording the seizure ECoG of Long-Evan rats.
Yamacli, Serhan; Ozcan, Sadri; Kuntman, Hakan
2011-08-01
In this paper, an active-only grounded lossless inductance simulator operating in current-mode is presented. The circuit uses only a current operational amplifier (COA) and an operational transconductance amplifier (OTA). The novelty of the proposed circuit is that it uses a COA instead of a voltage operational amplifier (VOA) to take the wider frequency operation advantage of the current-mode approach. The simulation results obtained through SPICE with 0.5 μm standard CMOS technology verify that the designed circuit can be operated up to 30 MHz, which is much higher than the operation frequency of previously reported inductance simulators utilising VOAs. The inductance value of the presented circuit can be adjusted electronically between 3.9 μH and 37 μH via the biasing current of the OTA. A parallel resonance circuit application is also given validating the operation of the proposed inductance simulator.
A Dual-Mode Step-up DC/DC Converter IC with Current-Limiting and EMI Reduction Techniques
Institute of Scientific and Technical Information of China (English)
Wan-Rone Liou; Chun-Ting Kuo; Mei-Ling Yeh; Ping-Hsing Chen; Marynelle L. Z. Rosales
2008-01-01
This paper presents a novel dual-mode step-up (boost) DC/DC converter. Pulse-frequency modulation (PFM) is used to improve the efficiency at light load. This converter can operate between pulse-width modulation (PWM) and pulse-frequency modulation. The converter will operate in PFM mode at light load and in PWM mode at heavy load. The maximum conversion efficiency of this converter is 96%. The conversion efficiency is greatly improved when load current is below 100 mA. Additionally, a soft-start circuit and a variable-sawtooth frequency circuit are proposed in this paper. The former is used to avoid the large switching current at the start up of the converter and the latter is utilized to reduce the EMI of the converter.
Gilliland, M. G.; Rougelot, R. S.; Schumaker, R. A.
1966-01-01
Video signal processor uses special-purpose integrated circuits with nonsaturating current mode switching to accept texture and color information from a digital computer in a visual spaceflight simulator and to combine these, for display on color CRT with analog information concerning fading.
Direct observation of current in type-I edge-localized-mode filaments on the ASDEX upgrade tokamak
DEFF Research Database (Denmark)
Vianello, N.; Zuin, M.; Cavazzana, R.;
2011-01-01
Magnetically confined plasmas in the high confinement regime are regularly subjected to relaxation oscillations, termed edge localized modes (ELMs), leading to large transport events. Present ELM theories rely on a combined effect of edge current and the edge pressure gradients which result in in...
Jeong, Il-Hun; Kwon, Oh-Kyong
2008-03-01
In this paper, we describe two types of 8-bit current-mode driver ICs with a small area and good performance for applications high accuracy current-mode digital-to-analog converters (DACs), and improved channel-to-channel uniformity for active matrix organic light-emitting diode (AMOLED) displays. One uses the proposed current steering DAC (type A), which is an improved architecture of a binary-weighted DAC, and the other uses a DAC that is a combination of a thermometer-decoded of the DAC and a binary-weighted type. The measured results show that the peak integral nonlinearity (INL) is within ±0.5 the least significant bit (LSB), the peak differential nonlinearity (DNL) is within ±0.5 LSB, and the nonuniformity of output current among channels and chips is within ±0.5 LSB. The size of the driver IC is 15,820 ×1,500 µm2 and the total power consumption of the current-mode driver IC is less than 9 mW when the display has full-white pattern with a luminance of 150 cd/m2. The chip area and power consumption with the proposed current DAC are reduced by 26 and 10%, respectively, compared with those of conventional driver ICs with a fully binary-weighted DAC.
La Haye, R. J.
2015-12-01
ITER is an international project to design and build an experimental fusion reactor based on the "tokamak" concept. ITER relies upon localized electron cyclotron current drive (ECCD) at the rational safety factor q=2 to suppress or stabilize the expected poloidal mode m=2, toroidal mode n=1 neoclassical tearing mode (NTM) islands. Such islands if unmitigated degrade energy confinement, lock to the resistive wall (stop rotating), cause loss of "H-mode" and induce disruption. The International Tokamak Physics Activity (ITPA) on MHD, Disruptions and Magnetic Control joint experiment group MDC-8 on Current Drive Prevention/Stabilization of Neoclassical Tearing Modes started in 2005, after which assessments were made for the requirements for ECCD needed in ITER, particularly that of rf power and alignment on q=2 [1]. Narrow well-aligned rf current parallel to and of order of one percent of the total plasma current is needed to replace the "missing" current in the island O-points and heal or preempt (avoid destabilization by applying ECCD on q=2 in absence of the mode) the island [2-4]. This paper updates the advances in ECCD stabilization on NTMs learned in DIII-D experiments and modeling during the last 5 to 10 years as applies to stabilization by localized ECCD of tearing modes in ITER. This includes the ECCD (inside the q=1 radius) stabilization of the NTM "seeding" instability known as sawteeth (m/n=1/1) [5]. Recent measurements in DIII-D show that the ITER-similar current profile is classically unstable, curvature stabilization must not be neglected, and the small island width stabilization effect from helical ion polarization currents is stronger than was previously thought [6]. The consequences of updated assumptions in ITER modeling of the minimum well-aligned ECCD power needed are all-in-all favorable (and well-within the ITER 24 gyrotron capability) when all effects are included. However, a "wild card" may be broadening of the localized ECCD by the presence of
Discontinuous Spirals of Stable Periodic Oscillations
DEFF Research Database (Denmark)
Sack, Achim; Freire, Joana G.; Lindberg, Erik
2013-01-01
We report the experimental discovery of a remarkable organization of the set of self-generated periodic oscillations in the parameter space of a nonlinear electronic circuit. When control parameters are suitably tuned, the wave pattern complexity of the periodic oscillations is found to increase...... orderly without bound. Such complex patterns emerge forming self-similar discontinuous phases that combine in an artful way to produce large discontinuous spirals of stability. This unanticipated discrete accumulation of stability phases was detected experimentally and numerically in a Duffing-like proxy...... specially designed to bypass noisy spectra conspicuously present in driven oscillators. Discontinuous spirals organize the dynamics over extended parameter intervals around a focal point. They are useful to optimize locking into desired oscillatory modes and to control complex systems. The organization...
Current modes of failure in TKA: infection, instability, and stiffness predominate.
Le, David H; Goodman, Stuart B; Maloney, William J; Huddleston, James I
2014-07-01
Historically, polyethylene wear and its sequelae (osteolysis, late instability, aseptic loosening) were common causes for revision total knee arthroplasty (TKA). Recently, polyethylene manufacturing has become more consistent; furthermore, a clearer understanding of the importance of oxidation on polyethylene performance led to packaging of the polyethylene bearings in an inert environment. This improved the quality and consistency of polyethylene used in TKA, raising the question of whether different failure modes now predominate after TKA. The purpose of this study was to determine the current reasons for (1) early and (2) late failures after TKA at one high-volume arthroplasty center. We reviewed all first-time revision TKAs performed between 2001 and 2011 at one institution, yielding a group of 253 revision TKAs in 251 patients. Mean age at the time of revision was 64 years (SD 10 years). Mean time to revision was 35 months (SD 23 months). Preoperative evaluations, laboratory data, radiographs, and intraoperative findings were used to determine causes for revision. Early failure was defined as revision within 2 years of the index procedure. The primary failure mechanism was determined by the operating surgeon. Early failure accounted for 46% (116 of 253) of all revisions with infection (28 of 116 [24%]), instability (30 of 116 [26%]), and stiffness (21 of 116 [18%]) being the leading causes. Late failure accounted for 54% (137 of 253) of all revisions with the most common causes including infection (34 of 137 [25%]), instability (24 of 137 [18%]), and stiffness (19 of 253 [14%]). Polyethylene wear was implicated as the failure mechanism in 2% of early cases (two of 116) and 9% of late cases (13 of 137). In contrast to previous studies, wear-related implant failure in TKA was relatively uncommon in this series. Changes in polyethylene manufacturing, sterilization, and storage may have accounted for some of this difference; however, longer-term followup will
Bifurcation and chaos in multi-parallel-connected current-mode controlled boost DC-DC converters
Institute of Scientific and Technical Information of China (English)
CHEN Ming-liang; MA Wei-ming
2006-01-01
This paper studied the bifurcation and chaos phenomenon in a multi-parallel-connected current-mode controlled boost DC-DC converter system with the use of nonlinear mapping bifurcation theory of two dimensions,and the changing rules of the bifurcation charts with the increase of the control parallels and control parameters were concluded.The method of discrete mapping modeling was utilized to construct the difference equations of the system operating in continuous conduction mode (CCM).Analyses and computer emulations were made.
Pratelli, Aldo
2016-01-01
This book presents a series of lectures on three of the best known examples of free discontinuity problems: the Mumford-Shah model for image segmentation, a variational model for the epitaxial growth of thin films, and the sharp interface limit of the Ohta-Kawasaki model for pattern formation in dyblock copolymers.
Energy Technology Data Exchange (ETDEWEB)
La Haye, R. J., E-mail: lahaye@fusion.gat.com [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
2015-12-10
ITER is an international project to design and build an experimental fusion reactor based on the “tokamak” concept. ITER relies upon localized electron cyclotron current drive (ECCD) at the rational safety factor q=2 to suppress or stabilize the expected poloidal mode m=2, toroidal mode n=1 neoclassical tearing mode (NTM) islands. Such islands if unmitigated degrade energy confinement, lock to the resistive wall (stop rotating), cause loss of “H-mode” and induce disruption. The International Tokamak Physics Activity (ITPA) on MHD, Disruptions and Magnetic Control joint experiment group MDC-8 on Current Drive Prevention/Stabilization of Neoclassical Tearing Modes started in 2005, after which assessments were made for the requirements for ECCD needed in ITER, particularly that of rf power and alignment on q=2 [1]. Narrow well-aligned rf current parallel to and of order of one percent of the total plasma current is needed to replace the “missing” current in the island O-points and heal or preempt (avoid destabilization by applying ECCD on q=2 in absence of the mode) the island [2-4]. This paper updates the advances in ECCD stabilization on NTMs learned in DIII-D experiments and modeling during the last 5 to 10 years as applies to stabilization by localized ECCD of tearing modes in ITER. This includes the ECCD (inside the q=1 radius) stabilization of the NTM “seeding” instability known as sawteeth (m/n=1/1) [5]. Recent measurements in DIII-D show that the ITER-similar current profile is classically unstable, curvature stabilization must not be neglected, and the small island width stabilization effect from helical ion polarization currents is stronger than was previously thought [6]. The consequences of updated assumptions in ITER modeling of the minimum well-aligned ECCD power needed are all-in-all favorable (and well-within the ITER 24 gyrotron capability) when all effects are included. However, a “wild card” may be broadening of the localized
Cuneo, M. E.; Sinars, D. B.; Bliss, D. E.; Waisman, E. M.; Porter, J. L.; Stygar, W. A.; Lebedev, S. V.; Chittenden, J. P.; Sarkisov, G. S.; Afeyan, B. B.
2005-06-01
Nested tungsten wire arrays (20-mm on 12-mm diam.) are shown for the first time to operate in a current-transfer mode at 16 19 MA, even for azimuthal interwire gaps of 0.2 mm that are the smallest typically used for any array experiment. After current transfer, the inner wire array shows discrete wire ablation and implosion characteristics identical to that of a single array, such as axially nonuniform ablation, delayed acceleration, and trailing mass and current. The presence of trailing mass from the outer and the inner arrays may play a role in determining nested array performance.
Muhammad Taher Abuelma'atti; Azhar Quddus
1996-01-01
A new voltage-mode active-filter with single input and three outputs is presented. The parameters of the proposed filter are programmable and the filter uses grounded capacitors. The proposed circuit can simultaneously realize lowpass, highpass, and bandpass biquadratic filter functions and enjoys low temperature sensitivities.
Two current experimental problems in heavy lepton physics: tau decay modes and close mass pairs
Energy Technology Data Exchange (ETDEWEB)
Perl, M.L.
1987-08-01
This paper investigates tau lepton decay modes and close-mass lepton pairs. The major part of the paper discusses branching functions from experimental and theoretical viewpoints. Finally, the lack of experimental signatures of close-mass lepton pairs are reviewed. 15 refs., 2 figs., 11 tabs. (JDH)
A Novel Electronically Controllable of Current-mode Level Shifted Multicarrier PWM Based on MO-CFTA
Directory of Open Access Journals (Sweden)
W. Kongnun
2013-09-01
Full Text Available This paper proposes the application of an electronically controlled current-mode for a level shifted multicarrier PWM generator. The proposed circuit consists of two multiple-output current follower transconductance amplifiers (MO-CFTAs for the multiple-output triangular generator and four current follower transconductance amplifiers (CFTAs for the signal comparator. The characteristics of the circuit are as follows: the current output can be controlled by bias current, the maximum amplitude deviation due to temperature variation is less than 1.37% and the power consumption is approximately 0.744 microwatt, at ±1.5V supply voltages. The proposed PWM has been verified through PSpice simulation results which are in consistent with the theoretical analysis.
Zhongjie, Guo; Longsheng, Wu; Youbao, Liu
2010-12-01
To improve the compensation for the inherent instability in a current mode converter, the adaptive slope compensation, giving attention to the problems of the traditional compensation on compensation accuracy, loading capability and turning jitter, is presented. Based on the analysis of current loop, by detecting the input and output voltage, converting the adaptive slope compensation current, the compensation of the current loop is optimized successfully. It can not only improve the compensation accuracy but also eliminate the over compensation, the turning jitter and the poor loading capability in the reported slope compensation. A power supply chip with adaptive slope compensation has been fabricated in a 0.35 μm CMOS process. The measurement results show that the chip starts up and operates steadily with the constant current limit under conditions of 5 V input voltage, from 10% to 100% duty cycle.
Chen, Hua-Pin
2014-01-01
This paper presents a versatile tunable current-mode universal biquadratic filter with four-input and three-output employing only two multioutput differential voltage current conveyors (MO-DVCCs), two grounded capacitors, and a well-known method for replacement of three grounded resistors by MOSFET-based electronic resistors. The proposed configuration exhibits high-output impedance which is important for easy cascading in the current-mode operations. The proposed circuit can be used as either a two-input three-output circuit or a three-input single-output circuit. In the operation of two-input three-output circuit, the bandpass, highpass, and bandreject filtering responses can be realized simultaneously while the allpass filtering response can be easily obtained by connecting appropriated output current directly without using additional stages. In the operation of three-input single-output circuit, all five generic filtering functions can be easily realized by selecting different three-input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency, and no inverting-type input current signals are imposed. All the passive and active sensitivities are low. Postlayout simulations were carried out to verify the functionality of the design.
Directory of Open Access Journals (Sweden)
Hua-Pin Chen
2014-01-01
Full Text Available This paper presents a versatile tunable current-mode universal biquadratic filter with four-input and three-output employing only two multioutput differential voltage current conveyors (MO-DVCCs, two grounded capacitors, and a well-known method for replacement of three grounded resistors by MOSFET-based electronic resistors. The proposed configuration exhibits high-output impedance which is important for easy cascading in the current-mode operations. The proposed circuit can be used as either a two-input three-output circuit or a three-input single-output circuit. In the operation of two-input three-output circuit, the bandpass, highpass, and bandreject filtering responses can be realized simultaneously while the allpass filtering response can be easily obtained by connecting appropriated output current directly without using additional stages. In the operation of three-input single-output circuit, all five generic filtering functions can be easily realized by selecting different three-input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency, and no inverting-type input current signals are imposed. All the passive and active sensitivities are low. Postlayout simulations were carried out to verify the functionality of the design.
Directory of Open Access Journals (Sweden)
Jiang Deng
2014-03-01
Full Text Available A spin coated LaB6 discontinuous film is covered on MgO protective layer to improve the discharge performance of alternating current plasma display panels. Under the premise of high transmittance of more than 90%, a very small amount of polycrystal LaB6 powders added in an organic solvent are chosen as the coating solution. The discharge characteristics results show that with 250 torr 5% Xe-Ne pressure, the firing voltage and discharge delay time of the test panel with LaB6/MgO double protective layer are decreased by 13.4% and 36.5%, respectively, compared with that of conventional MgO protective layer, likely owing to the low work function of LaB6. Furthermore, the aging time of the proposed structure is comparable to that of pure MgO protective layer. Therefore, it will not increase the production costs and is highly suitable to be applied for alternating current plasma display panels with low electrical power consumption.
Energy Technology Data Exchange (ETDEWEB)
Deng, Jiang, E-mail: dj78291@163.com [School of Physical Electronic, University of Electronic Science and Technology of China, No.4, Section 2, Jianshe North Road, 610054 Chengdu (China); Zeng, Baoqing [School of Physical Electronic, University of Electronic Science and Technology of China, No.4, Section 2, Jianshe North Road, 610054 Chengdu (China); Zhongshan Institute, University of Electronic Science and Technology of China, 528402 zhongshan (China); Wang, Xiaoju; Lin, Zulun; Qi, Kangcheng; Cao, Guichuan [School of Opto-electronic Information, University of Electronic Science and Technology of China, No.4, Section 2, Jianshe North Road, 610054 Chengdu (China)
2014-03-15
A spin coated LaB{sub 6} discontinuous film is covered on MgO protective layer to improve the discharge performance of alternating current plasma display panels. Under the premise of high transmittance of more than 90%, a very small amount of polycrystal LaB{sub 6} powders added in an organic solvent are chosen as the coating solution. The discharge characteristics results show that with 250 torr 5% Xe-Ne pressure, the firing voltage and discharge delay time of the test panel with LaB{sub 6}/MgO double protective layer are decreased by 13.4% and 36.5%, respectively, compared with that of conventional MgO protective layer, likely owing to the low work function of LaB{sub 6.} Furthermore, the aging time of the proposed structure is comparable to that of pure MgO protective layer. Therefore, it will not increase the production costs and is highly suitable to be applied for alternating current plasma display panels with low electrical power consumption.
Directory of Open Access Journals (Sweden)
C. Ho
2014-06-01
Full Text Available This work describes the measurement of the common-mode current conversion coefficient for a microstrip line with solid and slotted ground planes by using a VNA with a BCI probe. The radiated emissions estimated by the common-mode current conversion coefficient are further compared with those obtained by the FAC measurements. Furthermore, the proposed method was used to estimate radiated emissions from a microstrip bandpass filter. For all of the case studies, results of electromagnetic (EM simulation demonstrate the validity of the measurement results by the proposed method. Highly promising for use in EMI measurement application, the proposed method can estimate the radiated emissions by miniaturized microstrip components on a PCB when pre-tested for compliance with EMI regulations.
IS DISCONTINUOUS BERGSONISM POSSIBLE?
Directory of Open Access Journals (Sweden)
TERESA CASTELÃO-LAWLESS
2010-11-01
Full Text Available Gaston Bachelard’s position toward the philosophy of Henri Bergson is most interesting. In La Dialectique de la durée (1936, Bachelard claims that “of Bergsonism we accept everything but continuity” and that the rest of his book will be an attempt to show the possibility of a “discontinuous Bergsonism”. In this paper, I focus on the reaction of Bachelard to works of Bergson such as the Essai sur les données immédiates de la conscience (1889, L’Evolution créatrice (1907, and Durée et simultanéité: à propos de la théorie d’Einstein (1922 and demonstrate that even though the conditions necessary for the possibility of a discontinuous Bergsonism are not the same ones which Bachelard had in mind when he accepted most of Bergsonism, their phenomenologies of the scientific spirit were analogous.
Design of a current Mode Sample and Hold Circuit at sampling rate of 150 MS/s
Directory of Open Access Journals (Sweden)
Prity Yadav
2014-10-01
Full Text Available A current mode sample and hold circuit is presented in this paper at 180nm technology. The major concerns of VLSI are area, power, delay and speed. Hence, we have used a MOSFET in triode region in the proposed architecture for voltage to current conversion instead of a resistor being used in previously proposed circuit. The proposed circuit achieves high sampling frequency and with more accuracy than the previous one. The performance of the proposed circuit is depicted in the form of simulation results.
Directory of Open Access Journals (Sweden)
Guowei Cai
2014-01-01
Full Text Available As to strong nonlinearity of doubly fed induction generators (DFIG and uncertainty of its model, a novel rotor current controller with nonlinearity and robustness is proposed to enhance fault ride-though (FRT capacities of grid-connected DFIG. Firstly, the model error, external disturbances, and the uncertain factors were estimated by constructing extended state observer (ESO so as to achieve linearization model, which is compensated dynamically from nonlinear model. And then rotor current controller of DFIG is designed by using terminal sliding mode variable structure control theory (TSMC. The controller has superior dynamic performance and strong robustness. The simulation results show that the proposed control approach is effective.
System dynamics with interaction discontinuity
Luo, Albert C J
2015-01-01
This book describes system dynamics with discontinuity caused by system interactions and presents the theory of flow singularity and switchability at the boundary in discontinuous dynamical systems. Based on such a theory, the authors address dynamics and motion mechanism of engineering discontinuous systems due to interaction. Stability and bifurcations of fixed points in nonlinear discrete dynamical systems are presented, and mapping dynamics are developed for analytical predictions of periodic motions in engineering discontinuous dynamical systems. Ultimately, the book provides an alternative way to discuss the periodic and chaotic behaviors in discontinuous dynamical systems.
Institute of Scientific and Technical Information of China (English)
Wu Xiaobo; Liu Qing; Zhao Menglian; Chen Mingyang
2013-01-01
An analog implementation of a novel fixed-frequency quasi-sliding-mode controller for single-inductor dual-output (SIDO) buck converter in pseudo-continuous conduction mode (PCCM) with a self-adaptive freewheeling current level (SFCL) is presented.Both small and large signal variations around the operation point are considered to achieve better transient response so as to reduce the cross-regulation of this SIDO buck converter.Moreover,an internal integral loop is added to suppress the steady-state regulation error introduced by conventional PWM-based sliding mode controllers.Instead of keeping it as a constant value,the free-wheeling current level varies according to the load condition to maintain high power efficiency and less cross-regulation at the same time.To verify the feasibility of the proposed controller,an SIDO buck converter with two regulated output voltages,1.8 V and 3.3 V,is designed and fabricated in HEJIAN 0.35 μm CMOS process.Simulation and experiment results show that the transient time of this SIDO buck converter drops to 10 μs while the cross-regulation is reduced to 0.057 mV/mA,when its first load changes from 50 to 100 mA.
New SRCO with explicit current-mode output using two CCs and grounded capacitors
Bhaskar, D. R.; ABDALLA, Kasim K.; Senani, Raj
2011-01-01
A new Grounded-Capacitor Single Resistance Controlled Sinusoidal Oscillator (SRCO) with explicit current output using two Current Conveyors (CCs) and five passive elements is presented. The proposed circuit offers (i) independent control of condition of oscillation and frequency of oscillation, (ii) low active and passive sensitivities, (iii) use of both the grounded capacitors (suitable for IC implementation) and (iv) reasonably good frequency stability. The workability of the propo...
A Dual-Mode Step-up DC/DC Converter IC with Current-Limiting and EMI Reduction Techniques
Institute of Scientific and Technical Information of China (English)
Wan-Rone Liou; Chun-Ting Kuo; Mei-Ling Yeh; Ping-Hsing Chen; Marynelle L. Z. Rosales
2008-01-01
This paper presents a novel dual-modestep-up (boost) DC/DC converter. Pulse-frequencymodulation (PFM) is used to improve the efficiency atlight load. This converter can operate betweenpulse-width modulation (PWM) and pulse-frequencymodulation. The converter will operate in PFM mode atlight load and in PWM mode at heavy load. Themaximum conversion efficiency of this converter is 96%.The conversion efficiency is greatly improved when loadcurrent is below 100 mA. Additionally, a soft-startcircuit and a variable-sawtooth frequency circuit areproposed in this paper. The former is used to avoid thelarge switching current at the start up of the converterand the latter is utilized to reduce the EMI of theconverter.
Fast-Scale and Slow-Scale Subharmonic Oscillation of Valley Current-Mode Controlled Buck Converter
Institute of Scientific and Technical Information of China (English)
ZHOU Guo-Hua; XU Jian-Ping; BAO Bo-Cheng; ZHANG Fei; LIU Xue-Shan
2010-01-01
@@ A valley current-mode (VCM) controlled buck converter with current source load (CSI) has complex phenomena of fast-scale and slow-scale subharmonic oscillations.The piecewise smooth switching model of the VCM controlled buck converter with CSI is established.It is found that attractive regions of fast-scale and slow-scale subharmonic oscillations exist in the bifurcation diagram,and two tori exist in the corresponding Poincaré mapping.The research results by time-domain simulation indicate that U-type subharmonic oscillation (SO) constituted by SO and frequency-reduced subharmonic oscillation (FSO) exists in inductor current,and sine-type SO constituted by fast scale and low scaie exists in output voltage respectively.Experimental results are given to verify the analysis and simulation results.
Electronically Tunable Current-mode High-order Ladder Low-pass Filters Based on CMOS Technology
Directory of Open Access Journals (Sweden)
T. Kunto
2015-12-01
Full Text Available This paper describes the design of current mode low-pass ladder filters based on CMOS technology. The filters are derived from passive RLC ladder filter prototypes using new CMOS lossy and lossless integrators. The all-pole and Elliptic approximations are used in the proposed low-pass filter realizations. The proposed two types of filter can be electronically tuned between 10kHz and 100MHz through bias current from 0.03µA to 300µA. The proposed filters use 1.5 V power supply with 3 mW power consumption at 300 µA bias current. The proposed filters are resistorless, use grounded capacitors and are suitable for further integration. The total harmonic distortion (THD of the low-pass filters is less than 1% over the operating frequency range. PSPICE simulation results, obtained by using TSMC 0.18µm technology, confirm the presented theory.
Kirk, A; Harrison, J R; Militello, F; Walkden, N R
2016-01-01
Clear filamentary structures are observed at the edge of tokamak plasmas. These filaments are ejected out radially and carry plasma in the far Scrape Off Layer (SOL) region, where they are responsible for producing most of the transport. A study has been performed of the characteristics of the filaments observed in L-mode plasma on MAST, using visible imaging. A comparison has then been made with the observed particle and power profiles obtained at the divertor as a function of the plasma current. The radial velocity and to a lesser extent the radial size of the filaments are found to decrease as the plasma current is increased at constant density and input power. The results obtained in this paper on the dependence of the average filament dynamics on plasma current are consistent with the idea that the filaments are responsible for determining the particle profiles at the divertor.
Bi-directional high-side current sense circuit for switch mode power supplies
DEFF Research Database (Denmark)
Ekhtiari, Marzieh; Bruun, Erik; Andersen, Michael A. E.;
2014-01-01
and secondary sides of the transformer which is internally implemented inside the transformer. Therefore, curren t must be measured from the high voltage line in the presence of hig h input switching voltage. This paper proposes a resistive current s ensing circuit based on discrete components useful for input...
Coupling impedances of small discontinuities: A general approach
Kurennoy, Sergey S.; Gluckstern, Robert L.; Stupakov, Gennady V.
1995-10-01
A general theory of the beam interaction with small discontinuities of the vacuum chamber of an accelerator is developed taking into account the reaction of radiated waves back on the discontinuity. The reactive impedance calculated earlier is reproduced as the first order and the resistive one as the second order of a perturbation theory based on this general approach. The theory also gives, in an easy and natural way, the analytical results for the frequencies and coupling impedances of the trapped modes due to small discontinuities on the vacuum chamber of a general cross section. Formulas for two important particular cases-a circular and a rectangular chamber-are presented.
Coupling impedances of small discontinuities: A general approach
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S.S.; Gluckstern, R.L. [Physics Department, University of Maryland, College Park, Maryland 20742 (United States); Stupakov, G.V. [Stanford Linear Accelerator Center, Stanford, California 94309 (United States)
1995-10-01
A general theory of the beam interaction with small discontinuities of the vacuum chamber of an accelerator is developed taking into account the reaction of radiated waves back on the discontinuity. The reactive impedance calculated earlier is reproduced as the first order and the resistive one as the second order of a perturbation theory based on this general approach. The theory also gives, in an easy and natural way, the analytical results for the frequencies and coupling impedances of the trapped modes due to small discontinuities on the vacuum chamber of a general cross section. Formulas for two important particular cases---a circular and a rectangular chamber---are presented.
Energy Technology Data Exchange (ETDEWEB)
Ekedahl, Annika, E-mail: annika.ekedahl@cea.fr; Bourdelle, Clarisse; Artaud, Jean-François; Bernard, Jean-Michel; Bufferand, Hugo; Colas, Laurent; Decker, Joan; Delpech, Léna; Dumont, Rémi; Goniche, Marc; Helou, Walid; Hillairet, Julien; Lombard, Gilles; Magne, Roland; Mollard, Patrick; Nardon, Eric; Peysson, Yves; Tsitrone, Emmanuelle [CEA, IRFM, F-13108 Saint Paul-lez-Durance (France)
2015-12-10
The longstanding expertise of the Tore Supra team in long pulse heating and current drive with radiofrequency (RF) systems will now be exploited in the WEST device (tungsten-W Environment in Steady-state Tokamak) [1]. WEST will allow an integrated long pulse tokamak programme for testing W-divertor components at ITER-relevant heat flux (10-20 MW/m{sup 2}), while treating crucial aspects for ITER-operation, such as avoidance of W-accumulation in long discharges, monitoring and control of heat fluxes on the metallic plasma facing components (PFCs) and coupling of RF waves in H-mode plasmas. Scenario modelling using the METIS-code shows that ITER-relevant heat fluxes are compatible with the sustainment of long pulse H-mode discharges, at high power (up to 15 MW / 30 s at I{sub P} = 0.8 MA) or high fluence (up to 10 MW / 1000 s at I{sub P} = 0.6 MA) [2], all based on RF heating and current drive using Ion Cyclotron Resonance Heating (ICRH) and Lower Hybrid Current Drive (LHCD). This paper gives a description of the ICRH and LHCD systems in WEST, together with the modelling of the power deposition of the RF waves in the WEST-scenarios.
Vachon, Vincent; Laprade, Raynald; Schwartz, Jean-Louis
2012-09-15
Bacillus thuringiensis (Bt) Cry toxins constitute the active ingredient in the most widely used biological insecticides and insect-resistant transgenic crops. A clear understanding of their mode of action is necessary for improving these products and ensuring their continued use. Accordingly, a long history of intensive research has established that their toxic effect is due primarily to their ability to form pores in the plasma membrane of the midgut epithelial cells of susceptible insects. In recent years, a rather elaborate model involving the sequential binding of the toxins to different membrane receptors has been developed to describe the events leading to membrane insertion and pore formation. However, it was also proposed recently that, in contradiction with this mechanism, Bt toxins function by activating certain intracellular signaling pathways which lead to the necrotic death of their target cells without the need for pore formation. Because work in this field has largely focused, for several years, on the elaboration and promotion of these two models, the present revue examines in detail the experimental evidence on which they are based. It is concluded that the presently available information still supports the notion that Bt Cry toxins act by forming pores, but most events leading to their formation, following binding of the activated toxins to their receptors, remain relatively poorly understood.
Inhibition of cardiac Kv1.5 potassium current by the anesthetic midazolam: mode of action
Directory of Open Access Journals (Sweden)
Vonderlin N
2014-11-01
Full Text Available Nadine Vonderlin,1 Fathima Fischer,1 Edgar Zitron,1,2 Claudia Seyler,1 Daniel Scherer,1 Dierk Thomas,1,2 Hugo A Katus,1,2 Eberhard P Scholz1 1Department of Internal Medicine III, University Hospital Heidelberg, Heidelberg, Germany; 2German Centre for Cardiovascular Research (DZHK, Partner Site Heidelberg/Mannheim, Heidelberg, GermanyAbstract: Midazolam is a short-acting benzodiazepine that is widely used in anesthesia. Despite its widespread clinical use, detailed information about cardiac side effects of midazolam is largely lacking. Using the double-electrode voltage clamp technique, we studied pharmacological effects of midazolam on heterologously expressed Kv1.5 channels underlying atrial repolarizing current IKur. Midazolam dose-dependently inhibited Kv1.5 current, yielding an IC50 of 17 µM in an HEK cell line and an IC50 of 104 µM in Xenopus oocytes. We further showed that midazolam did not affect the half-maximal activation voltage of Kv1.5 channels. However, a small negative shift of the inactivation curve could be observed. Midazolam acted as a typical open-channel inhibitor with rapid onset of block and without frequency dependence of block. Taken together, midazolam is an open channel inhibitor of cardiac Kv1.5 channels. These data add to the current understanding of the pharmacological profile of midazolam.Keywords: anesthetics, potassium channels, pharmacology
Inhibition of cardiac Kv1.5 potassium current by the anesthetic midazolam: mode of action
Vonderlin, Nadine; Fischer, Fathima; Zitron, Edgar; Seyler, Claudia; Scherer, Daniel; Thomas, Dierk; Katus, Hugo A; Scholz, Eberhard P
2014-01-01
Midazolam is a short-acting benzodiazepine that is widely used in anesthesia. Despite its widespread clinical use, detailed information about cardiac side effects of midazolam is largely lacking. Using the double-electrode voltage clamp technique, we studied pharmacological effects of midazolam on heterologously expressed Kv1.5 channels underlying atrial repolarizing current IKur. Midazolam dose-dependently inhibited Kv1.5 current, yielding an IC50 of 17 μM in an HEK cell line and an IC50 of 104 μM in Xenopus oocytes. We further showed that midazolam did not affect the half-maximal activation voltage of Kv1.5 channels. However, a small negative shift of the inactivation curve could be observed. Midazolam acted as a typical open-channel inhibitor with rapid onset of block and without frequency dependence of block. Taken together, midazolam is an open channel inhibitor of cardiac Kv1.5 channels. These data add to the current understanding of the pharmacological profile of midazolam. PMID:25422586
Discontinuous Electromagnetic Fields Using Huygens Sources For Wavefront Manipulation
Selvanayagam, Michael
2013-01-01
We introduce the idea of discontinuous electric and magnetic fields at a boundary to design and shape wavefronts in an arbitrary manner. To create this discontinuity in the field we use electric and magnetic currents which act like a Huygens source to radiate the desired wavefront. These currents can be synthesized either by an array of electric and magnetic dipoles or by a combined impedance and admittance surface. A dipole array is an active implementation to impose discontinuous fields while the impedance/admittance surface acts as a passive one. We then expand on our previous work showing how electric and magnetic dipole arrays can be used to cloak an object demonstrating two novel cloaking schemes. We also show how to arbitrarily refract a beam using a set of impedance and admittance surfaces. Refraction using the idea of discontinuous fields is shown to be a more general case of refraction using phase discontinuities.
Directory of Open Access Journals (Sweden)
J. Bajer
2011-04-01
Full Text Available The paper deals with a pair of current-mode sine-wave oscillator circuits. Both these circuits are implemented using positive second-generation current conveyors (CCII+. The principle of the first oscillator is based on a conventional Wien-bridge network. However, this implementation suffers from the use of a floating capacitor, which can be unacceptable in the case of on-chip integration. This drawback is solved in the second variant via a slight modification of the Wien-bridge network, which then allows the use of all capacitors grounded. The modified circuit version was manufactured by means of the socalled diamond transistors, which play the role of CCII+ active building blocks. The circuit behavior was analyzed theoretically, with particular emphasis on the identification of real effects and their elimination, and subsequently verified experimentally. The experimental results are included in the paper.
Institute of Scientific and Technical Information of China (English)
ZHANG Linli; XU Bingyin; XUE Yongduan; GAO Houlei
2012-01-01
Non-solidly earthed systems are widely used for middle voltage distribution network at home and abroad. Fault point location especially the single phase-to-earth fault is very difficult because the fault current is very weak and the fault arc is intermittent. Although several methods have been developed, the problem of fault location has not yet been resolved very well. A new fault location method based on transient component of line voltage and 0-mode current is presented in this paper, which can realize fault section location by the feeder automation （FA） system. Line voltage signal can be obtained conveniently without requiring any additional equipment. This method is based on transient information, not affected by arc suppression coil.
Sérazin, Guillaume; Penduff, Thierry; Terray, Laurent; Grégorio, Sandy; Barnier, Bernard; Molines, Jean-Marc
2015-04-01
Ocean-atmosphere heat fluxes are particularly strong in Western Boundary Current (WBC) regions where SST front variations influence basin-scale climate variability. Observed low-frequency fluctuations in latitude and strength of these oceanic jets are classically thought to be essentially atmospherically-driven by wind stress curl variability via the oceanic Rossby wave adjustment. Yet academic eddy-resolving process-oriented models with double-gyre configurations have revealed that an idealized WBC may exhibit low-frequency intrinsic fluctuations without low-frequency external forcing (e.g. Berloff et al., 2007, Dijkstra and Ghil, 2005, etc). Experiments with eddying Ocean General Circulation Models (OGCMs) have also shown that the amount of low-frequency Sea Level Anomaly (SLA) variability is largely intrinsic in WBCs (Penduff et al. 2011; Sérazin et al 2014) and that the frontal-scale (<10°) pattern of the Kuroshio Extension (KE) variability is similar to intrinsic modes (Taguchi et al. 2010). Based on a pair of atmospherically-forced 1/12° OGCM experiments that simulate with accuracy either the intrinsic variability (seasonally-forced) or the observed total variability (forced with the full range of atmospheric timescales), Empirical Orthogonal Function analysis is performed on zonally-averaged SLA fields of four main WBCs (e.g. Gulf Stream, Kuroshio Extension, Agulhas Current and East Australian Current). The first two modes of the KE and GS exhibit a similar spatial structure that is shaped by oceanic intrinsic processes. The frequency content is however different between the intrinsic and total Principal Components, the former containing a wide range of timescales similar to a red noise and the latter being more autocorrelated at interannual-to-decadal timescales. These modes are compared with those obtained from the 20 years of altimetry observation and relationships with low-frequency westward propagative features in the respective oceanic basin are
A Current Mode Energy-Resolved CT Using Several Kinds of Scintillators
Hamaguchi, Takumi; Kanno, Ikuo; Hotta, Kazuhiro; Nakamura, Masaaki; Adachi, Ryuji
For computed tomography (CT) with the energy information of X-rays (energy-resolved CT), the authors have been developed a new detector system, "transXend" detector. The transXend detector measures X-rays as electric current and gives energy distribution after analysis. To apply the principle of the transXend detector for the use of fan or cone beam X-rays, the authors have reported two-dimensional transXend detector using stripe metal absorbers and a flat panel detector (FPD). In this paper, the energy-resolved CT is demonstrated using a FPD with different kinds of scintillator plates. Next, the possibility of using a scintillator plate which consists of various stripe scintillators instead of stripe metal absorbers for a two-dimensional transXend detector is shown.
Analysis of Discontinuity Induced Bifurcations in a Dual Input DC-DC Converter
Giaouris, Damian; Banerjee, Soumitro; Mandal, Kuntal; Al-Hindawi, Mohammed M.; Abusorrah, Abdullah; Al-Turki, Yusuf; El Aroudi, Abdelali
DC-DC power converters with multiple inputs and a single output are used in numerous applications where multiple sources, e.g. two or more renewable energy sources and/or a battery, feed a single load. In this work, a classical boost converter topology with two input branches connected to two different sources is chosen, with each branch independently being controlled by a separate peak current mode controller. We demonstrate for the first time that even though this converter is similar to other well known topologies that have been studied before, it exhibits many complex nonlinear behaviors that are not found in any other standard PWM controlled power converter. The system undergoes period incrementing cascade as a parameter is varied, with discontinuous hard transitions between consecutive periodicities. We show that the system can be described by a discontinuous map, which explains the observed bifurcation phenomena. The results have been experimentally validated.
A current-mode DC-DC buck converter with adaptive zero compensation
Institute of Scientific and Technical Information of China (English)
Yang Ling; Dai Guoding; Xu Chongwei; Liu Yuezhi
2013-01-01
To achieve fast transient response for a DC-DC buck converter,an adaptive zero compensation circuit is presented.The compensation resistance is dynamically adjusted according to the different output load conditions,and achieves an adequate system phase margin under the different conditions.An improved capacitor multiplier circuit is adopted to realize the minimized compensation capacitance size.In addition,analysis of the small-signal model shows the correctness of the mechanism of the proposed adaptive zero compensation technique.A currentmode DC-DC buck converter with the proposed structure has been implemented in a 0.35 μm CMOS process,and the die size is only 800 × 1040 μm2.The experimental results show that the transient undershoot/overshoot voltage and the recovery times do not exceed 40 mV and 30 μs for a load current variation from 100 mA to 1 A.
Multiple modes of clearing one's mind of current thoughts: overlapping and distinct neural systems.
Banich, Marie T; Mackiewicz Seghete, Kristen L; Depue, Brendan E; Burgess, Gregory C
2015-03-01
This study used the power of neuroimaging to identify the neural systems that remove information from working memory, a thorny issue to examine because it is difficult to confirm that individuals have actually modified their thoughts. To overcome this problem, brain activation as measured via fMRI was assessed when individuals had to clear their mind of all thought (global clear), clear their mind of a particular thought (targeted clear), or replace the current thought (replace), relative to maintaining an item in working memory. The pattern of activity in posterior sensory regions across these conditions confirmed compliance with task demands. A hierarchy of brain regions involved in cognitive control, including parietal, dorsolateral prefrontal and frontopolar regions, were engaged to varying degrees depending on the manner in which information was removed from working memory. In addition, individuals with greater difficulty in controlling internal thoughts exhibited greater activity in prefrontal brain regions associated with cognitive control, as well as in left lateral prefrontal areas including Broca's area, which is associated with inner speech. Copyright © 2015 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
SINGH Alka
2012-10-01
Full Text Available Use of distributed resources is growing in developing countries like India and in developed nations too. The increased acceptance of suchresources is mainly due to their modularity, increased reliability, good power quality and environment friendly operation. These are currently being interfaced to the existing systems using voltage source inverters (VSC’s. The control of such distributed resources is significantly different than the conventional power systems mainly because the VSC’s have no inertia unlike the synchronous generators.This paper deals with the Matlab modeling and design of control aspects of one such distributed source feeding a common load. A grid connected supply is also available. The control algorithm is developed for real and reactive power sharing of the load between thedistributed source and the grid. The developed control scheme is tested for linear (R-L load as well as nonlinear loads. With suitable modifications, the control algorithm can be extended for several distributed resources connected in parallel.
Energy Technology Data Exchange (ETDEWEB)
Harzalla, S., E-mail: harzallahozil@yahoo.fr; Chabaat, M., E-mail: mchabaat@yahoo.com [Built Environmental Research Laboratory, Civil Engineering Faculty, University of Sciences and Technology Houari Boumediene, B.P. 32 El Alia Bab-Ezzouar, Algiers 16111 (Algeria); Belgacem, F. Bin Muhammad, E-mail: fbmbelgacem@gmail.com [Department of Mathematics, Faculty of Basic Education, PAAET, Al-Aardhia (Kuwait)
2014-12-10
In this paper, a nondestructive technique is used as a tool to control cracks and microcracks in materials. A simulation by a numerical approach such as the finite element method is employed to detect cracks and eventually; to study their propagation using a crucial parameter such as the stress intensity factor. This approach has been used in the aircraft industry to control cracks. Besides, it makes it possible to highlight the defects of parts while preserving the integrity of the controlled products. On the other side, it is proven that the reliability of the control of defects gives convincing results for the improvement of the quality and the safety of the material. Eddy current testing (ECT) is a standard technique in industry for the detection of surface breaking flaws in magnetic materials such as steels. In this context, simulation tools can be used to improve the understanding of experimental signals, optimize the design of sensors or evaluate the performance of ECT procedures. CEA-LIST has developed for many years semi-analytical models embedded into the simulation platform CIVA dedicated to non-destructive testing. The developments presented herein address the case of flaws located inside a planar and magnetic medium. Simulation results are obtained through the application of the Volume Integral Method (VIM). When considering the ECT of a single flaw, a system of two differential equations is derived from Maxwell equations. The numerical resolution of the system is carried out using the classical Galerkin variant of the Method of Moments. Besides, a probe response is calculated by application of the Lorentz reciprocity theorem. Finally, the approach itself as well as comparisons between simulation results and measured data are presented.
Testing discontinuities in nonparametric regression
Dai, Wenlin
2017-01-19
In nonparametric regression, it is often needed to detect whether there are jump discontinuities in the mean function. In this paper, we revisit the difference-based method in [13 H.-G. Müller and U. Stadtmüller, Discontinuous versus smooth regression, Ann. Stat. 27 (1999), pp. 299–337. doi: 10.1214/aos/1018031100
Clopidogrel discontinuation after myocardial infarction and risk of thrombosis
DEFF Research Database (Denmark)
Charlot, Mette; Nielsen, Lars Hougaard; Lindhardsen, Jesper
2012-01-01
The benefit of extending clopidogrel treatment beyond the 12-month period recommended in current guidelines after myocardial infarction (MI) is debated. We analysed the risk of adverse cardiovascular outcomes after discontinuation of 12 months of clopidogrel treatment.......The benefit of extending clopidogrel treatment beyond the 12-month period recommended in current guidelines after myocardial infarction (MI) is debated. We analysed the risk of adverse cardiovascular outcomes after discontinuation of 12 months of clopidogrel treatment....
Energy Technology Data Exchange (ETDEWEB)
Grosdidier, T., E-mail: Thierry.grosdidier@univ-metz.f [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), Universite Paul Verlaine-Metz, Ile du Saulcy, 57045 Metz (France); Lab of Materials Modification by Laser, Ion and Electron Beams and School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Zou, J.X. [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), Universite Paul Verlaine-Metz, Ile du Saulcy, 57045 Metz (France); Bolle, B. [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), ENIM, Ile du Saulcy, 57045 Metz (France); Hao, S.Z.; Dong, C. [Lab of Materials Modification by Laser, Ion and Electron Beams and School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China)
2010-08-15
High current pulsed electron beam is a recently developed technique for surface modification. The pulsed electron irradiation introduces concentrated energy depositions in the thin surface layer of the treated materials, giving rise to an extremely fast heating and subsequent rapid cooling of the surface together with the formation of dynamic stress waves. Improved surface properties (hardness, corrosion resistance) can be obtained under the 'melting' mode when the top surface is melted and rapidly solidified (10{sup 7} K/s). In steels, this is essentially the result of nanostructures formed from the highly undercooled melt, melt surface purification, strain hardening induced by the thermal stress waves as well as metastable phase selections in the rapidly solidified melted layers. The use of the 'heating' mode is less conventional, combining effects of the heavy deformation and recrystallization/recovery mechanisms. A detailed analysis of a FeAl alloy demonstrates grain size refinement, hardening, solid-state enhanced diffusion and texture modification without modification of the surface geometry.
Cai, Guowei; Liu, Cheng; Yang, Deyou
2013-11-01
The doubly fed induction generators (DFIG) have been recognized as the dominant technology used in wind power generation systems with the rapid development of wind power. However, continuous operation of DFIG may cause a serious wind turbine generators tripping accident, due to destructive over-current in the rotor winding which is caused by the power system fault or inefficient fault ride-through (FRT) strategy. A new rotor current control scheme in the rotor-side converter (RSC) ispresented to enhance FRT capacities of grid-connected DFIG. Due to the strongly nonlinear nature of DFIG and insensitive to DFIG parameter's variations, a novel sliding mode controller was designed. The controller combines extended state observer (ESO) with sliding model variable structure control theory. The simulation is carried out to verify the effectiveness of the proposed control approach under various types of grid disturbances. It is shown that the proposed controller provides enhanced transient features than the classic proportional-integral control. The proposed control method can effectively reduce over-current in the RSC, and the transient pulse value of electromagnetic torque is too large under power grid fault.
Field current tracing control of a BSG based on sliding mode current observer%BSG电机励磁电流观测器跟踪控制
Institute of Scientific and Technical Information of China (English)
余腾伟; 王旭东
2011-01-01
Aiming at the nonlinearities of belt driven starter generator' s (BSG) excitation winding driving circuit and a variety of interference outside the engine compartment, making it difficult for conventional PWM strategy to achieve the optimal output current. According to the sliding mode control theory, a sliding mode observer approach is proposed, and the mathematical module of BSG field windings' driven system is established, utilizing advantages that including good control robustness to conduct online setting. Simulation and experimental results show that the step response time is about 10 ms, and the maximum overshoot is less than 5% . What' s more, the method enhances the systems self adaptive capacity, improves the startup performance of BSG-hybrid cars, and has good current tracking performance, and low costing.%针对弱混合动力汽车中带式驱动启动发电机(BSG)的励磁绕组驱动电路存在的非线性问题,以及发动机舱各种外部干扰导致传统的PWM技术难以使控制电流输出达到最优的问题,依据滑模变结构控制理论,采用电流观测器的方法,建立BSG电机励磁绕组驱动系统的数学模型,给出电流观测器的控制算法,利用滑模变结构控制鲁棒性好的优势对BSG电机励磁电流进行在线整定.仿真和试验结果表明,该方法的阶跃响应时间为10 ms,跟踪电流最大超调小于5％,增强了系统的自适应能力,提高了BSG混合动力轿车启动性能,并且具有较好的电流跟踪效果,降低了成本.
Institute of Scientific and Technical Information of China (English)
Jie Binbin; Sah Chih-Tang
2009-01-01
This paper reports the DC steady-state current-voltage and conductance-voltage characteristics of a Bipolar Field-Effect Transistor (BiFET) under the unipolar (electron) current mode of operation, with bipolar (elec-tron and hole) charge distributions considered. The model BiFET example presented has two MOS-gates on the two surfaces of a thin pure silicon base layer with electron and hole contacts on both edges of the thin base. The hole contacts on both edges of the thin pure base layer are grounded to give zero hole current. This 1-transistor analog-RF Basic Building Block nMOS amplifier circuit, operated in the unipolar current mode, complements the 1-transistor digital Basic Build Block CMOS voltage inverter circuit, operated in the bipolar-current mode just presented by us.
Directory of Open Access Journals (Sweden)
Rachid Askour
2014-05-01
Full Text Available In this paper, experimental results of 3-phase permanent magnet synchronous motor (PMSM sensorless speed control are presented. To estimate the rotor position, a sliding mode current observer (SMCO was implemented. This observer estimates the back emfs of the motor in the stationary reference frame using only the measured voltages and currents of the motor. These emfs were utilized to obtain the rotor position. The speed of the motor was calculated by differentiating the rotor position angle. The stability of the proposed SMCO was verified using Lyapunov method to determine the observer gain. The saturation function was adopted in order to reduce the chattering phenomenon caused by the SMCO. A vector control method was employed to achieve the sensorless drive system. The control application was developed in C/C++ language and implemented using the Texas Instruments TMS320LF2812 digital signal processor (DSP. This new processor enables intelligent control for motors. We used to test the drive the MCK2812 which is a professional development kit available from Technosoft Company. The theoretical finding is validated with experimental results that show the effectiveness of the real-time implementation.
Gorospe, Alking; Bautista, Zhierwinjay; Shin, Hyung-Seop
2016-10-01
Coated conductor (CC) tapes utilized in high-current-density superconducting cables are commonly subjected to different loading modes, primarily torsion and tension especially in the case of twisted stacked-tape cable. Torsion load can occur due to twisting along the length or when winding the CC tapes around a former, while tension load can occur due to pre-tension when coiled and as a hoop stress when the coil is energized. In this study, electromechanical properties of single CC tapes under torsion load were investigated using a new test apparatus. The results could provide basic information for cable designers to fully characterize stacked cables. Copper-electroplated and brass-laminated CC tapes fabricated with different deposition techniques were subjected to pure torsion and combined tension-torsion loading. The critical current, I c degradation behaviours of CC tapes under torsional deformation were examined. Also, the effect of further external lamination on the I c degradation behaviour of the CC tapes under such loading conditions was investigated. In the case of the combined tension-torsion test, short samples were subjected to twist pitches of 200 mm and 100 mm. Critical parameters including reversible axial stress and strain in such twist pitch conditions were also investigated.
MHD discontinuities in solar flares: continuous transitions and plasma heating
Ledentsov, Leonid; Somov, Boris
The conservation laws on a surface of discontinuity in the ideal magnetohydrodynamics (MHD) allow changing a discontinuity type with gradual (continuous) changes in conditions of plasma. Then there are the so-called transition solutions that satisfy simultaneously two types of discontinuities. We obtain all transition solutions on the basis of a complete system of boundary conditions for the MHD equations. We also found an expression describing a jump of internal energy of the plasma flowing through the discontinuity. It allows, firstly, to construct a generalized scheme of possible transitions between MHD discontinuities, and secondly, to examine the dependence of plasma heating by plasma density and configuration of the magnetic field near the surface of the discontinuity (i.e., by the type of the MHD discontinuity). The problem of the heating of "superhot" plasma (with the electron temperature is greater than 10 keV) in solar flares are discussed. It is shown that the best conditions for heating are carried out in the vicinity of the reconnecting current layer near the areas of reverse currents. Bibl.: B.V.Somov. Plasma Astrophysics, Part II: Reconnection and Flares, Second Edition. (New York: Springer SBM, 2013).
Mixing of discontinuously deforming media
Smith, Lachlan D; Lester, Daniel R; Metcalfe, Guy
2016-01-01
Mixing of materials is fundamental to many natural phenomena and engineering applications. The presence of discontinuous deformations - such as shear banding or wall slip - creates new mechanisms for mixing and transport beyond those predicted by classical dynamical systems theory. Here we show how a novel mixing mechanism combining stretching with cutting and shuffling yields exponential mixing rates, quantified by a positive Lyapunov exponent, an impossibility for systems with cutting and shuffling alone or bounded systems with stretching alone, and demonstrate it in a fluid flow. While dynamical systems theory provides a framework for understanding mixing in smoothly deforming media, a theory of discontinuous mixing is yet to be fully developed. New methods are needed to systematize, explain and extrapolate measurements on systems with discontinuous deformations. Here we investigate 'webs' of Lagrangian discontinuities and show that they provide a template for the overall transport dynamics. Considering sl...
Zhao, MingHao; Pan, YiBo; Fan, CuiYing; Xu, GuangTao
2017-08-01
The extended displacement discontinuities method has previously been used for crack analysis of elastic materials, piezoelectric media, magneto-electro-elastic media and piezoelectric semiconductors. Here, this method is extended to study cracks in two-dimensional n-type thermal piezoelectric semiconductors. The extended displacement discontinuities include the conventional displacement discontinuity, electric potential discontinuity, carrier density discontinuity, as well as temperature discontinuity across crack faces; correspondingly, the extended stresses represent conventional stress, electric displacement, electric current, and heat flux. Employing a Fourier transform, the fundamental solutions for a line crack under uniformly distributed extended displacement discontinuities on the crack faces are derived under mechanical, electrical, and heat loading. Based on the obtained fundamental solutions, an extended displacement discontinuity boundary element method is developed. The stress and heat flux intensity factors at the crack tip are calculated under different combined loadings.
Khayamy, Mehdy; Ojo, Olorunfemi
2015-04-01
A current source inverter fed from photovoltaic cells is proposed to power an autonomous load when operating under either power regulation or voltage and frequency drooping modes. Input-output linearization technique is applied to the overall nonlinear system to achieve a globally stable system under feasible operating conditions. After obtaining the steady-state model that demarcates the modes of operation, computer Simulation results for variations in irradiance and the load power of the controlled system are generated in which an acceptable dynamic response of the power generator system under the two modes of operation is observed.
Energy Technology Data Exchange (ETDEWEB)
Eitan, M.; Fowler, E.; Herrmann, R.; Duval, A.; Pelhate, M.; Zlotkin, E. (Hebrew Univ., Jerusalem (Israel))
1990-06-26
A new toxin, Lqh alpha IT, which caused a unique mode of paralysis of blowfly larvae, was purified from the venom of the scorpion Leiurus quinquestriatus hebraeus, and its structural and pharmacological properties were compared to those of three other groups of neurotoxins found in Buthinae scorpion venoms. Like the excitatory and depressant insect-selective neurotoxins, Lqh alpha IT was highly toxic to insects, but it differed from these toxins in two important characteristics: (a) Lqh alpha IT lacked strict selectivity for insects; it was highly toxic to crustaceans and had a measurable but low toxicity to mice. (b) It did not displace an excitatory insect toxin, 125I-AaIT, from its binding sites in the insect neuronal membrane; this indicates that the binding sites for Lqh alpha IT are different from those shared by the excitatory and depressant toxins. However, in its primary structure and its effect on excitable tissues, Lqh alpha IT strongly resembled the well-characterized alpha scorpion toxins, which affect mammals. The amino acid sequence was identical with alpha toxin sequences in 55%-75% of positions. This degree of similarity is comparable to that seen among the alpha toxins themselves. Voltage- and current-clamp studies showed that Lqh alpha IT caused an extreme prolongation of the action potential in both cockroach giant axon and rat skeletal muscle preparations as a result of the slowing and incomplete inactivation of the sodium currents. These observations indicate that Lqh alpha IT is an alpha toxin which acts on insect sodium channels.
Hammann, Simon; Englert, Michael; Müller, Marco; Vetter, Walter
2015-12-01
Triacylglycerols represent the major part (>90%) in most plant oils and have to be eliminated, when the minor compounds such as phytosterols or tocopherols should be analyzed. Here, we used an all liquid-liquid chromatographic technique, countercurrent chromatography (CCC), to fractionate the minor lipids before gas chromatography (GC) analysis. To cover the wide range of polarity of the minor compounds, we used the co-current mode, in which both mobile and stationary phase are pumped through the system. This allowed to elute substances which partitioned almost exclusively in the stationary phase within 90 min. After testing with standard compounds, the method was applied to the separation of sesame oil and sunflower oil samples. The abundant triacylglycerols could be effectively separated from tocopherols, phytosterols, diacylglycerols, and free fatty acids in the samples, and these compounds could be analyzed (after trimethylsilylation) by GC coupled with mass spectrometry. After the enrichment caused by the CCC fractionation, we were also able to identify the tocopherol derivative α-tocomonoenol, which had not been described in sunflower oil before. Also, separation of sesame oil yielded a mixture of the polar compounds sesamin and sesamolin without further impurities.
A 0.7 V, 40 nW Compact, Current-Mode Neural Spike Detector in 65 nm CMOS.
Yao, Enyi; Chen, Yi; Basu, Arindam
2016-04-01
In this paper, we describe a novel low power, compact, current-mode spike detector circuit for real-time neural recording systems where neural spikes or action potentials (AP) are of interest. Such a circuit can enable massive compression of data facilitating wireless transmission. This design can generate a high signal-to-noise ratio (SNR) output by approximating the popularly used nonlinear energy operator (NEO) through standard analog blocks. We show that a low pass filter after the NEO can be used for two functions-(i) estimate and cancel low frequency interference and (ii) estimate threshold for spike detection. The circuit is implemented in a 65 nm CMOS process and occupies 200 μm × 150 μ m of chip area. Operating from a 0.7 V power supply, it consumes about 30 nW of static power and 7 nW of dynamic power for 100 Hz input spike rate making it the lowest power consuming spike detector reported so far.
Ayten, B
2013-01-01
Due to the smallness of the volumes associated with the flux surfaces around the O-point of a magnetic island, the electron cyclotron power density applied inside the island for the stabilization of neoclassical tearing modes (NTMs) can exceed the threshold for non-linear effects as derived previously by Harvey et al, Phys. Rev. Lett. 62 (1989) 426. We study the non-linear electron cyclotron current drive (ECCD) efficiency through bounce-averaged, quasi-linear Fokker-Planck calculations in the magnetic geometry as created by the islands. The calculations are performed for the parameters of a typical NTM stabilization experiment on ASDEX Upgrade. A particular feature of these experiments is that the rays of the EC wave beam propagate tangential to the flux surfaces in the power deposition region. The calculations show significant non-linear effects on the ECCD efficiency, when the ECCD power is increased from its experimental value of 1 MW to a larger value of 4 MW. The nonlinear effects are largest in case of...
Current trends in studies on reverse-mode polymer dispersed liquid-crystal films — A review
Ahmad, Farzana; Jamil, M.; Jeon, Y. J.
2014-07-01
Reverse-mode polymer dispersed liquid crystals (PDLCs) comprise an important new class of materials for optical device applications. Generally reverse-mode PDLCs are transparent and opaque in the absence and presence of an external field, respectively. Display devices based on reverse-mode PDLC technology are useful for large-area displays; because their fabrication for manufacturing shutters is considered to be easier and faster, they are also employed for automotive technology and smart windows. These devices can be operated at a low voltage, which conserves energy in intelligent-device applications. This work presents a comprehensive review of past research regarding reverse-mode PDLCs and includes the advantageous features, applications, and various fabrication methods of reverse-mode PDLCs and photo-chromic reverse-mode PDLCs. In addition, some new features of this technology that have recently been reported and future investigations by a variety of research groups are presented.
Energy Technology Data Exchange (ETDEWEB)
Liu, Dongjian [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Southwestern Institution of Physics, Chengdu 610041 (China); Bao, Jian [Fusion Simulation Center, Peking University, Beijing 100871 (China); Han, Tao; Wang, Jiaqi [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Lin, Zhihong, E-mail: zhihongl@uci.edu [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States)
2016-02-15
A finite-mass electron fluid model for low frequency electromagnetic fluctuations, particularly the collisionless tearing mode, has been implemented in the gyrokinetic toroidal code. Using this fluid model, linear properties of the collisionless tearing mode have been verified. Simulations verify that the linear growth rate of the single collisionless tearing mode is proportional to D{sub e}{sup 2}, where D{sub e} is the electron skin depth. On the other hand, the growth rate of a double tearing mode is proportional to D{sub e} in the parameter regime of fusion plasmas.
Directory of Open Access Journals (Sweden)
D. Torres
2004-01-01
Full Text Available Se presenta un método enfocado a la síntesis de filtros activos en modo voltaje y modo corriente, modelados con amplificadores operacionales de transconductancia (OTAs, y capacitores. El OTA se sintetiza usando el dispositivo activo universal conocido como convector de corriente negativo de segunda generación (CCII-. Se aprovecha el valor de la impedancia parásita del CCII- para implementar la transconductancia del amplificador operacional. Se describe el procedimiento de transformación de una topología de modo voltaje a modo corriente y viceversa, así como la síntesis de filtros usando el CCII-. Se presentan resultados de simulación usando SPICE, para demostrar la confiabilidad del procedimiento de síntesis de filtros en modo voltaje y modo corriente usando el convector de corriente negativo de segunda generaciónA method focused on the synthesis of active filters both voltage mode type and current mode type, modeled by operational transconductance amplifiers (OTAs, and capacitors, is presented. The OTA is synthesized by using the universal active device known as negative second generation current conveyor (CCII-. The value of the parasitic impedance of the CCII- is used to implement the transconductance of the OTA. the procedure of transformation of a topology from voltage mode to current mode and viceversa, as well as the synthesis of filters by using the CCII-. Simulation results are presented by using SPICE, to demonstrate the suitability of the procedure for the synthesis of filters in voltage mode type and current mode type by using the CCII-.
Energy Technology Data Exchange (ETDEWEB)
Natsheh, Ammar N. [Faculty of Engineering, Al-Ahliyya Amman University, Post Code 19328 Amman (Jordan); Nazzal, Jamal M. [Faculty of Engineering, Al-Ahliyya Amman University, Post Code 19328 Amman (Jordan)]. E-mail: jnazzal@ammanu.edu.jo
2007-08-15
This work describes the bifurcational behavior of a modular peak current-mode controlled DC-DC boost converter with multi bifurcation parameters. The parallel-input/parallel-output converter consists of two identical boost circuits and operates in the continuous-current conduction mode (CCM). A nonlinear mapping in closed form is derived and bifurcation diagrams are generated using MATLAB. A comparison is made between the modular converter diagrams with those of the single boost converter. The effect of introducing mutual coupling between the inductors of the constituent modules is also addressed. Results are verified using the circuit analysis package PSPICE.
Quantitative Estimation of Transmitted and Reflected Lamb Waves at Discontinuity
Energy Technology Data Exchange (ETDEWEB)
Lim, Hyung Jin; Sohn, Hoon [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)
2010-08-15
For the application of Lamb wave to structural health monitoring(SHM), understanding its physical characteristic and interaction between Lamb wave and defect of the host structure is an important issue. In this study, reflected, transmitted and mode converted Lamb waves at discontinuity of a plate structure were simulated and the amplitude ratios are calculated theoretically using Modal decomposition method. The predicted results were verified comparing with finite element method(FEM) and experimental results simulating attached PZTs. The result shows that the theoretical prediction is close to the FEM and the experimental verification. Moreover, quantitative estimation method was suggested using amplitude ratio of Lamb wave at discontinuity
Mixing of discontinuously deforming media
Smith, L. D.; Rudman, M.; Lester, D. R.; Metcalfe, G.
2016-02-01
Mixing of materials is fundamental to many natural phenomena and engineering applications. The presence of discontinuous deformations—such as shear banding or wall slip—creates new mechanisms for mixing and transport beyond those predicted by classical dynamical systems theory. Here, we show how a novel mixing mechanism combining stretching with cutting and shuffling yields exponential mixing rates, quantified by a positive Lyapunov exponent, an impossibility for systems with cutting and shuffling alone or bounded systems with stretching alone, and demonstrate it in a fluid flow. While dynamical systems theory provides a framework for understanding mixing in smoothly deforming media, a theory of discontinuous mixing is yet to be fully developed. New methods are needed to systematize, explain, and extrapolate measurements on systems with discontinuous deformations. Here, we investigate "webs" of Lagrangian discontinuities and show that they provide a template for the overall transport dynamics. Considering slip deformations as the asymptotic limit of increasingly localised smooth shear, we also demonstrate exactly how some of the new structures introduced by discontinuous deformations are analogous to structures in smoothly deforming systems.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Sun, E-mail: szhang@pmo.ac.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Key Laboratory of Dark Matter and Space Astronomy, Chinese Academy of Sciences, Nanjing 210008 (China); Joint Center for Particle, Nuclear Physics and Cosmology (J-CPNPC), PMO-NJU, Nanjing 210008 (China)
2014-02-05
In this Letter, we have studied the shock wave and discontinuity propagation for relativistic superfluid with spontaneous U(1) symmetry breaking in the framework of hydrodynamics. General features of shock waves are provided, the propagation of discontinuity and the sound modes of shock waves are also presented. The first sound and the second sound are identified as the propagation of discontinuity, and the results are in agreement with earlier theoretical studies. Moreover, a differential equation, called the growth equation, is obtained to describe the decay and growth of the discontinuity propagating along its normal trajectory. The solution is in an integral form and special cases of diverging waves are also discussed.
Institute of Scientific and Technical Information of China (English)
郭亚军; 马大为; 王晓峰; 乐贵高
2011-01-01
An adaptive backstepping sliding mode control approach is introduced to control the pitch motion of a rocket launcher. Its control law is proposed to guarantee that the control system is ultimately bounded in a Lyapunov sense and make the servo system track the instruction of reference position globally and asymptotically. In addition, the sliding mode control can restrain the effects of parameter uncertainties and external disturbance. The functions of adaptive mechanism and sliding mode control are analyzed through the simulation in the different conditions. The simulation results illustrate that the method is applicable and robust.
de Bock, M. F. M.; Citrin, J.; Saarelma, S.; Temple, D.; Conway, N. J.; Kirk, A.; Meyer, H.; Michael, C. A.
2012-01-01
Edge localized modes (ELMs), that are present in most tokamak H-(high confinement) modes, can cause significant damage to plasma facing components in fusion reactors. Controlling ELMs is considered necessary and hence it is vital to understand the underlying physics. The stability of ELMs is typical
de Bock, M. F. M.; Citrin, J.; Saarelma, S.; Temple, D.; Conway, N. J.; Kirk, A.; Meyer, H.; Michael, C. A.
2012-01-01
Edge localized modes (ELMs), that are present in most tokamak H-(high confinement) modes, can cause significant damage to plasma facing components in fusion reactors. Controlling ELMs is considered necessary and hence it is vital to understand the underlying physics. The stability of ELMs is
A 1.4-V 48-μW current-mode front-end circuit for analog hearing aids with frequency compensation
Institute of Scientific and Technical Information of China (English)
Wang Xiaoyu; Yang Haigang; Li Fanyang; Yin Tao; Liu Fei
2012-01-01
A current-mode front-end circuit with low voltage and low power for analog hearing aids is presented.The circuit consists of a current-mode AGC (automatic gain control) and a current-mode adaptive filter.Compared with its conventional voltage-mode counterparts,the proposed front-end circuit has the identified features of frequency compensation based on the state space theory and continuous gain with an exponential characteristic.The frequency compensation which appears only in the DSP unit of the digital hearing aid can upgrade the performance of the analog hearing aid in the field of low-frequency hearing loss.The continuous gain should meet the requirement of any input amplitude level,while its exponential characteristic leads to a large input dynamic range in accordance with the dB SPL (sound pressure level).Furthermore,the front-end circuit also provides a discrete knee point and discrete compression ratio to allow for high calibration flexibility.These features can accommodate users whose ears have different pain thresholds.Taking advantage of the current-mode technique,the MOS transistors work in the subthreshold region so that the quiescent current is small.Moreover,the input current can be compressed to a low voltage signal for processing according to the compression principle from the current-domain to the voltage-domain.Therefore,the objective of low voltage and low power (48 μW at 1.4 V) can be easily achieved in a high threshold-voltage CMOS process of 0.35 μm (VToN + |Vrop｜≈ 1.35 V).The THD is below -45 dB.The fabricated chip only occupies the area of 1 × 0.5 mm2 and 1 × 1 mm2.
Calculation of Accurate Hexagonal Discontinuity Factors for PARCS
Energy Technology Data Exchange (ETDEWEB)
Pounders. J., Bandini, B. R. , Xu, Y, and Downar, T. J.
2007-11-01
In this study we derive a methodology for calculating discontinuity factors consistent with the Triangle-based Polynomial Expansion Nodal (TPEN) method implemented in PARCS for hexagonal reactor geometries. The accuracy of coarse-mesh nodal methods is greatly enhanced by permitting flux discontinuities at node boundaries, but the practice of calculating discontinuity factors from infinite-medium (zero-current) single bundle calculations may not be sufficiently accurate for more challenging problems in which there is a large amount of internodal neutron streaming. The authors therefore derive a TPEN-based method for calculating discontinuity factors that are exact with respect to generalized equivalence theory. The method is validated by reproducing the reference solution for a small hexagonal core.
The structure of rotational discontinuities
Energy Technology Data Exchange (ETDEWEB)
Neugebauer, M. (California Institute of Technology, Pasadena (USA))
1989-11-01
This study examines the structures of a set of rotational discontinuities detected in the solar wind by the ISEE-3 spacecraft. It is found that the complexity of the structure increases as the angle {theta} between the propagation vector k and the magnetic field decreases. For rotational discontinuities that propagate at a large angle to the field with an ion (left-hand) sense of rotation, the magnetic hodograms tend to be flattened, in agreement with prior numerical simulations. When {theta} is large, angular overshoots are often observed at one or both ends of the discontinuity. When the propagation is nearly parallel to the field (i.e., when {theta} is small), many different types of structure are seen, ranging from straight lines, the S-shaped curves, to complex, disorganized shapes.
Continuous, saturation, and discontinuous tokamak plasma vertical position control systems
Energy Technology Data Exchange (ETDEWEB)
Mitrishkin, Yuri V., E-mail: y_mitrishkin@hotmail.com [M. V. Lomonosov Moscow State University, Faculty of Physics, Moscow 119991 (Russian Federation); Pavlova, Evgeniia A., E-mail: janerigoler@mail.ru [M. V. Lomonosov Moscow State University, Faculty of Physics, Moscow 119991 (Russian Federation); Kuznetsov, Evgenii A., E-mail: ea.kuznetsov@mail.ru [Troitsk Institute for Innovation and Fusion Research, Moscow 142190 (Russian Federation); Gaydamaka, Kirill I., E-mail: k.gaydamaka@gmail.com [V. A. Trapeznikov Institute of Control Sciences of the Russian Academy of Sciences, Moscow 117997 (Russian Federation)
2016-10-15
Highlights: • Robust new linear state feedback control system for tokamak plasma vertical position. • Plasma vertical position relay control system with voltage inverter in sliding mode. • Design of full models of multiphase rectifier and voltage inverter. • First-order unit approximation of full multiphase rectifier model with high accuracy. • Wider range of unstable plant parameters of stable control system with multiphase rectifier. - Abstract: This paper is devoted to the design and comparison of unstable plasma vertical position control systems in the T-15 tokamak with the application of two types of actuators: a multiphase thyristor rectifier and a transistor voltage inverter. An unstable dynamic element obtained by the identification of plasma-physical DINA code was used as the plasma model. The simplest static feedback state space control law was synthesized as a linear combination of signals accessible to physical measurements, namely the plasma vertical displacement, the current, and the voltage in a horizontal field coil, to solve the pole placement problem for a closed-loop system. Only one system distinctive parameter was used to optimize the performance of the feedback system, viz., a multiple real pole. A first-order inertial unit was used as the rectifier model in the feedback. A system with a complete rectifier model was investigated as well. A system with the voltage inverter model and static linear controller was brought into a sliding mode. As this takes place, real time delays were taken into account in the discontinuous voltage inverter model. The comparison of the linear and sliding mode systems showed that the linear system enjoyed an essentially wider range of the plant model parameters where the feedback system was stable.
Energy Technology Data Exchange (ETDEWEB)
Gao, Yonghao [Department of Materials Science and Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Yerokhin, Aleksey, E-mail: a.yerokhin@sheffield.ac.uk [Department of Materials Science and Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); National University of Science and Technology “MISIS”, Leninsky Prospect, 4, Moscow 119049 (Russian Federation); Matthews, Allan [Department of Materials Science and Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)
2014-10-15
Highlights: • MgO-Na{sub 4}Ca(PO{sub 3}){sub 6} coatings produced on cp-Mg in both PUP- and PBP-PEO modes. • Negative biasing affects PEO processing of cp-Mg in Ca(OH){sub 2}-Na{sub 3}PO{sub 4} electrolyte. • Thicker and macro defect-free PUP-PEO coatings provide better corrosion protection. • Corrosion mechanisms of PEO-treated cp-Mg in SBF discussed. - Abstract: Plasma electrolytic oxidation (PEO) coatings were produced on commercially pure magnesium in a biologically friendly electrolyte composed of 2 g L{sup −1} Ca(OH){sub 2} and 12 g L{sup −1} Na{sub 3}PO{sub 4}·12H{sub 2}O using pulsed unipolar and bipolar current regimes with negative biasing varying from 0 to 20 mA cm{sup −2}. Analysis of voltage transients was performed to characterise the PEO processes. The coating morphology and phase composition were studied by scanning electron microscopy and X-ray diffraction technique, respectively. In vitro corrosion performance of the coatings was evaluated in a simulated body fluid at 37 ± 1 °C, using electrochemical techniques including open circuit potential monitoring, electrochemical impedance spectroscopy and potentiodynamic polarisation scans. The influence of the negative biasing on the PEO process and resulting coating characteristics is discussed. Unlike generally recognised beneficial effects of the negative biasing in PEO treatments of some other metal-electrolyte systems, it was found that detrimental effects are induced to the coatings on cp-Mg produced in the studied electrolyte when the negative current amplitude increases, which may be attributed to hydrogen liberation at the coating/substrate interface during the negative biasing cycles. As a result, a deterioration of vitro corrosion performance was observed for the pulsed bipolar PEO coatings compared to those produced using the pulsed unipolar regime which provides better quality coatings.
Anil Kumar Sharma; Dipankar Pal
2010-01-01
In this paper the current mode approach called “Current Conveyor (CCII+)” has been incorporated to design and simulate the circuit for producing two amplitude matched anti-phase sine waveforms which are frequently used in various communication and instrumentation systems. PSpice simulation has been used to depict the output waveforms. The power supply used is ±2.5 V which can be easily incorporated with CMOS IC technology. The designed circuit has been simulated at variousfrequency ranges and...
Constrained Optimization of Discontinuous Systems
Y.M. Ermoliev; V.I. Norkin
1996-01-01
In this paper we extend the results of Ermoliev, Norkin and Wets [8] and Ermoliev and Norkin [7] to the case of constrained discontinuous optimization problems. In contrast to [7] the attention is concentrated on the proof of general optimality conditions for problems with nonconvex feasible sets. Easily implementable random search technique is proposed.
Research progress on criteria for discontinuation of EGFR inhibitor therapy
Directory of Open Access Journals (Sweden)
Zhuang HQ
2012-10-01
Full Text Available Hong-qing Zhuang, Zhi-yong Yuan, Jun Wang, Ping Wang, Lu-jun Zhao, Bai-lin ZhangDepartment of Radiotherapy, Tianjin Medical University Cancer Institute and Hospital, Tianjin Key Laboratory of Cancer Prevention and Therapy, Tianjin Lung Cancer Center, Tianjin, People's Republic of ChinaAbstract: The clinical success of the epidermal growth factor receptor (EGFR tyrosine kinase inhibitors (TKI as therapeutic agents has prompted great interest in their further development and clinical testing for a wide variety of malignancies. However, most studies have focused on the efficacy of TKI, and few studies have been done on the criteria for their discontinuation. The current standard for drug discontinuation is “until progression”, based on change in tumor size. However, tumor size is not related to the gene expression which determines the efficacy of TKI in the final analysis, and it is also difficult to make a thorough and correct prediction based on tumor size when the TKI is discontinued. Nevertheless, clinical evaluation of the criteria for TKI discontinuation is still in its early days. Some promising findings have started to emerge. With the improving knowledge of EGFR and its inhibitors, it is expected that the criteria for discontinuation of EGFR inhibitor therapy will become clearer.Keywords: epidermal growth factor receptor, drug discontinuation, acquired drug-resistance
Minimizers with discontinuous velocities for the electromagnetic variational method
de Luca, Jayme
2010-08-01
The electromagnetic two-body problem has neutral differential delay equations of motion that, for generic boundary data, can have solutions with discontinuous derivatives. If one wants to use these neutral differential delay equations with arbitrary boundary data, solutions with discontinuous derivatives must be expected and allowed. Surprisingly, Wheeler-Feynman electrodynamics has a boundary value variational method for which minimizer trajectories with discontinuous derivatives are also expected, as we show here. The variational method defines continuous trajectories with piecewise defined velocities and accelerations, and electromagnetic fields defined by the Euler-Lagrange equations on trajectory points. Here we use the piecewise defined minimizers with the Liénard-Wierchert formulas to define generalized electromagnetic fields almost everywhere (but on sets of points of zero measure where the advanced/retarded velocities and/or accelerations are discontinuous). Along with this generalization we formulate the generalized absorber hypothesis that the far fields vanish asymptotically almost everywhere and show that localized orbits with far fields vanishing almost everywhere must have discontinuous velocities on sewing chains of breaking points. We give the general solution for localized orbits with vanishing far fields by solving a (linear) neutral differential delay equation for these far fields. We discuss the physics of orbits with discontinuous derivatives stressing the differences to the variational methods of classical mechanics and the existence of a spinorial four-current associated with the generalized variational electrodynamics.
Lecoanet, Daniel; Quataert, Eliot
2012-01-01
We study the effects of anisotropic thermal conduction along magnetic field lines on an accelerated contact discontinuity in a weakly collisional plasma. We first perform a linear stability analysis similar to that used to derive the Rayleigh-Taylor instability (RTI) dispersion relation. We find that anisotropic conduction is only important for compressible modes, as incompressible modes are isothermal. Modes grow faster in the presence of anisotropic conduction, but growth rates do not change by more than a factor of order unity. We next run fully non-linear numerical simulations of a contact discontinuity with anisotropic conduction. The non-linear evolution can be thought of as a superposition of three physical effects: temperature diffusion due to vertical conduction, the RTI, and the heat flux driven buoyancy instability (HBI). In simulations with RTI-stable contact discontinuities, the temperature discontinuity spreads due to vertical heat conduction. This occurs even for initially horizontal magnetic f...
Jayapalan, Kanesh K.; Chin, Oi-Hoong
2012-09-01
The H mode transition and maintenance currents in a 13.56 MHz laboratory 6 turn planar coil inductively coupled plasma (ICP) reactor are simulated for low pressure argon discharge range of 0.02-0.3 mbar with neutral gas heating and at ambient temperature. An experimentally fitted 3D power evolution plot for 0.02 mbar argon pressure is also shown to visualize the effects of hysteresis in the system. Comparisons between simulation and experimental measurements show good agreement in the pressure range of 0.02-0.3 mbar for transition currents and 0.02-0.1 mbar for maintenance currents only when neutral gas heating is considered. This suggests that neutral gas heating plays a non-negligible role in determining the mode transition points of a rf ICP system.
Zhongqi, Liu; Chun, Zhang; Yongming, Li; Zhihua, Wang
2010-06-01
This paper presents a current-mode voltage regulator for a passive UHF RFID transponder. The passive tag power is extracted from RF energy through the RF-to-DC rectifier. Due to huge variations of the incoming RF power, the rectifier output voltage should be regulated to achieve a stable power supply. By accurately controlling the current flowing into the load with an embedded sub-threshold reference, the regulated voltage varies in a range of 1-1.3 V from -20 to 80 °C, and a bandwidth of about 100 kHz is achieved for a fast power recovery. The circuit is fabricated in UMC 0.18 μm mixed-mode CMOS technology, and the current consumption is only 1 μA.
Energy Technology Data Exchange (ETDEWEB)
Aoki, Takashi; Nishikigouri, Kazuto; Gushiken, Tsutomu; Sano, Yoshinobu; Togashi, Tomohito [Accelerator Engineering Corp. Konakadai, Chiba (Japan); Kumada, Masayuki; Takada, Eiichi; Noda, Koji; Kanazawa, Mitsutaka
1997-12-31
We report a result of the ripple measurement in the by-pass resistor circuit of HIMAC synchrotron main magnet coils. The result shows clear separation of common- and normal- mode components in the frequency domain. An interpretation of the data and relevant characteristic of the method such as ripple sensitivity are discussed. (author)
Ayten, B.; Westerhof, E.; ASDEX Upgrade team,
2014-01-01
Due to the smallness of the volumes associated with the flux surfaces around the O-point of a magnetic island, the electron cyclotron power density applied inside the island for the stabilization of neoclassical tearing modes (NTMs) can exceed the threshold for non-linear effects as derived
Strategies for discontinuation of proton pump inhibitors
DEFF Research Database (Denmark)
Haastrup, Peter; Paulsen, Maja S; Begtrup, Luise M
2014-01-01
PURPOSE: Proton pump inhibitors (PPIs) are considered to be overprescribed. Consensus on how to attempt discontinuation is, however, lacking. We therefore conducted a systematic review of clinical studies on discontinuation of PPIs. METHODS: Systematic review based on clinical studies investigating...
Discontinuities in recurrent neural networks.
Gavaldá, R; Siegelmann, H T
1999-04-01
This article studies the computational power of various discontinuous real computational models that are based on the classical analog recurrent neural network (ARNN). This ARNN consists of finite number of neurons; each neuron computes a polynomial net function and a sigmoid-like continuous activation function. We introduce arithmetic networks as ARNN augmented with a few simple discontinuous (e.g., threshold or zero test) neurons. We argue that even with weights restricted to polynomial time computable reals, arithmetic networks are able to compute arbitrarily complex recursive functions. We identify many types of neural networks that are at least as powerful as arithmetic nets, some of which are not in fact discontinuous, but they boost other arithmetic operations in the net function (e.g., neurons that can use divisions and polynomial net functions inside sigmoid-like continuous activation functions). These arithmetic networks are equivalent to the Blum-Shub-Smale model, when the latter is restricted to a bounded number of registers. With respect to implementation on digital computers, we show that arithmetic networks with rational weights can be simulated with exponential precision, but even with polynomial-time computable real weights, arithmetic networks are not subject to any fixed precision bounds. This is in contrast with the ARNN that are known to demand precision that is linear in the computation time. When nontrivial periodic functions (e.g., fractional part, sine, tangent) are added to arithmetic networks, the resulting networks are computationally equivalent to a massively parallel machine. Thus, these highly discontinuous networks can solve the presumably intractable class of PSPACE-complete problems in polynomial time.
Koechl, F.; Loarte, A.; Parail, V.; Belo, P.; Brix, M.; Corrigan, G.; Harting, D.; Koskela, T.; Kukushkin, A. S.; Polevoi, A. R.; Romanelli, M.; Saibene, G.; Sartori, R.; Eich, T.; Contributors, JET
2017-08-01
The dynamics for the transition from L-mode to a stationary high Q DT H-mode regime in ITER is expected to be qualitatively different to present experiments. Differences may be caused by a low fuelling efficiency of recycling neutrals, that influence the post transition plasma density evolution on the one hand. On the other hand, the effect of the plasma density evolution itself both on the alpha heating power and the edge power flow required to sustain the H-mode confinement itself needs to be considered. This paper presents results of modelling studies of the transition to stationary high Q DT H-mode regime in ITER with the JINTRAC suite of codes, which include optimisation of the plasma density evolution to ensure a robust achievement of high Q DT regimes in ITER on the one hand and the avoidance of tungsten accumulation in this transient phase on the other hand. As a first step, the JINTRAC integrated models have been validated in fully predictive simulations (excluding core momentum transport which is prescribed) against core, pedestal and divertor plasma measurements in JET C-wall experiments for the transition from L-mode to stationary H-mode in partially ITER relevant conditions (highest achievable current and power, H 98,y ~ 1.0, low collisionality, comparable evolution in P net/P L-H, but different ρ *, T i/T e, Mach number and plasma composition compared to ITER expectations). The selection of transport models (core: NCLASS + Bohm/gyroBohm in L-mode/GLF23 in H-mode) was determined by a trade-off between model complexity and efficiency. Good agreement between code predictions and measured plasma parameters is obtained if anomalous heat and particle transport in the edge transport barrier are assumed to be reduced at different rates with increasing edge power flow normalised to the H-mode threshold; in particular the increase in edge plasma density is dominated by this edge transport reduction as the calculated neutral influx across the
Directory of Open Access Journals (Sweden)
Kasenda Benjamin
2012-08-01
Full Text Available Abstract Background Randomized controlled trials (RCTs may be discontinued because of apparent harm, benefit, or futility. Other RCTs are discontinued early because of insufficient recruitment. Trial discontinuation has ethical implications, because participants consent on the premise of contributing to new medical knowledge, Research Ethics Committees (RECs spend considerable effort reviewing study protocols, and limited resources for conducting research are wasted. Currently, little is known regarding the frequency and characteristics of discontinued RCTs. Methods/Design Our aims are, first, to determine the prevalence of RCT discontinuation for specific reasons; second, to determine whether the risk of RCT discontinuation for specific reasons differs between investigator- and industry-initiated RCTs; third, to identify risk factors for RCT discontinuation due to insufficient recruitment; fourth, to determine at what stage RCTs are discontinued; and fifth, to examine the publication history of discontinued RCTs. We are currently assembling a multicenter cohort of RCTs based on protocols approved between 2000 and 2002/3 by 6 RECs in Switzerland, Germany, and Canada. We are extracting data on RCT characteristics and planned recruitment for all included protocols. Completion and publication status is determined using information from correspondence between investigators and RECs, publications identified through literature searches, or by contacting the investigators. We will use multivariable regression models to identify risk factors for trial discontinuation due to insufficient recruitment. We aim to include over 1000 RCTs of which an anticipated 150 will have been discontinued due to insufficient recruitment. Discussion Our study will provide insights into the prevalence and characteristics of RCTs that were discontinued. Effective recruitment strategies and the anticipation of problems are key issues in the planning and evaluation of trials
Discontinuous mixed covolume methods for parabolic problems.
Zhu, Ailing; Jiang, Ziwen
2014-01-01
We present the semidiscrete and the backward Euler fully discrete discontinuous mixed covolume schemes for parabolic problems on triangular meshes. We give the error analysis of the discontinuous mixed covolume schemes and obtain optimal order error estimates in discontinuous H(div) and first-order error estimate in L(2).
Institute of Scientific and Technical Information of China (English)
徐宁
2015-01-01
it is universal acknowledgement that grammar takes an indispensable place in English learning yet increasing evidences show that there are still serious problems exists in China grammar teaching:low learning motivation, goal-oriented teaching mode and traditional deductive approach. Freeman’s Three Dimension Theory (1991) suggests that grammar should be understood as three respective:form, meaning, usage. This thesis analyses the dominant deficiencies which reveals traditional teaching mode only lays emphasis on form or meaning. Neglecting on importance of context obscures mastery of grammar rules by students. By the end of this paper, taking teaching of conditionals as examples, a suggestive teaching model is provided based on Three Dimension Theo⁃ry (Freeman, 1991).
Sutherland, Ian; Hewitson, Peter; Ignatova, Svetlana
2009-12-11
Predictable scale-up from test tube derived distribution ratios and analytical-scale sample loading optimisation is demonstrated using a model sample system of benzyl alcohol and p-cresol in a heptane:ethyl acetate:methanol:water phase system with the new 18 L Maxi counter-current chromatography centrifuge. The versatility of having a liquid stationary phase with its high loading capacity and flexible operating modes is demonstrated at two different scales by separating and concentrating target compounds using a mixture of caffeine, vanillin, naringenin and carvone using a quasi-continuous technique called intermittent counter-current extraction.
Directory of Open Access Journals (Sweden)
Anil Kumar Sharma,
2010-08-01
Full Text Available In this paper the current mode approach called “Current Conveyor (CCII+” has been incorporated to design and simulate the circuit for producing two amplitude matched anti-phase sine waveforms which are frequently used in various communication and instrumentation systems. PSpice simulation has been used to depict the output waveforms. The power supply used is ±2.5 V which can be easily incorporated with CMOS IC technology. The designed circuit has been simulated at variousfrequency ranges and the waveforms are obtained after the circuit is optimized.
Aho-Mantila, L.; Potzel, S.; Coster, D. P.; Wischmeier, M.; Brix, M.; Fischer, R.; Marsen, S.; Meigs, A.; Müller, H. W.; Scarabosio, A.; Stamp, M. F.; Brezinsek, S.; the ASDEX Upgrade Team; JET Contributors, the
2017-03-01
The divertor solutions obtained with the plasma edge modelling tool SOLPS5.0 are discussed. The code results are benchmarked against carefully analysed L-mode discharges at various density levels with and without impurity seeding in the full-metal tokamaks ASDEX Upgrade and JET. The role of the cross-field drifts and currents in the solutions is analysed in detail, and the improvements achieved by fully activating the drift and current terms in view of matching the experimental signals are addressed. The persisting discrepancies are also discussed.
Application of Discontinuous PWM Modulation in Active Power Filters
DEFF Research Database (Denmark)
Blaabjerg, Frede; Asiminoaei, Lucian; Rodriguez, Pedro
2008-01-01
Classical discontinuous pulsewidth modulations (DPWMs) may not be efficiently applied in active power filters (APFs), because it is hard to predict the peak values of the inverter current, and consequently it is difficult to calculate the position of the clamped interval, that minimizes the switc...
Integrated on-chip 0.35 μm BiCMOS current-mode DC-DC buck converter
Lee, Chan-Soo; Kim, Nam-Soo; Gendensuren, Munkhsuld; Choi, Jae-Ho; Choi, Joong-Ho
2012-12-01
A current-mode DC-DC buck converter with a fully integrated power module is presented in this article. The converter is implemented using BiCMOS technology in amplifier and power MOSFET in a current sensor. The current sensor is realised by the power lateral double-diffused MOSFET with the aspect ratio much larger than that of a matched p-MOSFET. In addition, BiCMOS technology is applied in the error amplifier for an accurate current sensing and a fast transient response. The DC-DC converter is fabricated with 0.35 µm BiCMOS process. Experimental results show that the fully integrated converter operates at 1.3 MHz switching frequency with a supply voltage of 5 V. The output DC voltage is obtained as expected and the output ripple is controlled to be within 2% with a 30 µH off-chip inductor and 100 µF off-chip capacitor.
Directory of Open Access Journals (Sweden)
Thawatchai Onjun
2012-02-01
Full Text Available The investigation of bootstrap current formation in ITER is carried out using BALDUR integrated predictive modelingcode. The combination of Mixed B/gB anomalous transport model and NLCASS module together with the pedestal model isused in BALDUR code to simulate the time evolution of temperature, density, and plasma current profiles. It was found inthe simulations that without the presence of ITB, a minimal fraction of bootstrap current (as well as low fusion performancewas achieved. The enhancement due to ITB depends sensitively on the strength of toroidal velocity. A sensitivity study wasalso carried out to optimize the bootstrap current fraction and plasma performance. It was found that the bootstrap currentfraction slightly improved; while the plasma performance greatly improved with increasing of NBI power or pedestal temperature.On the other hand, higher impurity concentration resulted in a significant degradation of fusion performance, buta smaller degradation in bootstrap current.
Magnetic and transport properties of discontinuous metal-oxides multilayers
Energy Technology Data Exchange (ETDEWEB)
Dinia, A.; Schmerber, G.; Ulhaq, C.; El Bahraoui, T
2003-02-15
We report on structural, magnetic and transport properties of Al{sub 2}O{sub 3}/CoFe discontinuous multilayers deposited by RF sputtering at room temperature on silicon substrate. Transmission electron microscopy observations show that these multilayers consist of discontinuous layers of CoFe particles embedded in an insulating Al{sub 2}O{sub 3} matrix. This is further supported by magnetization measurements showing the presence at room temperature of both superparamagnetic and ferromagnetic components. The current-in-plane resistivity of the discontinuous multilayers has shown a negative magnetoresistance due to a spin-dependent tunneling between the CoFe magnetic particles through the insulating Al{sub 2}O{sub 3} barrier. The magnetoresistance response gives rise to two spin-dependent tunneling contributions. A contribution at small applied fields due to ferromagnetic particles and a contribution at larger magnetic applied fields due to a superparamagnetic particles.
Current-Mode CMOS A/D Converter for Pico Ampere-Range with a Potentiostatic Input
DEFF Research Database (Denmark)
Breten, Madalina
1999-01-01
amount of a certain gas in a solution, such as oxygen in blood, can be determined by measuring the concentration-dependent current. The circuit that maintains the electrochemical stability in the sensor, as well as buffering the current output is called potentiostat.The DC current at the output....... In this context conversion techniques of the integration-type are preferred, such as dual-slope, multi-slope, or sigma-delta modulation. The performances of the comparator, clock-feedthrough effect, and the offset compensation are the main problems. Furthermore, if an analog circuit is designed as a building......-out. The influence and methods to reduce the nonlinearities of the A/D converter are discussed. At the input of the integrator was implemented a bridge of 4-switches in order to measure the low current with minimum charge injection, and to overcome the drift problems.A new conversion technique is proposed: folded-dual-slope...
A fast novel soft-start circuit for peak current-mode DC—DC buck converters
Jie, Li; Miao, Yang; Weifeng, Sun; Xiaoxia, Lu; Shen, Xu; Shengli, Lu
2013-02-01
A fully integrated soft-start circuit for DC—DC buck converters is presented. The proposed high speed soft-start circuit is made of two sections: an overshoot suppression circuit and an inrush current suppression circuit. The overshoot suppression circuit is presented to control the input of the error amplifier to make output voltage limit increase in steps without using an external capacitor. A variable clock signal is adopted in the inrush current suppression circuit to increase the duty cycle of the system and suppress the inrush current. The DC—DC converter with the proposed soft-start circuit has been fabricated with a standard 0.13 μm CMOS process. Experimental results show that the proposed high speed soft-start circuit has achieved less than 50 μs start-up time. The inductor current and the output voltage increase smoothly over the whole load range.
A fast novel soft-start circuit for peak current-mode DC-DC buck converters
Institute of Scientific and Technical Information of China (English)
Li Jie; Yang Miao; Sun Weifeng; Lu Xiaoxia; Xu Shen; Lu Shengli
2013-01-01
A fully integrated soft-start circuit for DC-DC buck converters is presented.The proposed high speed soft-start circuit is made of two sections:an overshoot suppression circuit and an inrush current suppression circuit.The overshoot suppression circuit is presented to control the input of the error amplifier to make output voltage limit increase in steps without using an external capacitor.A variable clock signal is adopted in the inrush current suppression circuit to increase the duty cycle of the system and suppress the inrush current.The DC-DC converter with the proposed soft-start circuit has been fabricated with a standard 0.13 μm CMOS process.Experimental results show that the proposed high speed soft-start circuit has achieved less than 50 μs start-up time.The inductor current and the output voltage increase smoothly over the whole load range.
Active postoperative acromegaly: sustained remission after discontinuation of somatostatin analogues
Cardenas-Salas, Jersy
2016-01-01
Summary In patients with active acromegaly after pituitary surgery, somatostatin analogues are effective in controlling the disease and can even be curative in some cases. After treatment discontinuation, the likelihood of disease recurrence is high. However, a small subset of patients remains symptom-free after discontinuation, with normalized growth hormone (GH) and insulin-like growth factor (IGF1) levels. The characteristics of patients most likely to achieve sustained remission after treatment discontinuation are not well understood, although limited evidence suggests that sustained remission is more likely in patients with lower GH and IGF1 levels before treatment withdrawal, in those who respond well to low-dose treatment, in those without evidence of adenoma on an MRI scan and/or in patients who receive long-term treatment. In this report, we describe the case of a 56-year-old female patient treated with lanreotide Autogel for 11 years. Treatment was successfully discontinued, and the patient is currently disease-free on all relevant parameters (clinical, biochemical and tumour status). The successful outcome in this case adds to the small body of literature suggesting that some well-selected patients who receive long-term treatment with somatostatin analogues may achieve sustained remission. Learning points: The probability of disease recurrence is high after discontinuation of treatment with somatostatin analogues. Current data indicate that remission after treatment discontinuation may be more likely in patients with low GH and IGF1 levels before treatment withdrawal, in those who respond well to low-dose treatment, in those without evidence of adenoma on MRI, and/or in patients receiving prolonged treatment. This case report suggests that prolonged treatment with somatostatin analogues can be curative in carefully selected patients. PMID:27933171
Continuities, Discontinuities, Interactions: Values, Education, and Neuroethics
Semetsky, Inna
2009-01-01
This article begins by revisiting the current model of values education (moral education) which has recently been set up in Australian schools. This article problematizes the pedagogical model of teaching values in the direct transmission mode from the perspective of the continuity of experience as central to the philosophies of John Dewey and…
CSIR Research Space (South Africa)
Coetzer, A
2016-01-01
Full Text Available The design and implementation of a bidirectional current-controlled voltage-regulated DC-DC converter is presented. The converter is required to connect a battery of electrochemical cells (the battery) to an asynchronous motor-drive unit via a...
Observations of double discontinuities in the magnetotail
Whang, Y. C.; Fairfield, D.; Smith, E. J.; Lepping, R. P.; Kokubun, S.; Saito, Y.
Observations of slow shocks in the Earth's magnetotail at the plasma sheet-lobe boundaries have been well documented. We restudy the magnetic field data of two slow shocks: one was observed from Geotail on January 17, 1994 at XGSE = -92 RE, and another was observed from ISEE-3 on February 2, 1983 at XGSE = -220 RE. In both cases, the slow shock layer was followed by an adjoining rotational discontinuity layer on the postshock side. Compound structures each composed of a slow shock layer and an adjoining rotational discontinuity layer have been recently observed in interplanetary space from Wind, Geotail and Imp-8. Because the two successive discontinuities are very close to each other, the compound structure looks like a new kind of MHD discontinuity. It may be called a double discontinuity. Since double discontinuities exist not only in interplanetary space but also in the magnetotail region, they could be a general MHD structure in space plasma.
Institute of Scientific and Technical Information of China (English)
李小峰; 戴栋; 马西奎
2003-01-01
在不连续运行模式条件下,建立了分析电流反馈型Buck-Boost变换器中的分岔行为和混沌过程的分段离散迭代映射方程,得到了以输入电压E为参数的分岔图和相图.数值结果表明,工作于不连续模式下的电流反馈型Buck-Boost变换器会出现特有的一些非光滑分岔现象.例如,与光滑系统中典型的倍周期分岔不同的是,在周期1到周期2的倍周期分岔点附近,周期2轨道分枝不垂直于周期1轨道分枝,并且直接经周期6到达混沌态.
Constitutive model of discontinuous plastic flow at cryogenic temperatures
Skoczen, B; Bielski, J; Marcinek, D
2010-01-01
FCC metals and alloys are frequently used in cryogenic applications, nearly down to the temperature of absolute zero, because of their excellent physical and mechanical properties including ductility. Some of these materials, often characterized by the low stacking fault energy (LSFE), undergo at low temperatures three distinct phenomena: dynamic strain ageing (DSA), plastic strain induced transformation from the parent phase (gamma) to the secondary phase (alpha) and evolution of micro-damage. The constitutive model presented in the paper is focused on the discontinuous plastic flow (serrated yielding) and takes into account the relevant thermodynamic background. The discontinuous plastic flow reflecting the DSA effect is described by the mechanism of local catastrophic failure of Lomer-Cottrell (LC) locks under the stress fields related to the accumulating edge dislocations (below the transition temperature from the screw dislocations to the edge dislocations mode T-1). The failure of LC locks leads to mass...
Computational aeroacoustics applications based on a discontinuous Galerkin method
Delorme, Philippe; Mazet, Pierre; Peyret, Christophe; Ventribout, Yoan
2005-09-01
CAA simulation requires the calculation of the propagation of acoustic waves with low numerical dissipation and dispersion error, and to take into account complex geometries. To give, at the same time, an answer to both challenges, a Discontinuous Galerkin Method is developed for Computational AeroAcoustics. Euler's linearized equations are solved with the Discontinuous Galerkin Method using flux splitting technics. Boundary conditions are established for rigid wall, non-reflective boundary and imposed values. A first validation, for induct propagation is realized. Then, applications illustrate: the Chu and Kovasznay's decomposition of perturbation inside uniform flow in term of independent acoustic and rotational modes, Kelvin-Helmholtz instability and acoustic diffraction by an air wing. To cite this article: Ph. Delorme et al., C. R. Mecanique 333 (2005).
Discontinuation of oxytocin in the active phase of labor.
Girard, Bénédicte; Vardon, Delphine; Creveuil, Christian; Herlicoviez, Michel; Dreyfus, Michel
2009-01-01
To show that early discontinuation of oxytocin will not increase the mean duration of the active labor phase in a clinically significant way. Controlled non-inferiority study. Department of Obstetrics and Gynecology, University of Caen, Clemenceau Hospital, France. A total of 138 women with singleton pregnancy and a vertex presentation of over 34 gestational weeks, presenting a medical indication of induction of labor or a dystocia at onset of labor, from May 2005 to June 2006. Two parallel groups were compared: continuation of oxytocin until delivery versus discontinuation of oxytocin at the onset of the active phase. The clinically acceptable increase in mean duration of the active phase of labor (non-inferiority margin) was set at 60 minutes. Primary outcome measure was duration of the active labor phase. Secondary outcome measures included total duration of labor, parameters concerning oxytocin use, rates of uterine hyperstimulation and fetal heart rate (FHR) abnormalities, and mode of delivery. Some neonatal outcomes were also analyzed. Equivalence of the two strategies (continuation vs. discontinuation of oxytocin) was not demonstrated (p=0.97 testing for non-inferiority), the active phase even being significantly longer by a mean of 113 minutes (p=0.0001 testing for superiority). The rates of cesarean sections, alterations of FHR and delivery hemorrhage were higher when oxytocin was continued, but not significantly. There were significantly more infants hospitalized in neonatology when oxytocin was continued (p=0.028). Discontinuation of oxytocin at the onset of the active phase prolongs labor. We found no argument for discontinuing the infusion of oxytocin at the onset of the active phase.
A Novel 800mV Reference Current Source Circuit for Low-Power Low-Voltage Mixed-Mode Systems
Kwon, Oh Jun; Kwack, Kae Dal
In this paper, a novel 800mV beta-multiplier reference current source circuit is presented. In order to cope with the narrow input common-mode range of the Opamp in the reference circuit, the resistive voltage divider was employed. High gain Opamp was designed to compensate for the intrinsic low output resistance of the MOS transistors. The proposed reference circuit was designed in a standard 0.18µm CMOS process with nominal Vth of 420mV and -450mV for n-MOS and p-MOS transistor, respectively. The total power consumption including Opamp is less than 50µW.
Spatially discontinuous ionization phenomenon in inhomogeneous soil
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
By using X-ray film imaging technology,a phenomenon of discontinuous ionization was observed in the inhomogeneous soil around the grounding electrode on which a surge voltage was applied.A simplified two-phase solid-gas model was built to study the electric field distribution in the soil to explain the discontinuous ionization phenomenon.Analysis showed the differences of the dielectric properties,the shapes and sizes of soil particles can cause discontinuous ionization in the soil.
Vanga, Subba R; Satti, Sudhakar R; Williams, James; Weintraub, William; Doorey, Andrew
2015-01-01
Oral anticoagulants (OAC) are the therapy of choice to prevent thromboembolism in patients at risk. Discontinuation of OAC prior to elective medical and surgical procedures may reduce the risk of bleeding, but may expose patients to increased risk of thromboembolism and ischemic stroke. The current public health burden of ischemic strokes associated with OAC discontinuation is unknown. We aimed to study the prevalence OAC discontinuation in patients who presented with acute ischemic stroke as well as the outcomes of these strokes. Retrospective cross-sectional study by intensive chart review of all acute ischemic stroke patients over 6 months in a large tertiary care community hospital. A total of 431 patients with acute ischemic stroke were admitted during study period, of which 11 (2.6%) had OAC discontinuation within 120 days prior to the index admission. Several strokes occurred after relatively brief discontinuations. The patient group with discontinuation was older, had higher comorbidities and also had a clinically significant stroke and resulting higher mortality and morbidity. About 2.6% or 1 in every 38 of all ischemic stokes occurred after OAC discontinuation. Strokes occurring after OAC discontinuation also have higher mortality and morbidity. Our data suggest that any planned discontinuation of OAC, however brief, should be carefully considered.
2010-01-01
International audience; UV excimer lamps are efﬁcient narrowband sources of UV radiation with applications in various domains. The issue of controlling the UV emission by means of the power supply associated with such lamps favors pulsed current-controlled generators. After having established the previous statements, we propose a dedicated power converter topology which implements the needed performances. The analysis of the degrees of freedom of this structure shows the capability of this pu...
Dynamics of the electric current in an ideal electron gas: a sound mode inside the quasi-particles
Grozdanov, Sašo
2015-01-01
We study the equation of motion for the Noether current in an electron gas within the framework of the Schwinger-Keldysh Closed-Time-Path formalism. The equation is shown to be highly non-linear and irreversible even for a non-interacting, ideal gas of electrons at non-zero density. We truncate the linearised equation of motion, written as the Laurent series in Fourier space, so that the resulting expressions are local in time, both at zero and at small finite temperatures. Furthermore, we show that the one-loop Coulomb interactions only alter the physical picture quantitatively, while preserving the characteristics of the dynamics that the electric current exhibits in the absence of interactions. As a result of the composite nature of the Noether current, composite sound waves are found to be the dominant IR collective excitations at length scales between the inverse Fermi momentum and the mean free path that would exist in an interacting electron gas. We also discuss the difference and the transition betwee...
The performance of proper orthogonal decomposition in discontinuous flows
Directory of Open Access Journals (Sweden)
Jing Li
2016-09-01
Full Text Available In this paper, flow reconstruction accuracy and flow prediction capability of discontinuous transonic flow field by means of proper orthogonal decomposition (POD method is studied. Although linear superposition of “high frequency waves” in different POD modes can achieve the reconstruction of the shock wave, the smoothness of the solution near the shock wave cannot be guaranteed. The modal coefficients are interpolated or extrapolated and different modal components are superposed to realize the prediction of the flow field beyond the snapshot sets. Results show that compared with the subsonic flow, the transonic flow with shock wave requires more POD modes to reach a comparative reconstruction accuracy. When a shock wave exists, the interpolation prediction ability is acceptable. However, large errors exist in extrapolation, and increasing the number of POD modes cannot effectively improve the prediction accuracy of the flow field.
Sai, Toru; Sugimoto, Yasuhiro
By using a quadratic compensation slope, a CMOS current-mode buck DC-DC converter with constant frequency characteristics over wide input and output voltage ranges has been developed. The use of a quadratic slope instead of a conventional linear slope makes both the damping factor in the transfer function and the frequency bandwidth of the current feedback loop independent of the converter's output voltage settings. When the coefficient of the quadratic slope is chosen to be dependent on the input voltage settings, the damping factor in the transfer function and the frequency bandwidth of the current feedback loop both become independent of the input voltage settings. Thus, both the input and output voltage dependences in the current feedback loop are eliminated, the frequency characteristics become constant, and the frequency bandwidth is maximized. To verify the effectiveness of a quadratic compensation slope with a coefficient that is dependent on the input voltage in a buck DC-DC converter, we fabricated a test chip using a 0.18µm high-voltage CMOS process. The evaluation results show that the frequency characteristics of both the total feedback loop and the current feedback loop are constant even when the input and output voltages are changed from 2.5V to 7V and from 0.5V to 5.6V, respectively, using a 3MHz clock.
CMOS Analog Multiplier Based on Current Mode Subtitle as Needed%基于电流模电路的CMOS模拟乘法器设计
Institute of Scientific and Technical Information of China (English)
王永杰; 郭强
2012-01-01
以基本电流模电路为基础,分别对两种常用工艺,即双极性和CMOS工艺的电流平方电路进行了分析.它们分别由跨导线性环和电流镜基本电路构成.主要对CMOS器件构成的电流平方电路进行了设计与分析.最后设计了一种以MOS电流平方电路为主要模块的乘法器电路,实现了电流信号的相乘运算,并通过仿真验证了结果的正确性.%On the basic current mode circuit, current squaring circuit of translinear loop and mirror current source is analysed. Above two circuit is respectively connected with BJT and MOS technology. Finally, designed multiplier circuit based on MOS current square circuit, implemented the multiplication of current signals.
Institute of Scientific and Technical Information of China (English)
Li Shutao; Wang Yaonan; Wu Jie
2001-01-01
In this paper a novel log-domain current-mode integrator based on MOS transistors in subthreshold is proposed. The integrator's time-constant is tunable by varying a reference bias current. By use of the integrator, a fifth-order Chebyshev lowpass filter with 0.1dB ripples is designed. The simulation results demonstrate that the proposed filter has such advantages as low power supply(1.5V), very low power dissipation (μW level), nearly ideal frequency response, very small sensitivity to components in passband, and adjustable cut-off frequency over a wide range.The circuit is composed of NMOS transistors and grounded capacitors which make it suitable for fully integrated circuit implementation.
Directory of Open Access Journals (Sweden)
A. Lahiri
2011-09-01
Full Text Available This paper proposes a new, compact CMOS realization of current-mode (CM first-order all-pass filter (APF using no external resistors. The circuit is created using only ten transistors and one external capacitor. The circuit uses lower number of transistors as compared to previously reported CM APFs using active building block (ABB based approach. A comparison with previously reported CM APFs in terms of number of transistors and current consumption has been provided. As a design example, a 512 kHz pole-frequency (at typical process and 27ºC CM APF is designed in 40nm CMOS technology and validated through SPICE simulations.
Gao, Yonghao; Yerokhin, Aleksey; Matthews, Allan
2014-10-01
Plasma electrolytic oxidation (PEO) coatings were produced on commercially pure magnesium in a biologically friendly electrolyte composed of 2 g L-1 Ca(OH)2 and 12 g L-1 Na3PO4·12H2O using pulsed unipolar and bipolar current regimes with negative biasing varying from 0 to 20 mA cm-2. Analysis of voltage transients was performed to characterise the PEO processes. The coating morphology and phase composition were studied by scanning electron microscopy and X-ray diffraction technique, respectively. In vitro corrosion performance of the coatings was evaluated in a simulated body fluid at 37 ± 1 °C, using electrochemical techniques including open circuit potential monitoring, electrochemical impedance spectroscopy and potentiodynamic polarisation scans. The influence of the negative biasing on the PEO process and resulting coating characteristics is discussed. Unlike generally recognised beneficial effects of the negative biasing in PEO treatments of some other metal-electrolyte systems, it was found that detrimental effects are induced to the coatings on cp-Mg produced in the studied electrolyte when the negative current amplitude increases, which may be attributed to hydrogen liberation at the coating/substrate interface during the negative biasing cycles. As a result, a deterioration of vitro corrosion performance was observed for the pulsed bipolar PEO coatings compared to those produced using the pulsed unipolar regime which provides better quality coatings.
Directory of Open Access Journals (Sweden)
B. I. Firago
2006-01-01
Full Text Available The influence of modem firequency converters with uncontrolled rectifiers on the supply network is investigated in this paper. The developed mathematical model permits us to analyze rectifier input currents with symmetrical and asymmetrical supply networks and in discontinuous operational mode. Results of modeling in case of asymmetrical supply network are shown in the form of mains current curves and current spectrum of one phase.
Generalized Modal Analysis of Electromagnetic - and Quantum-Waveguide Structures and Discontinuities
Weisshaar, Andreas
Generalized modal analysis techniques for the characterization and modeling of dissipationless planar waveguide structures and discontinuities encountered in microwave and optical integrated circuits, as well as of quantum waveguide structures and devices, are presented. The frequency-dependent transmission properties of the curved microstrip bend are derived by utilizing a second-order perturbation analysis of the equivalent modified curved waveguide model and a mode-matching method which includes the higher order modes. An extension of the mode-matching method for characterization of microstrip right-angle bends and T junctions having a rectangular notch is formulated. The modal solutions for an arbitrary graded-index dielectric slab waveguide are derived by applying the generalized telegraphist's equations to the equivalent inhomogeneous parallel-plate waveguide model with electric or magnetic walls. These modal solutions are employed in a mode-matching procedure to calculate the transmission properties of a step discontinuity in typical diffused optical dielectric slab waveguides. Power loss calculations for an abrupt offset in a diffused optical waveguide show a smooth increase in radiation loss whereas a sharp transition from almost zero to nearly total radiation loss is found for an abrupt change in diffusion depth. In the analysis of quantum waveguide structures, the modal expansions of the wave function together with a mode-matching technique are utilized. The computed generalized scattering matrices (GSMs) of junctions and uniform waveguide sections are combined via an extended GSM technique to obtain the scattering parameters of composite quantum waveguide structures. Results for cascaded right-angle bends and periodic multi-waveguide structures in a split-gate configuration are presented assuming hard wall confinement. For the multisection structures, strong resonant behavior similar to that in resonant tunneling diodes is found. Calculated current
Directory of Open Access Journals (Sweden)
A. A. Lubchich
2005-07-01
Full Text Available Characteristics of small amplitude plane waves within the medium separated by the plane discontinuity into two half spaces are analysed. The approximation of the ideal one-fluid magnetohydrodynamics (MHD is used. The discontinuities with the nonzero mass flux across them are mainly examined. These are fast or slow shock waves and rotational discontinuities. The dispersion equation for MHD waves within each of half space is obtained in the reference frame connected with the discontinuity surface. The solution of this equation permits one to determine the wave vectors versus the parameter c_{p}, which is the phase velocity of surface discontinuity oscillations. This value of c_{p} is common for all MHD waves and determined by an incident wave or by spontaneous oscillations of the discontinuity surface. The main purpose of the study is a detailed analysis of the dispersion equation solution. This analysis let us draw the following conclusions. (I For a given c_{p}, ahead or behind a discontinuity at most, one diverging wave can transform to a surface wave damping when moving away from the discontinuity. The surface wave can be a fast one or, in rare cases, a slow, magnetoacoustic one. The entropy and Alfvén waves always remain in a usual homogeneous mode. (II For certain values of c_{p} and parameters of the discontinuity behind the front of the fast shock wave, there can be four slow magnetoacoustic waves, satisfying the dispersion equation, and none of the fast magnetoacoustic waves. In this case, one of the four slow magnetoacoustic waves is incident on the fast shock wave from the side of a compressed medium. It is shown that its existence does not contradict the conditions of the evolutionarity of MHD shock waves. The four slow magnetoacoustic waves, satisfying the dispersion equation, can also exist from either side of a slow shock wave or rotational discontinuity. (III The
Discontinuities during UV writing of waveguides
DEFF Research Database (Denmark)
Svalgaard, Mikael; Harpøth, Anders; Andersen, Marc
2005-01-01
UV writing of waveguides can be hampered by discontinuities where the index change process suddenly shuts down. We show that thermal effects may account for this behaviour.......UV writing of waveguides can be hampered by discontinuities where the index change process suddenly shuts down. We show that thermal effects may account for this behaviour....
A generalized discrete strong discontinuity approach
Dias-da-Costa, D.; Alfaiate, J.; Sluys, L.J.; Julio, E.
2010-01-01
Several local embedded discontinuity formulations have already been developed, in which constant strain triangles and constant jumps are adopted. However, these formulations lead to jump and traction discontinuity across element boundaries and stress locking effects. Herein, a new contribution to em
Directory of Open Access Journals (Sweden)
R. Huang
2015-01-01
Full Text Available We report on measurements and analysis of a field-emitted electron current in the very-high-frequency (VHF gun, a room temperature rf gun operating at high field and continuous wave (CW mode at the Lawrence Berkeley National Laboratory (LBNL. The VHF gun is the core of the Advanced Photo-injector Experiment (APEX at LBNL, geared toward the development of an injector for driving the next generation of high average power x-ray free electron lasers. High accelerating fields at the cathode are necessary for the high-brightness performance of an electron gun. When coupled with CW operation, such fields can generate a significant amount of field-emitted electrons that can be transported downstream the accelerator forming the so-called “dark current.” Elevated levels of a dark current can cause radiation damage, increase the heat load in the downstream cryogenic systems, and ultimately limit the overall performance and reliability of the facility. We performed systematic measurements that allowed us to characterize the field emission from the VHF gun, determine the location of the main emitters, and define an effective strategy to reduce and control the level of dark current at APEX. Furthermore, the energy spectra of isolated sources have been measured. A simple model for energy data analysis was developed that allows one to extract information on the emitter from a single energy distribution measurement.
Active postoperative acromegaly: sustained remission after discontinuation of somatostatin analogues
Directory of Open Access Journals (Sweden)
Cristina Alvarez-Escola
2016-11-01
Full Text Available In patients with active acromegaly after pituitary surgery, somatostatin analogues are effective in controlling the disease and can even be curative in some cases. After treatment discontinuation, the likelihood of disease recurrence is high. However, a small subset of patients remains symptom-free after discontinuation, with normalized growth hormone (GH and insulin-like growth factor (IGF1 levels. The characteristics of patients most likely to achieve sustained remission after treatment discontinuation are not well understood, although limited evidence suggests that sustained remission is more likely in patients with lower GH and IGF1 levels before treatment withdrawal, in those who respond well to low-dose treatment, in those without evidence of adenoma on an MRI scan and/or in patients who receive long-term treatment. In this report, we describe the case of a 56-year-old female patient treated with lanreotide Autogel for 11 years. Treatment was successfully discontinued, and the patient is currently disease-free on all relevant parameters (clinical, biochemical and tumour status. The successful outcome in this case adds to the small body of literature suggesting that some well-selected patients who receive long-term treatment with somatostatin analogues may achieve sustained remission.
A Streaming Language Implementation of the Discontinuous Galerkin Method
Barth, Timothy; Knight, Timothy
2005-01-01
We present a Brook streaming language implementation of the 3-D discontinuous Galerkin method for compressible fluid flow on tetrahedral meshes. Efficient implementation of the discontinuous Galerkin method using the streaming model of computation introduces several algorithmic design challenges. Using a cycle-accurate simulator, performance characteristics have been obtained for the Stanford Merrimac stream processor. The current Merrimac design achieves 128 Gflops per chip and the desktop board is populated with 16 chips yielding a peak performance of 2 Teraflops. Total parts cost for the desktop board is less than $20K. Current cycle-accurate simulations for discretizations of the 3-D compressible flow equations yield approximately 40-50% of the peak performance of the Merrimac streaming processor chip. Ongoing work includes the assessment of the performance of the same algorithm on the 2 Teraflop desktop board with a target goal of achieving 1 Teraflop performance.
Periodic Orbits in a Second-Order Discontinuous System with an Elliptic Boundary
Li, Liping; Luo, Albert C. J.
2016-12-01
This paper develops the analytical conditions for the onset and disappearance of motion passability and sliding along an elliptic boundary in a second-order discontinuous system. A periodically forced system, described by two different linear subsystems, is considered mainly to demonstrate the methodology. The passable, sliding and grazing conditions of a flow to the elliptic boundary in the discontinuous dynamical system are provided through the analysis of the corresponding vector fields and G-functions. Moreover, by constructing appropriate generic mappings, periodic orbits in such a discontinuous system are predicted analytically. Finally, three different cases are discussed to illustrate the existence of periodic orbits with passable and/or sliding flows. The results obtained in this paper can be applied to the sliding mode control in discontinuous dynamical systems.
Oxytocin discontinuation after the active phase of labor is established.
Vlachos, Dimitrios-Efthymios G; Pergialiotis, Vasilios; Papantoniou, Nikolaos; Trompoukis, Stamoulis; Vlachos, Georgios D
2015-08-01
Despite the widespread usage of oxytocin, there is still no consensus on its mode of administration. The scope of the present meta-analysis was to assess the effect of oxytocin discontinuation after the active phase of labor is established on maternal fetal and neonatal outcomes. We searched Medline, Scopus, Popline, ClinicalTrials.gov and Google Scholar databases. Eight studies were finally retrieved, which involved 1232 parturient. We observed significantly decreased rates of cesarean sections among parturient that discontinued oxytocin (OR 0.51, 95% CI 0.35, 0.74) as well as decreased rates of uterine hyperstimulation (OR 0.33, 95% CI 0.19, 0.58). Similarly, cases of non-reassuring fetal heart rates were fewer among women that did not receive oxytocin after the establishment of the active phase of labor (OR 0.63, 95% CI 0.41, 0.97). Keeping in mind the aforementioned maternal and neonatal adverse effects that seem to result from infusion of oxytocin until delivery, future practice should aim towards its discontinuation after the establishment of the active phase of labor, as it does not seem to influence the total duration of labor. Future studies should aim towards specific populations of parturient in order to clarify whether different approaches are needed.
DEFF Research Database (Denmark)
Xu, G.S.; Wan, B.N.; Li, J.G.
2011-01-01
The first high-confinement mode (H-mode) with type-III edge localized modes at an H factor of HIPB98(y,2) ~ 1 has been obtained with about 1 MW lower hybrid wave power on the EAST superconducting tokamak. The first H-mode plasma appeared after wall conditioning by lithium (Li) evaporation before ...
Institute of Scientific and Technical Information of China (English)
沙金; 包伯成; 许建平; 高玉
2012-01-01
According to the charge variation of output capacitor in a switching cycle, the output voltage variation in a switching cycle can be obtained, from which an approximate discrete-time model of pulse train （PT） controlled buck converter operating in discontinuous conduction mode （DCM） is established. Based on the model, the border-collision bifurcations of the PT controlled DCM buck converter with the variations of the load resistance and the input voltage are studied. By constructing the corresponding iterative map curves, the stabilities of the fixed points, formed by the orbits of period-l, period-2, period-3 and so on, are analyzed, and the mechanisms of border-collision bifurcations of the converter under different operation states are revealed. The analysis results indicate that with the variation of parameters, the PT controlled DCM buck converter always operates in different periodic states, in which the change of the operation mode with periodic state is caused by the border-collision bifurcation and the lyapunov exponent is always less than zero. By using PSIM circuit simulation software, the time domain waveforms and phase portraits under different load resistances are obtained. Experimental results are provided to verify the correctnesses of theoretical analyses and circuit simulations and the feasibility of dynamical modelling.%通过建立一个开关周期内输出电容电荷变化量对应的输出电压变化量，建立了工作于电感电流断续模式（discontinuousconductionmode，DCM）的脉冲序列（pulsetrain，VT）控制Buck变换器的近似离散时间模型，研究了负载电阻及输入电压变化时PT控制DCMBuck变换器的边界碰撞分岔行为．通过构造相应的迭代映射曲线，分别分析了不同负载电阻时阿控制DCMBuck变换器的周期1、周期2和周期3运行轨迹的不动点稳定性，揭示了PT控制DCMBuck变换器在不同周期态时的边界碰撞分岔的形成机理．研究结
Liu, Qi; Zeng, Hualiang; Jiang, Shujing; Zhang, Li; Yang, Fuzhu; Chen, Xiaoqing; Yang, Hua
2015-11-01
In this study, off-line two-dimensional High Speed Counter-Current Chromatography (2D HSCCC) strategy combined with recycling elution mode was developed to isolate compounds from the ethyl acetate extract of a common green tea--leaves of Malus hupehensis (Pamp.) Rehder. In the orthogonal separation system, a conventional HSCCC was employed for the first dimension and two recycling HSCCCs were used for the second in parallel. Using a solvent system consisting of n-hexane-ethyl acetate-methanol-water (1:4:0.6:4.4, v/v) in the first and second dimension, four compounds including 3-hydroxy-phlorizin (1), phloretin (2), avicularin (3) and kaempferol 3-O-β-D-glucoside (4) were obtained. The purities of these four compounds were all over 95.0% as determined by HPLC. And their structures were all identified through UV, MS and (1)H NMR. It has been demonstrated that the combination of off-line 2D HSCCC with recycling elution mode is an efficient technique to isolate compounds with similar polarities in natural products.
Islam, Rokibul; Pedrow, Patrick; Lekobou, William; Englund, Karl
2013-09-01
A broad band current sensor is being used to monitor the various phenomena (primary streamers, secondary streamers, back corona, etc.) associated with an atmospheric pressure needle-array-to-grounded-screen corona discharge. The reactor consists of a PVC tube and the needle array consists of nickel coated steel electrodes with radius of curvature about 50 μ . The grounded screen is made from stainless steel mesh and applied voltage has a frequency of 60 Hz with an RMS value ranging from 0 to 10 kV. The voltage sensor is a resistive divider and the current sensor is a viewing resistor with value 50 Ω. The feed gas stream is presently (argon + acetylene) or (argon + oxygen) with the argon acting as carrier gas and the acetylene and oxygen acting as precursor gases. Voltage and current are captured with a LeCroy 9350AL 500MHz oscilloscope and analyzed with Matlab using digital signal processing algorithms. The goals of the research are 1) to measure reactor electrical power on a real time basis; 2) to provide real time control of the applied voltage and thus avoid spark conditions; and 3) to identify the various corona modes present in the reactor. Processing of substrates takes place downstream from the grounded screen, outside of the harsh corona discharge environment.
Institute of Scientific and Technical Information of China (English)
李永安; 樊战亭; 吉军
2009-01-01
以传统的双调谐带通滤波器为原型,先利用CCCⅡ设计出V-I变换器、模拟电阻、接地和浮地模拟电感,再用这些基本电路模块分别代替滤波器原型中的端接电阻、接地和浮地电感等,从而设计出了电控双调谐四阶电流模式带通滤波器.讨论了弱耦合、强耦合和临界耦合三种现象.在临界耦合条件下,滤波器的中心频率为10.916 080 MHz,3 dB带宽为2.828 MHz.电路的参数可电控调谐,所有电容接地,没有无源电阻,因而适宜集成.计算机仿真与理论分析一致.%On the basis of traditional band-pass filter with coupled tunability,the basic cercuit modes of a V-I coverter,a analog resistor,a earthed and a floating-earthed analog inductance were all given by CCCⅡ.The terminal resistor,the earthed and the floating-earthed inductance etc in the prototype of filter were substituted by the basic circuit modes.Forth-order current-mode band-pass filter with coupled tunability by current using CCCⅡ was realized,and weak coupling,strong coupling and critical coupling were discussed.The center frequency of the filter is 10.916 080 MHz and the 3 dB bandwidth is 2.828 MHz under critical coupling.The circuit parameters can be tuned by external bias current of CCCⅡ,and capacitors are all earthed,there is no passive resistor,which make it suitable for VLSI technology.Computer simulating results are consistent with theoretical analysis.
Ranatunga, Vipul; Bednarcyk, Brett A.; Arnold, Steven M.
2010-01-01
A method for performing progressive damage modeling in composite materials and structures based on continuum level interfacial displacement discontinuities is presented. The proposed method enables the exponential evolution of the interfacial compliance, resulting in unloading of the tractions at the interface after delamination or failure occurs. In this paper, the proposed continuum displacement discontinuity model has been used to simulate failure within both isotropic and orthotropic materials efficiently and to explore the possibility of predicting the crack path, therein. Simulation results obtained from Mode-I and Mode-II fracture compare the proposed approach with the cohesive element approach and Virtual Crack Closure Techniques (VCCT) available within the ABAQUS (ABAQUS, Inc.) finite element software. Furthermore, an eccentrically loaded 3-point bend test has been simulated with the displacement discontinuity model, and the resulting crack path prediction has been compared with a prediction based on the extended finite element model (XFEM) approach.
Forecasting Technological Discontinuities in the ICT Industry
DEFF Research Database (Denmark)
Hoisl, Karin; Stelzer, Tobias; Biala, Stefanie
2015-01-01
Building on the existing literature on evolutionary innovation and technological change, this paper aims to identify potential signals of technological discontinuities and to obtain assessments of experts to what extent these signals help them to predict discontinuities. Furthermore, we analyze...... in the ICT industry. The conjoint approach allows for a simulation of the forecasting process and considers utility trade-offs. The results show that for both types of experts the perceived benefit of users most highly contributes to predicting technological discontinuities. Internal experts assign more...... insights to the literature on R&D and innovation management....
Monolithic single mode interband cascade lasers with wide wavelength tunability
von Edlinger, M.; Weih, R.; Scheuermann, J.; Nähle, L.; Fischer, M.; Koeth, J.; Kamp, M.; Höfling, S.
2016-11-01
Monolithic two-section interband cascade lasers offering a wide wavelength tunability in the wavelength range around 3.7 μm are presented. Stable single mode emission in several wavelength channels was realized using the concept of binary superimposed gratings and two-segment Vernier-tuning. The wavelength selective elements in the two segments were based on specially designed lateral metal grating structures defined by electron beam lithography. A dual-step dry etch process provided electrical separation between the segments. Individual current control of the segments allowed wavelength channel selection as well as continuous wavelength tuning within channels. A discontinuous tuning range extending over 158 nm in up to six discrete wavelength channels was achieved. Mode hop free wavelength tuning up to 14 nm was observed within one channel. The devices can be operated in continuous wave mode up to 30 °C with the output powers of 3.5 mW around room temperature.
Barton, Justin E.; Boyer, Mark D.; Shi, Wenyu; Schuster, Eugenio; Luce, Tim C.; Ferron, John R.; Walker, Michael L.; Humphreys, David A.; Penaflor, Ben G.; Johnson, Robert D.
2012-12-01
In order for ITER to be capable of operating in advanced tokamak operating regimes, characterized by a high fusion gain, good plasma confinement, magnetohydrodynamic stability and a non-inductively driven plasma current, for extended periods of time, several challenging plasma control problems still need to be solved. Setting up a suitable toroidal current density profile in the tokamak is key for one possible advanced operating scenario characterized by non-inductive sustainment of the plasma current. At the DIII-D tokamak, the goal is to create the desired current profile during the ramp-up and early flat-top phases of the plasma discharge and then actively maintain this target profile for the remainder of the discharge. The evolution in time of the toroidal current profile in tokamaks is related to the evolution of the poloidal magnetic flux profile, which is modelled in normalized cylindrical coordinates using a first-principles, nonlinear, dynamic partial differential equation (PDE) referred to as the magnetic diffusion equation. The magnetic diffusion equation is combined with empirical correlations developed from physical observations and experimental data from DIII-D for the electron temperature, the plasma resistivity and the non-inductive current drive to develop a simplified, control-oriented, nonlinear, dynamic PDE model of the poloidal flux profile evolution valid for low confinement mode discharges. In this work, we synthesize a robust feedback controller to reject disturbances and track a desired reference trajectory of the poloidal magnetic flux gradient profile by employing the control-oriented model of the system. A singular value decomposition of the static gain matrix of the plant model is utilized to identify the most relevant control channels and is combined with the dynamic response of system around a given operating trajectory to design the feedback controller. A general framework for real-time feedforward + feedback control of magnetic and
Discontinuation of Preventive Drugs in General Practice
DEFF Research Database (Denmark)
Andersen, John Sahl; Lindberg, Laura Maria Glahder; Nixon, Michael Simon
the most preventive drugs are prescribed in general practice. Special considerations exist in relation to medication of elderly patients. The prevalence of polypharmacy and the subsequent increased risk of side effects and drug interactions is high. Drug-related problems represent the fifth leading cause...... of death in the United States. The public expenses to drug treatment are constantly increasing. The possibility to withdraw the medication must be taken into account but the decision to discontinue drugs is complex and poorly understood. Planned studies: 1. Patients’ views upon discontinuation...... of preventive drugs. Qualitative interviews with patients experiencing discontinuation of preventive drugs addressing: Which attitudes do the patients have towards preventive drugs? Which thoughts do the patients have in relation to discontinuation of the drugs? How do they understand their own and the GP...
Beam Coupling Impedances of Small Discontinuities
Kurennoy, S S
2000-01-01
A general derivation of the beam coupling impedances produced by small discontinuities on the wall of the vacuum chamber of an accelerator is reviewed. A collection of analytical formulas for the impedances of small obstacles is presented.
Discontinuous Galerkin for the Radiative Transport Equation
Guermond, Jean-Luc
2013-10-11
This note presents some recent results regarding the approximation of the linear radiative transfer equation using discontinuous Galerkin methods. The locking effect occurring in the diffusion limit with the upwind numerical flux is investigated and a correction technique is proposed.
Conforming finite elements with embedded strong discontinuities
Dias-da-Costa, D.; Alfaiate, J.; Sluys, L.J.; Areias, P.; Fernandes, C.; Julio, E.
2012-01-01
The possibility of embedding strong discontinuities into finite elements allowed the simulation of different problems, namely, brickwork masonry fracture, dynamic fracture, failure in finite strain problems and simulation of reinforcement concrete members. However, despite the significant contributi
Improved Edge Awareness in Discontinuity Preserving Smoothing
Heinrich, Stuart B
2011-01-01
Discontinuity preserving smoothing is a fundamentally important procedure that is useful in a wide variety of image processing contexts. It is directly useful for noise reduction, and frequently used as an intermediate step in higher level algorithms. For example, it can be particularly useful in edge detection and segmentation. Three well known algorithms for discontinuity preserving smoothing are nonlinear anisotropic diffusion, bilateral filtering, and mean shift filtering. Although slight differences make them each better suited to different tasks, all are designed to preserve discontinuities while smoothing. However, none of them satisfy this goal perfectly: they each have exception cases in which smoothing may occur across hard edges. The principal contribution of this paper is the identification of a property we call edge awareness that should be satisfied by any discontinuity preserving smoothing algorithm. This constraint can be incorporated into existing algorithms to improve quality, and usually ha...
Neural networks with discontinuous/impact activations
Akhmet, Marat
2014-01-01
This book presents as its main subject new models in mathematical neuroscience. A wide range of neural networks models with discontinuities are discussed, including impulsive differential equations, differential equations with piecewise constant arguments, and models of mixed type. These models involve discontinuities, which are natural because huge velocities and short distances are usually observed in devices modeling the networks. A discussion of the models, appropriate for the proposed applications, is also provided. This book also: Explores questions related to the biological underpinning for models of neural networks\\ Considers neural networks modeling using differential equations with impulsive and piecewise constant argument discontinuities Provides all necessary mathematical basics for application to the theory of neural networks Neural Networks with Discontinuous/Impact Activations is an ideal book for researchers and professionals in the field of engineering mathematics that have an interest in app...
Discontinuance of ADHD Treatment in Adolescents
Directory of Open Access Journals (Sweden)
J Gordon Millichap
2009-04-01
Full Text Available Prevalence of ADHD drug discontinuance in adolescents and young adults was studied in the UK by using the General Practice Database for patients aged 15-21 years from 1999 to 2006.
Directory of Open Access Journals (Sweden)
Rafał Długosz
2007-01-01
Full Text Available A novel 8-bit current mode interleaved successive approximation (SAR analog-digital converter (ADC has been proposed. The proposed converter architecture is very flexible. Using two control DC voltages and one reference current, the converter can be tuned to work with different sampling rates, number of bits of resolution, and power consumption levels. Due to its very low-power consumption and flexibility, the converter is particularly suitable for application in wireless sensor networks. Compared to other solutions presented in the literature, the proposed converter achieves very high figure of merit (FOM value due to numerous low-power circuit innovations utilized in its design. The circuit has been implemented in CMOS 0.18 μm technology. Minimum energy consumption has been found to be in a 25–250 kS/s range (for clock sampling frequency in a 200 kHz--2 MHz range for a single SAR section with the corresponding power dissipation varying from 220 nW to 560 nW for 0.55 V power supply.
On stochastic and discontinuous optimization methods
Energy Technology Data Exchange (ETDEWEB)
Ermoliev, Y.
1994-12-31
The talk is based on a joint article by Y. Ermoliev, V. Norkin and R. Wets. A new notion of subgradient is introduced which allows to develop easily implementable procedures of discontinuous optimization, in particular, finite-difference approximation schemes. The approach relies on the notion of differentiability in the sense of distributions converting a discontinuous optimization problem into a problem of the stochastic optimization. Applications involving risks and abrupt transitions are discussed.
Variations of Hales Discontinuity beneath South India
Goyal, Ayush; Kosre, Goukaran Kumar; Borah, Kajaljyoti
2016-04-01
Thermodynamic studies show the spinel-garnet transition in fertile and hot mantle should be relatively narrow and should show up in the seismological studies as a discontinuity. The evidence for a shallow lithospheric mantle discontinuity was first proposed by Hales (1969) based on seismological travel time measurement from the Early Rise experiment in the Central United States, where a ~4% increase in the S-wave velocity at a depth of 75 km was observed. The recent studies show, in cratonic blocks with colder geotherms, that it appears at greater depths and over broader intervals, that is, from the Moho to 150 km depth. Different studies interpreted that Hales discontinuity may be due to seismic anisotropy or pervasive partial melts or cation ordering in mantle olivine. In the present study an attempt is made to model the Hales discontinuity in the South Indian shield, by jointly inverting group velocity dispersion and receiver functions, calculated from teleseismic earthquakes recorded at 20 broadband seismograph locations in the study region. South Indian shield is an amalgamation of several crustal blocks, namely, Eastern Dharwar Craton (EDC), Western Dharwar Craton (WDC), Southern Granulite Terrain (SGT) etc. Inversion modeling results show deeper Hales discontinuity (~104-110 km depth) in the south of WDC and SGT, while in the north of Western Dharwar Craton and Eastern Dharwar Craton it varies from ~70-80 km. It is also observed that the Hales Discontinuity is present at greater depth in the western part of Dharwar Craton, compared to the eastern part. Details of the depth, thickness, and the cause of the Hales discontinuity are also investigated. Keywords: Hales Discontinuity, South Indian Shield, Receiver Function, Craton, Inversion modeling.
Discontinuities of multi-Regge amplitudes
Fadin, V S
2014-01-01
In the BFKL approach, discontinuities of multiple production amplitudes in invariant masses of produced particles are discussed. It turns out that they are in evident contradiction with the BDS ansatz for $n$-gluon amplitudes in the planar $N$=4 SYM at $n\\ge 6$. An explicit expression for the NLO discontinuity of the two-to-four amplitude in the invariant mass of two produced gluons is is presented.
Directory of Open Access Journals (Sweden)
Boonyarit Chatthong
2014-06-01
Full Text Available Two different approaches for predicting plasma toroidal velocity (v are developed and used in self-consistent simulations of H-mode plasmas with the presence of ITB using BALDUR integrated predictive modelling code. In the first approach, the toroidal velocity depends on the plasma current density; while in the second approach the toroidal velocity is directly proportional to the ion temperature. The profile of v is used to calculate the ExB flow shear which is a main mechanism for plasma transport suppression, leading to the ITB formation. In all simulations, the core transport model is a combination of NCLASS neoclassical transport and semi-empirical Mixed Bohm/gyro-Bohm model that includes the ITB effects. The boundary condition is set at top of the pedestal and is estimated using a pedestal model based on a combination of magnetic and flow shear stabilization pedestal width scaling and an infinite-n ballooning pressure gradient. Two toroidal velocity models are used to simulate the time evolution of plasma temperature and density profiles of 10 JET discharges. The root mean square error (RMSE is used to compare simulation results of those 10 JET discharges with experimental data. It is found that RMSE of Ti , Te , ne are 28.1%, 31.8%, and 15.0% for the first toroidal velocity model and 25.5%, 30.2%, and 15.1% for the second toroidal velocity model, respectively. Furthermore, this suite of codes is used to predict the ITER performance under standard type I ELMy H-mode. It is found that the simulation yields formation of a narrow ITB near r/a = 0.7 in the simulation using the current density dependent model and a wide ITB from r/a = 0.5 to 0.8 in the simulation using the ion temperature dependent model. The average of central ion temperature, total fusion power output and alpha power are predicted to be 36 keV, 159 MW and 492 MW for the current density dependent model and 49 keV, 218 MW and 786 MW for the ion temperature dependent
Forced-air warming discontinued: periprosthetic joint infection rates drop
Directory of Open Access Journals (Sweden)
Scott D. Augustine
2017-06-01
Full Text Available Several studies have shown that the waste heat from forced-air warming (FAW escapes near the floor and warms the contaminated air resident near the floor. The waste heat then forms into convection currents that rise up and contaminate the sterile field above the surgical table. It has been shown that a single airborne bacterium can cause a periprosthetic joint infection (PJI following joint replacement surgery. We retrospectively compared PJI rates during a period of FAW to a period of air-free conductive fabric electric warming (CFW at three hospitals. Surgical and antibiotic protocols were held constant. The pooled multicenter data showed a decreased PJI rate of 78% following the discontinuation of FAW and a switch to air-free CFW (n=2034; P=0.002. The 78% reduction in joint implant infections observed when FAW was discontinued suggests that there is a link between the waste FAW heat and PJIs.
FPGA Based Optimized Discontinuous SVPWM Algorithm for Three Phase VSI in AC Drives
Directory of Open Access Journals (Sweden)
Tole Sutikno
2013-02-01
Full Text Available The discontinuous space vector pulse width modulation (SVPWM has well-known that can reduce switching losses. By simplifying the thermal management issues, the discontinuous SVPWM can potentially reduce the inverter size and cost. However, using the modulation due to different time interval equations for each sector can introduce glitches at the points when the sector is changed. The more main problem, it can increase unwanted harmonic content and current ripple. Consider the decrease in switching losses associated with discontinuous modulation allows the system to utilize a higher switching frequency, this paper present high frequency switching of optimized discontinuous SVPWM based on FPGA to overcome the problems above. The proposed SVPWM has been successfully implemented by using APEX20KE Altera FPGA to drive on a three phase inverter system with 1.5 kW induction machine as load. The results have proved that the method can reduce harmonic content and current ripple without glitches.
Energy Technology Data Exchange (ETDEWEB)
Nelson, Alan J. [University of New Mexico, Albuquerque, NM; Cooper, Gary Wayne [University of New Mexico, Albuquerque, NM; Ruiz, Carlos L.; Chandler, Gordon Andrew; Fehl, David Lee; Hahn, Kelly Denise; Leeper, Ramon Joe; Smelser, Ruth Marie; Torres, Jose A.
2013-09-01
There are several machines in this country that produce short bursts of neutrons for various applications. A few examples are the Zmachine, operated by Sandia National Laboratories in Albuquerque, NM; the OMEGA Laser Facility at the University of Rochester in Rochester, NY; and the National Ignition Facility (NIF) operated by the Department of Energy at Lawrence Livermore National Laboratory in Livermore, California. They all incorporate neutron time of flight (nTOF) detectors which measure neutron yield, and the shapes of the waveforms from these detectors contain germane information about the plasma conditions that produce the neutrons. However, the signals can also be %E2%80%9Cclouded%E2%80%9D by a certain fraction of neutrons that scatter off structural components and also arrive at the detectors, thereby making analysis of the plasma conditions more difficult. These detectors operate in current mode - i.e., they have no discrimination, and all the photomultiplier anode charges are integrated rather than counted individually as they are in single event counting. Up to now, there has not been a method for modeling an nTOF detector operating in current mode. MCNPPoliMiwas developed in 2002 to simulate neutron and gammaray detection in a plastic scintillator, which produces a collision data output table about each neutron and photon interaction occurring within the scintillator; however, the postprocessing code which accompanies MCNPPoliMi assumes a detector operating in singleevent counting mode and not current mode. Therefore, the idea for this work had been born: could a new postprocessing code be written to simulate an nTOF detector operating in current mode? And if so, could this process be used to address such issues as the impact of neutron scattering on the primary signal? Also, could it possibly even identify sources of scattering (i.e., structural materials) that
Balasubramaniam, Krishnan; Ramadas, C.; Padiyar, Janardhan; Krishnamurthy, C. V.
2011-06-01
Delamination is one of the critical failure modes that laminated composites structures encounter during their fabrication and/or in-service. When guided Lamb wave (Ao) is employed for sizing of delamination, it is necessary to understand the wave interaction with the defect. Studies were carried out on the interaction of Ao mode with symmetric and asymmetric delaminations and transmission of turning modes in the sub-laminates. An attempt was also made to understand the propagation of Ao mode in composite structural T-joint. During the interaction of Ao mode with structural discontinuity in a T-joint, generation of a new mode, So, and propagation of turning modes were observed. Length and width of interface delamination in composite T-joint have been worked out using D-scan and B-scan respectively. All studied were carried out through numerical simulations and experimental verifications through Non- Contact Ultrasound (NCU) technique.
Directory of Open Access Journals (Sweden)
Anđelković Marko S.
2013-01-01
Full Text Available An experimental study has been conducted to evaluate the feasibility of a current mode gamma radiation dosimeter, consisting of a commercial PIN photodiode as a radiation sensor, and a custom made auto-ranging electrometer for real-time measurement of the PIN photodiode’s response under radiation exposure. The radiation induced direct current response for single PIN photodiodes with different active areas, as well as for multiple PIN photodiodes connected in parallel, has been investigated. Three types of commercial silicon PIN photodiodes have been chosen for evaluation - S1223, BPW34, and PS100-6-CER2 PIN. During the experiment, five samples have been tested - three samples made of single PIN photodiodes (one sample of each photodiode type and two samples formed by connecting multiple photodiodes in parallel (two BPW34 photodiodes in parallel and four BPW34 photodiodes in parallel. The samples have been irradiated with a 60Co gamma ray source and the relations between the induced photocurrent and the dose rate, and between the accumulated charge and the absorbed dose, have been determined. For measuring the photodiodes response, a custom made auto-ranging electrometer controlled by a personal computer, and capable of measuring direct currents from 50 pA to 10 mA with relative error less than 2.5%, has been used. Obtained results have shown very good linearity between the dose rate and the induced photocurrent for dose rates ranging from 0.93 Gy/h to 67 Gy/h. Also, very good linearity has been observed between the accumulated charge and the absorbed dose for all tested samples, within the investigated range of absorbed doses from 472 mGy to 3.3 Gy. On the basis of the obtained results, a simple model has been derived, enabling the estimation of the photodiode’s current response as a function of the dose rate and the photodiode’s geometry (active area and depletion layer width. [Projekat Ministarstva nauke Republike Srbije, br. 43011
Institute of Scientific and Technical Information of China (English)
周明珠; 朱恩; 王守军; 王志功; 韩鹏; 李伟
2009-01-01
描述了应用于电流模逻辑电路中的高线性度电压-电流转换电路的设计与实现.该电路采用高增益两级运算放大器构成负反馈,偏置电路利用工作在弱反型区的MOS管电压电流呈指数律关系构成PTAT(proportional to absolute temperature)基准电流源.详细分析了电阻的类型以及运算放大器的参数对线性度的影响.通过优化运算放大器的参数并采用电压系数较小的多晶硅电阻作为线性器件获得了较高的线性度.本电路已采用CSMC0.6μm CMOS工艺实现,测试结果表明:输出的总谐波失真为0.000 2%.输入动态范围为0～2.6V,输出电流为50～426 μA.PTAT基准电流源对电源变化的灵敏度为0.021 7.芯片采用5 V供电,功耗约为1.3 mW,芯片面积为0.112 mm2.%A complementary metal-oxide-senuconductor transistor (CMOS)voltage-to-current(VTC)converter with high linearity for current-mode analog and digital integrated ctrcuits is described.A high gain operational amplifier(OPA)is utilized to form negative feedback.A proportional to absolute temperature (PTAT)current reference with transistors operated in a weak inversion is used as the bias circuit.The resistor and the OPA nonlinearity behavior are analyzed in detail.By optimizing parameters in OPA and adopting a small voltage coefficient poly-silicon resistor as a linear device,a high linearity is achieved.The circuit is implemented in a standard 0.6 μm CMOS technology.The low frequency gain of the OPA exceeds 90 dB.The test results indicate that the total harmonic distortion(THD))is 0.000 2%.The common-mode input linearity range is 0 to 2.6V.Correspondingly,the output current range is 50 to 426μA.The sensitivity of the PTAT current reference to Vdd is approximately 0.021 7.The chip consumes a power oflessthan 1.3 mW for a 5V supply.and occupies an area of0.112 mm2
电流模式可重构模拟信号处理电路%Current-Mode Reconfigurable Analog Circuit for Analog Signal Processing
Institute of Scientific and Technical Information of China (English)
王友仁; 祝鸣涛; 崔江; 林华; 姜媛媛
2011-01-01
There are problems of limited function, low operational speed and insufficient flexibility in the conventional reconfigurable analog circuits. A new current-mode reconfigurable analog circuit is proposed to solve them. The configurable analog block (CAB) based on second-generation current controlled conveyor (CCCII) is designed, which has the advantages of smaller nonlinear distortion, higher operational speed and better anti-interference ability. A new crossbar switch inter-connection network is developed, which can reduce the number of switches, and improve the flexibility and high frequency response of the reconfigurable analog circuit. The forth-order butterworth low-pass filter (LPF) and the analog multiplier are reconfigured with 2X4 reconfigurable analog circuit array. The experimental results show that the proposed reconfigurable analog circuit can effectively realize analog signal processing circuits of different functions through reconfiguration.%针对现有的可重构模拟电路存在功能有限、带宽小、灵活性不足等同题,设计了一种新的电流模式可重构模拟电路.设计了基于二代电流传输控制器的可重构模拟单元,能减小电路非线性失真,提高电路工作速度与抗干扰能力.设计了一种可编程开关数量较少的纵横交叉开关网络结构,提高了电路灵活性和高频性能.在2×4一阵列结构上分别重构实现了四阶低通滤波器和模拟乘法器,实验结果表明所设计可重构模拟电路是有效的.
Institute of Scientific and Technical Information of China (English)
房玉伟; 吉洪湖; 薛占奎; 胡谷琅; 闫川; 杜佳; 丁祥海
2013-01-01
The current status of planting mode for early and late rice in the double-cropping rice system in Jinhua City was introduced.The grain yield,production costs and returns of different planting modes widely adopted by large-scaled growers in the double-cropping rice system were surveyed.The strength and weakness were compared among different planting modes including the direct seeding mode and the mechanized transplanting mode for both early and late rice and the handed transplanting mode for late rice.It is concluded that direct seeding and mechanized transplanting will be the major planting modes for early rice while mechanized transplanting will be the dominant planting mode,with direct seeding as a supplementary,for late rice in Jinhua City for large-scaled growers in the future.%介绍了金华市双季稻稻作方式的现状以及目前规模种植大户双季稻不同稻作方式的产量、生产成本和效益,分析了早晚稻直播、早晚稻机插和晚稻手插等稻作方式的优点和缺点,指出未来规模种粮大户在稻作方式的选择上,早稻应以直播和机插为主,晚稻以机插为主,直播为辅.
Energy Technology Data Exchange (ETDEWEB)
Krit, Salahddine; Qjidaa, Hassan; Affar, Imad El; Khadija, Yafrah; Messghati, Ziani; El-Ghzizal, Yassir, E-mail: krit_salah@yahoo.f, E-mail: qjidah@yahoo.f [Faculty of Sciences Dhar El Mehraz, Laboratory of Electronic, Signal-Systymes and Informatic (LESSI) Fes (Morocco)
2010-04-15
This paper presents a novel organization of switch capacitor charge pump circuits based on voltage doubler structures. Each voltage doubler takes a DC input and outputs a doubled DC voltage. By cascading voltage doublers the output voltage increases up to 2 times. A two-phase voltage doubler and a multiphase voltage doubler structures are discussed and design considerations are presented. A simulator working in the Q-V realm was used for simplified circuit level simulation. In order to evaluate the power delivered by a charge pump, a resistive load is attached to the output of the charge pump and an equivalent capacitance is evaluated. To avoid the short circuit during switching, a clock pair generator is used to achieve multi-phase non-overlapping clock pairs. This paper also identifies optimum loading conditions for different configurations of the charge pumps. The proposed charge-pump circuit is designed and simulated by SPICE with TSMC 0.35-{mu}m CMOS technology and operates with a 2.7 to 3.6 V supply voltage. It has an area of 0.4 mm{sup 2}; it was designed with a frequency regulation of 1 MHz and internal current mode to reduce power consumption. (semiconductor integrated circuits)
Directory of Open Access Journals (Sweden)
A.B. Chattopadhyay
2014-02-01
Full Text Available Modeling of synchronous motor plays a dominant role in designing complicated drive system for different applications, especially large blower fans etc for steel industries. As synchronous motor has no inherent starting torque generally it is started as an induction motor with the help of a damper winding and it pulls into synchronism under certain conditions. The present paper exactly concentrates on this particular zone of transition from induction motor to synchronous motor mode for a current source inverter fed synchronous motor drive system. Due to complexity of synchronous motor in terms of number of windings and finite amount of air gap saliency, direct modeling of such transition zone in time domain becomes cumbersome at the first instance of modeling. That is why the modeling in complex frequency domain (s-domain has been taken up using small perturbation model. Such a model clearly shows role of induction motor as noise function or disturbance function with respect to the open loop block diagram of synchronous motor. Such finding can be quantized in terms of important results and that is done in the present paper such that the results can help the designer for the successful design of a synchronous motor drive system.
Gu, Binbin; Zhang, Yanying; Ding, Lijian; He, Shan; Wu, Bin; Dong, Junde; Zhu, Peng; Chen, Juanjuan; Zhang, Jinrong; Yan, Xiaojun
2015-01-09
High-speed counter-current chromatography (HSCCC) was successively applied to the separation of three sulfur-containing diketopiperazines (DKPs) (including two new compounds cladosporin A (1) and cladosporin B (3), and a known compound haematocin (2)) from a marine fungus Cladosporium sp. The two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water at (1:1:1:1, v/v) and (2:1:2:1, v/v), in stepwise elution mode, was used for HSCCC. The preparative HSCCC separation was performed on 300 mg of crude sample yielding 26.7 mg of compound 3 at a purity of over 95%, 53.6 mg of a mixture of compounds 1 and 2, which was further separated by preparative-HPLC yielding 14.3 mg of compound 1 and 25.4 mg of compound 2 each at a purity of over 95%. Their structures were established by spectroscopic methods. The sulfur-containing DKPs suppressed the proliferation of hepatocellular carcinoma cell line HepG2. The present work represents the first application of HSCCC in the efficient preparation of marine fungal natural products.
Directory of Open Access Journals (Sweden)
A.B. Chattopadhyay
2014-10-01
Full Text Available Modeling of synchronous motor plays a dominant role in designing complicated drive system for different applications, especially large blower fans etc., for steel industries. As synchronous motor has no inherent starting torque generally it is started as an induction motor with the help of a damper winding and it pulls into synchronism under certain conditions. The present study exactly concentrates on this particular zone of transition from induction motor to synchronous motor mode for a current source inverter fed synchronous motor drive system. Due to complexity of synchronous motor in terms of number of windings and finite amount of air gap saliency, direct modeling of such transition zone in time domain becomes cumbersome at the first instance of modeling. That is why firstly the modeling is presented in complex frequency domain and then the time domain modeling is obtained by applying inverse Laplace transform technique. Apparently it seems to be a straight forward mathematical treatment but involvement of Convolution Integral for converting the formulation from s-domain to time domain becomes a matter of interest and it may draw the attention of various researchers working in this area. Furthermore the time domain response of the disturbance function may help a designer to fix up the time instant when the pull in phenomenon will be imposed by throwing the field winding to a DC supply.
Ollivier-Henry, N; Wu Gao; Xiaochao Fang; Mbow, N A; Brasse, D; Humbert, B; Hu-Guo, C; Colledani, C; Yann Hu
2011-02-01
This paper presents the design and characteristics of a front-end readout application-specific integrated circuit (ASIC) dedicated to a multichannel-plate photodetector coupled to LYSO scintillating crystals. In our configuration, the crystals are oriented in the axial direction readout on both sides by individual photodetector channels allowing the spatial resolution and the detection efficiency to be independent of each other. Both energy signals and timing triggers from the photodetectors are required to be read out by the front-end ASIC. A current-mode charge-sensitive amplifier is proposed for this application. This paper presents performance characteristics of a 10-channel prototype chip designed and fabricated in a 0.35-μm complementary metal-oxide semiconductor process. The main results of simulations and measurements are presented and discussed. The gain of the chip is 13.1 mV/pC while the peak time of a CR-RC pulse shaper is 280 ns. The signal-to-noise ratio is 39 dB and the rms noise is 300 μV/√(Hz). The nonlinearity is less than 3% and the crosstalk is about 0.2%. The power dissipation is less than 15 mW/channel. This prototype will be extended to a 64-channel circuit with integrated time-to-digital converter and analog-to-digital converter together for a high-sensitive small-animal positron emission tomography imaging system.
Directory of Open Access Journals (Sweden)
Binbin Gu
2015-01-01
Full Text Available High-speed counter-current chromatography (HSCCC was successively applied to the separation of three sulfur-containing diketopiperazines (DKPs (including two new compounds cladosporin A (1 and cladosporin B (3, and a known compound haematocin (2 from a marine fungus Cladosporium sp. The two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water at (1:1:1:1, v/v and (2:1:2:1, v/v, in stepwise elution mode, was used for HSCCC. The preparative HSCCC separation was performed on 300 mg of crude sample yielding 26.7 mg of compound 3 at a purity of over 95%, 53.6 mg of a mixture of compounds 1 and 2, which was further separated by preparative-HPLC yielding 14.3 mg of compound 1 and 25.4 mg of compound 2 each at a purity of over 95%. Their structures were established by spectroscopic methods. The sulfur-containing DKPs suppressed the proliferation of hepatocellular carcinoma cell line HepG2. The present work represents the first application of HSCCC in the efficient preparation of marine fungal natural products.
Discontinuous Galerkin Method for Hyperbolic Conservation Laws
Mousikou, Ioanna
2016-11-11
Hyperbolic conservation laws form a special class of partial differential equations. They describe phenomena that involve conserved quantities and their solutions show discontinuities which reflect the formation of shock waves. We consider one-dimensional systems of hyperbolic conservation laws and produce approximations using finite difference, finite volume and finite element methods. Due to stability issues of classical finite element methods for hyperbolic conservation laws, we study the discontinuous Galerkin method, which was recently introduced. The method involves completely discontinuous basis functions across each element and it can be considered as a combination of finite volume and finite element methods. We illustrate the implementation of discontinuous Galerkin method using Legendre polynomials, in case of scalar equations and in case of quasi-linear systems, and we review important theoretical results about stability and convergence of the method. The applications of finite volume and discontinuous Galerkin methods to linear and non-linear scalar equations, as well as to the system of elastodynamics, are exhibited.
Discontinuation Decision in Assisted Reproductive Techniques
Directory of Open Access Journals (Sweden)
Ashraf Moini
2009-01-01
Full Text Available Background: In vitro fertilization (IVF and intra cytoplasmic sperm injection (ICSI are recognizedas established and increasingly successful forms of treatment for infertility, yet significant numbersof couples discontinue treatment without achieving a live birth. This study aims to identify majorfactors that influence the decision to discontinue IVF/ICSI treatments.Materials and Methods: We studied the data of 338 couples who discontinued their infertilitytreatments after three cycles; based on medical records and phone contact. The main measure wasthe reason for stopping their treatments.Results: Economical problems were cited by 212 couples (62.7%, as their mean income wassignificantly less than other couples (p<0.0001. Lack of success was reported as a reason by229 (67.8%, from whom 165 (72% also had economical problems. Achieving independent-ART pregnancy was the reason for discontinuation in 20 (5.9% couples. Psychological stress,depression and anxiety were reported as other cessation factors by 169 (50%, 148 (43.8% and 182(53.8% couples, respectively.Conclusion: This survey suggests that the most common reasons for assisted reproductivetechnique (ART discontinuation after three cycles are: prior unsuccessful cycles, economicaland psychological problems. Therefore, the substantial proportion of couples could benefit frompsychological intervention, increasing awareness of ART outcomes and health funding to copemore adequately with failed treatments.
27 CFR 555.128 - Discontinuance of business.
2010-04-01
... 27 Alcohol, Tobacco Products and Firearms 3 2010-04-01 2010-04-01 false Discontinuance of business... Discontinuance of business. Where an explosive materials business or operations is discontinued and succeeded by... such facts and shall be delivered to the successor. Where discontinuance of the business or operations...
27 CFR 478.127 - Discontinuance of business.
2010-04-01
... 27 Alcohol, Tobacco Products and Firearms 3 2010-04-01 2010-04-01 false Discontinuance of business... Records § 478.127 Discontinuance of business. Where a licensed business is discontinued and succeeded by a... be delivered to the successor. Where discontinuance of the business is absolute, the records shall be...
27 CFR 478.57 - Discontinuance of business.
2010-04-01
... 27 Alcohol, Tobacco Products and Firearms 3 2010-04-01 2010-04-01 false Discontinuance of business... Licenses § 478.57 Discontinuance of business. (a) Where a firearm or ammunition business is either discontinued or succeeded by a new owner, the owner of the business discontinued or succeeded shall within 30...
PLASTIC LIMIT ANALYSIS OF DISCONTINUOUS LINING UNDERGROUND PRESSURE
Institute of Scientific and Technical Information of China (English)
龙春安
1999-01-01
Discontinuous lining is a special form of support in underground excavation. Based on the method of plastic limit analysis, it is found the upper and the lower bound solution of the pressure of circular discontinuous lining and discussed support parameter of discontinuous lining and its applicable conditions, which provides theoretical basis for the design and calculation of discontinuous lining.
Homentcovschi, Dorel; Miles, Ronald N.
2012-01-01
The paper applies the re-expansion method for analyzing planar discontinuities at the junction of two axi-symmetrical circular waveguides. The normal modes in the two waveguides are expanded at the junction plane into a system of functions accounting for velocity singularities at the corner points. As the new expansion has a high convergence order, only a few terms have to be considered for obtaining the solution of most practical problems. This paper gives the equivalent impedance accounting for nonplanar waves into a plane-wave analysis and also the scattering matrix describing the coupling of arbitrary modes at each side of the discontinuity valid in the case of many propagating modes in both sides of the duct. The last section applies the re-expansion technique to some concentric expansion chambers providing an explicit formula for the transmission loss coefficient. PMID:22352491
Upper mantle seismic discontinuities in the area of the Indian Ocean Geoid Low
Reiss, Anne-Sophie; van Driel, Jac; Heyn, Björn; Thomas, Christine
2017-04-01
We are investigating the upper mantle seismic discontinuities at 410 and 660 km depth beneath the southern tip of India, where the Indian Ocean Geoid Low (IOGL) is located. We use PP and SS waves and their precursors, which reflect off the underside of these seismic discontinuities midway between source and receiver, to map the topography of the two discontinuities bounding the mantle transition zone. Our dataset consists of 9604 events with magnitude 5.8 or higher recorded at 57 different arrays distributed around the Indian Ocean. This results in a dense coverage of reflection points across our area of interest. 599 events out of this dataset show a good PP or SS signal. To enhance the signal-to-noise-ratio for better visibility of the weak precursor signals and to identify out-of-plane arrivals we use array seismology methods. We obtain the depth of the discontinuities by measuring the differential travel time between the main phase and the precursor signal, comparing it with theoretical travel times through the 1D reference Earth model ak135 and correcting the measured travel times for crustal and tomographic features. Most of the signals we observe reflect off the 410 km discontinuity, which is caused by the solid-solid phase transition from olivine to wadsleyite. The 660 km discontinuity, which exists due to the phase transformation from ringwoodite to bridgmanite and magnesiowustite, also causes some visible reflections in our dataset. Besides those two discontinuities we also see few reflections both from shallower and deeper structure. The best quality data show a deepened 410 in the centre of the IOGL as well as an overall elevated 660 km discontinuity. The combined observation of the IOGL, its sensitivity kernel and the behaviour of the mantle transition zone seismic discontinuities can be interpreted as a hot upwelling that currently resides in the mantle transition zone.
Yoshida, Kazuki; Radner, Helga; Kavanaugh, Arthur; Sung, Yoon-Kyoung; Bae, Sang-Cheol; Kishimoto, Mitsumasa; Matsui, Kazuo; Okada, Masato; Tohma, Shigeto; Weinblatt, Michael E.; Solomon, Daniel H.
2016-01-01
Many biologic disease-modifying antirheumatic drug (DMARD) discontinuation studies have been conducted, but mainly in trial settings which result in limited generalizability. Registry studies can complement the current literature of biologic DMARD discontinuation by providing more generalizable information. However, registries may need to be combined to increase power and provide a more diverse patient population. This increased power could provide us information about risk and benefits of discontinuing biologic DMARD in typical clinical practice. However, use of multiple registries is not without challenges. In this review, we discuss the challenges to combining data across multiple registries, focusing on biologic discontinuation as an example. Challenges include: 1) generalizability of each registry; 2) new versus prevalent users designs; 3) outcome definitions; 4) different health care systems; 5) different follow up intervals; and 6) data harmonization. The first three apply to each registry, and the last three apply to combining multiple registries. This review describes these challenges, corresponding solutions, and potential future opportunities. PMID:24129133
Method for simulating discontinuous physical systems
Baty, Roy S.; Vaughn, Mark R.
2001-01-01
The mathematical foundations of conventional numerical simulation of physical systems provide no consistent description of the behavior of such systems when subjected to discontinuous physical influences. As a result, the numerical simulation of such problems requires ad hoc encoding of specific experimental results in order to address the behavior of such discontinuous physical systems. In the present invention, these foundations are replaced by a new combination of generalized function theory and nonstandard analysis. The result is a class of new approaches to the numerical simulation of physical systems which allows the accurate and well-behaved simulation of discontinuous and other difficult physical systems, as well as simpler physical systems. Applications of this new class of numerical simulation techniques to process control, robotics, and apparatus design are outlined.
Identification of discontinuities in plasma plume evolution
Gojani, Ardian B; Obayashi, Shigeru
2013-01-01
The ejection of material during laser ablation gives rise to the development of discontinuities in the ambient gas. Several of these discontinuities are observed and characterized, including externally and internally propagating shock waves, contact surface, and the ionization front. Qualitative experimental observations and analysis of these discontinuities is presented. Results from shadowgraphy enabled determination of an irradiance threshold between two different ablation mechanisms, and determination of several stages of plasma plume evolution. Consideration of the refractive index as a dynamic sum of the contributions from gas and electrons led to separate identification of ionization front from the contact surface. Furthermore, ionization front was observed to lead the shock wave at the earlier stage of the ablation.
Seismic imaging of a mid-lithospheric discontinuity beneath Ontong Java Plateau
Tharimena, Saikiran; Rychert, Catherine A.; Harmon, Nicholas
2016-09-01
Ontong Java Plateau (OJP) is a huge, completely submerged volcanic edifice that is hypothesized to have formed during large plume melting events ∼90 and 120 My ago. It is currently resisting subduction into the North Solomon trench. The size and buoyancy of the plateau along with its history of plume melting and current interaction with a subduction zone are all similar to the characteristics and hypothesized mechanisms of continent formation. However, the plateau is remote, and enigmatic, and its proto-continent potential is debated. We use SS precursors to image seismic discontinuity structure beneath Ontong Java Plateau. We image a velocity increase with depth at 28 ± 4 km consistent with the Moho. In addition, we image velocity decreases at 80 ± 5 km and 282 ± 7 km depth. Discontinuities at 60-100 km depth are frequently observed both beneath the oceans and the continents. However, the discontinuity at 282 km is anomalous in comparison to surrounding oceanic regions; in the context of previous results it may suggest a thick viscous root beneath OJP. If such a root exists, then the discontinuity at 80 km bears some similarity to the mid-lithospheric discontinuities (MLDs) observed beneath continents. One possibility is that plume melting events, similar to that which formed OJP, may cause discontinuities in the MLD depth range. Plume-plate interaction could be a mechanism for MLD formation in some continents in the Archean prior to the onset of subduction.
Rockburst Generation in Discontinuous Rock Masses
He, Ben-Guo; Zelig, Ravit; Hatzor, Yossef H.; Feng, Xia-Ting
2016-10-01
We study rockburst generation in discontinuous rock masses using theoretical and numerical approaches. We begin by developing an analytical solution for the energy change due to tunneling in a continuous rock mass using linear elasticity. We show that the affected zone where most of the increase in elastic strain energy takes place is restricted to an annulus that extends to a distance of three diameters from the tunnel center, regardless of initial tunnel diameter, magnitude of in situ stress, and in situ stress ratio. By considering local elastic strain concentrations, we further delineate the Rockbursting Prone Zone found to be concentrated in an annulus that extends to one diameter from the tunnel center, regardless of original stress ratio, magnitude, and the stiffness of the rock mass. We proceed by arguing that in initially discontinuous rock masses shear stress amplification due to tunneling will inevitably trigger block displacements along preexisting discontinuities much before shear failure of intact rock elements will ensue, because of the lower shear strength of discontinuities with respect to intact rock elements, provided of course that the blocks are removable. We employ the numerical discrete element DDA method to obtain, quantitatively, the kinetic energy, the elastic strain energy, and the dissipated energy in the affected zone in a discontinuous rock due to tunneling. We show that the kinetic energy of ejected blocks due to strain relaxation increases with increasing initial stress and with decreasing frictional resistance of preexisting discontinuities. Finally, we demonstrate how controlled strain energy release by means of top heading and bench excavation methodology can assist in mitigating rockburst hazards due to stain relaxation.
Design of current-mode integrator unit based on OTA%基于跨导放大器的电流模式积分单元的设计
Institute of Scientific and Technical Information of China (English)
姚博; 于海勋; 王耀文
2012-01-01
In the integrated circuit system, each current unit with analog function is composed of the basic current mode units. OTA (Operational Transconductance Amplifier) that is a basic unit in current-mode circuit system. The current integral conversion from current to current can be realized by current-mode integrator base on OTA. The integrator can also be applied to the design of various integrated filtering circuits. In this paper, a high power gain and low power consumption OTA with the power supply voltage of 1. 8 V is designed by using 1. 8 μm CMOS simulation process and cascode structure, based on. A bias circuit base on PTAT reference current source is also used in the circuit. The design process is optimized with Hspice. The OTA is adopted in the current simulation of a current mode integral unit.%在集成电路系统中,各种模拟功能的电流单元都是由基本的电流模单元组成.跨导放大器是电流模电路的基本单元.基于跨导放大器的电流模积分器可以实现电流到电流的积分转换.同时可应用于各种集成滤波电路的设计.在此采用0.18 μm CMOS仿真工艺,使用共源共栅结构设计一款供电电压为1.8V的高增益低功耗的跨导放大器,采用具有PTAT基准电流源的偏置电路,使用HSpice进行优化设计,并将此放大器应用于电流模式积分单元的电路仿真.
Discontinuity-preserving optical flow algorithm
Institute of Scientific and Technical Information of China (English)
Yuan Lei; Li Jinzong; Li Dongdong
2007-01-01
A modification of Horn and Schunk's approach is investigated, which leads to a better preservation of flow discontinuities.It improves Horn-Schunk model in three aspects: (1) It replaces the smooth weight coefficient in the energy equation by the variable weight coefficient.(2) It adopts a novel method to compute the mean velocity.The novel method also reflects the effect of the intensity difference on the image velocity diffusion.(3) It introduces a more efficient iterative method than the Gauss-Seidel method to solve the associated Euler-Lagrange equation.The experiment results validate the better effect of the improved method on preserving discontinuities.
Discontinuity effects on radial cavity transmission lines
Energy Technology Data Exchange (ETDEWEB)
Seidel, D.B.
1979-04-01
Pulse propagation in radial cavity transmission lines such as those found on a radial line accelerator is considered. Specifically, the effects of discontinuities along the line are examined in detail. It is found that previous analyses of such effects have been incorrect, and here two alternate solution techniques are presented. Depending upon the parameters of such a radial line, the discontinuity effects considered here may or may not be significant; however, if they are significant, it is recommended that the alternate solution techniques presented here be used.
Pupil phase discontinuity measurement: comparison of different wavefront sensing concepts
El Hadi, K.; Sauvage, J.-F.; Dohlen, K.; Fusco, T.; Neichel, B.; Marchis, F.; N'Diaye, M.
2016-07-01
The Laboratoire d'Astrophysique de Marseille is involved in the preparation of the E-ELT instrumentation framework: In particular, an ESO-EELT M1 mirror segment (1.5 m) has been demonstrated and different wavefront sensing (WFS) concepts among which Pyramid, Zernike phase mask sensor (ZELDA), Phase diversity or still NL Curvature) are also investigated. Segmented mirrors are widely used today in diverse domains: fiber coupling, laser beam shaping, microscopy or retina imaging. If, these mirrors offer a solution to realize important monolithic sizes for giant telescopes in astronomy, they also raise the problem of segments cophasing and measurement of phase discontinuities. In this work, we aim to investigate a suitable WFS approach for pupil phase discontinuity measurement. Coupling a segmented PTT mirror (Iris AO) with four different WFS (Shack-Hartmann, Quadriwave Lateral Shearing Interferometer, Pyramid and Zernike Phase Mask), we study their sensitivity to segmented pupil: in particular, segment phasing, stability, saturation, flat, or still the addressing mode are then performed and compared.
Hermance, J. F.
1984-01-01
Electromagnetic induction in a laterally homogeneous earth is analyzed in terms of a source field with finite dimensions. Attention is focused on a time-varying two-dimensional current source directed parallel to the strike of a two-dimensional anomalous structure within the earth, i.e., the E-parallel mode. The spatially harmonic source field is expressed as discontinuities in the magnetic (or electric) field of the current in the source. The model is applied to describing the magnetic gradients across megatectonic features, and may be used to predict the magnetic fields encountered by a satellite orbiting above the ionosphere.
On the propagation of jump discontinuities in relativistic cosmology
Van Elst, H; Schmidt, B G; Elst, Henk van; Ellis, George F R; Schmidt, Bernd G
2000-01-01
A recent dynamical formulation at derivative level $\\ptl^{3}g$ for fluid spacetime geometries $({\\cal M}, {\\bf g}, {\\bf u})$, that employs the concept of evolution systems in first-order symmetric hyperbolic format, implies the existence in the Weyl curvature branch of a set of timelike characteristic 3-surfaces associated with propagation speed $| v | = \\sfrac{1}{2}$ relative to fluid-comoving observers. We show it is the physical role of the constraint equations to prevent realisation of jump discontinuities in the derivatives of the related initial data so that Weyl curvature modes propagating along these 3-surfaces cannot be activated. In addition we introduce a new, illustrative first-order symmetric hyperbolic evolution system at derivative level $\\ptl^{2}g$ for baryotropic perfect fluid cosmological models that are invariant under the transformations of an Abelian $G_{2}$ isometry group.
Dynamic Discontinuous Control for Active Control of Mechanical Vibrations
Directory of Open Access Journals (Sweden)
Orestes Llanes Santiago
2010-02-01
Full Text Available This article shows the use of the discontinuous control using dynamic sliding modes for the active isolation of vibrations in mechanical systems. This type of control law constitutes a robust feedback control policy due to its insensitivity to external disturbance inputs, certain immunity to model parameter variations, within known bounds, and to the ever present modelling errors. The whole theoretical analysis is applied to a lineal model of two degrees of freedom of the vehicle's suspension where the irregularities of the land represent of direct way the external interferences to the system . To carry out the isolation an electro-hydraulic operator it is used. Simulations are performed which validate the proposed approach.
77 FR 26185 - POSTNET Barcode Discontinuation
2012-05-03
... From the Federal Register Online via the Government Publishing Office ] POSTAL SERVICE 39 CFR Part 111 POSTNET Barcode Discontinuation AGENCY: Postal Service TM . ACTION: Final rule. SUMMARY: The... March 2, 2012, the Postal Service published a proposed rule in the Federal Register (77 FR 12764-12769...
Problems with Discontinuous Diffusion/Dispersion Coefficients
Directory of Open Access Journals (Sweden)
Stefano Ferraris
2012-01-01
accurate on smooth solutions and based on a special numerical treatment of the diffusion/dispersion coefficients that makes its application possible also when such coefficients are discontinuous. Numerical experiments confirm the convergence of the numerical approximation and show a good behavior on a set of benchmark problems in two space dimensions.
General practitioners’ decisions about discontinuation of medication
DEFF Research Database (Denmark)
Nixon, Michael Simon; Vendelø, Morten Thanning
2016-01-01
Purpose – The purpose of this paper is to investigate how general practitioners’ (GPs) decisions about discontinuation of medication are influenced by their institutional context. Design/methodology/approach – In total, 24 GPs were interviewed, three practices were observed and documents were col...
Continuous-Discontinuous Modelling of Failure
Simone, A.
2003-01-01
The foundations of a safe structural design lie on the understanding of failure processes of engineering materials and in their correct representation. In a numerical context, failure representation in engineering materials can be pursued either in a continuous or in a discontinuous setting. Both ap
ELECTRIC FIELD MEASUREMENT IN ROD-DISCONTINUED ...
African Journals Online (AJOL)
2014-06-30
Jun 30, 2014 ... The used arrangement with homogeneous system is made up of a square metallic sheet ... This distance is considered positive when the rod is located ... in the case of the discontinuous earth which were defined according to ...
An equilibrium closure result for discontinuous games
Balder, E.J.
2011-01-01
For games with discontinuous payoffs Simon and Zame (1990) introduced payoff indeterminacy, in the form of endogenous sharing rules, which are measurable selections of a certain payoff correspondence. Their main result concerns the existence of a mixed Nash equilibrium and an associated sharing
Olanzapine discontinuation emergent recurrence in bipolar disorder
Directory of Open Access Journals (Sweden)
Manu Arora
2014-01-01
Full Text Available Objective: The efficacy of atypical antipsychotics including olanzapine in acute treatment of manic episode has been established, whereas its role in maintenance treatment is not clear. Materials and Methods: Thirteen patients of bipolar disorder who were on regular treatment with mood stabilizer and subsequently relapsed into mania or depressive episode after discontinuation of olanzapine were studied for various socio-demographic and clinical factors using retrospective chart review. Results: There was no correlation found between the period of tapering olanzapine, time to recurrence of episode after discontinuation, and the dosage of olanzapine at the time of discontinuation. The predominant early signs of relapse after discontinuation of olanzapine included sleep disturbance (72.7%, lack of insight for change in behavior (72.7%, irritability (54.5%, and elevated mood (45.5%. Conclusion: Mood stabilizer alone as a maintenance therapy of bipolar disorder may be inadequate for long-term management. A low dose of olanzapine along with mood stabilizers might be useful for prevention of recurrence in bipolar disorder.
Discontinued drugs in 2008: endocrine and metabolic.
Colca, Jerry R
2009-09-01
This perspective summarizes key compounds from the endocrine and metabolic area that were discontinued during the calendar year 2008. This is a continuation in a series of perspectives of each of the editorial areas summarized by Expert Opinion on Investigational Drugs. The candidates covered in this summary were being developed for the treatment of diabetes, diabetic complications, anti-atherosclerosis and obesity.
Unstructured discontinuous Galerkin for seismic inversion.
Energy Technology Data Exchange (ETDEWEB)
van Bloemen Waanders, Bart Gustaaf; Ober, Curtis Curry; Collis, Samuel Scott
2010-04-01
This abstract explores the potential advantages of discontinuous Galerkin (DG) methods for the time-domain inversion of media parameters within the earth's interior. In particular, DG methods enable local polynomial refinement to better capture localized geological features within an area of interest while also allowing the use of unstructured meshes that can accurately capture discontinuous material interfaces. This abstract describes our initial findings when using DG methods combined with Runge-Kutta time integration and adjoint-based optimization algorithms for full-waveform inversion. Our initial results suggest that DG methods allow great flexibility in matching the media characteristics (faults, ocean bottom and salt structures) while also providing higher fidelity representations in target regions. Time-domain inversion using discontinuous Galerkin on unstructured meshes and with local polynomial refinement is shown to better capture localized geological features and accurately capture discontinuous-material interfaces. These approaches provide the ability to surgically refine representations in order to improve predicted models for specific geological features. Our future work will entail automated extensions to directly incorporate local refinement and adaptive unstructured meshes within the inversion process.
Excursions in fluvial (dis)continuity
Grant, Gordon E.; O'Connor, James E.; Safran, Elizabeth
2017-01-01
Lurking below the twin concepts of connectivity and disconnectivity are their first, and in some ways, richer cousins: continuity and discontinuity. In this paper we explore how continuity and discontinuity represent fundamental and complementary perspectives in fluvial geomorphology, and how these perspectives inform and underlie our conceptions of connectivity in landscapes and rivers. We examine the historical roots of continuum and discontinuum thinking, and how much of our understanding of geomorphology rests on contrasting views of continuity and discontinuity. By continuum thinking we refer to a conception of geomorphic processes as well as geomorphic features that are expressed along continuous gradients without abrupt changes, transitions, or thresholds. Balance of forces, graded streams, and hydraulic geometry are all examples of this perspective. The continuum view has played a prominent role in diverse disciplinary fields, including ecology, paleontology, and evolutionary biology, in large part because it allows us to treat complex phenomena as orderly progressions and invoke or assume equilibrium processes that introduce order and prediction into our sciences.In contrast the discontinuous view is a distinct though complementary conceptual framework that incorporates non-uniform, non-progressive, and non-equilibrium thinking into understanding geomorphic processes and landscapes. We distinguish and discuss examples of three different ways in which discontinuous thinking can be expressed: 1) discontinuous spatial arrangements or singular events; 2) specific process domains generally associated with thresholds, either intrinsic or extrinsic; and 3) physical dynamics or changes in state, again often threshold-linked. In moving beyond the continuous perspective, a fertile set of ideas comes into focus: thresholds, non-equilibrium states, heterogeneity, catastrophe. The range of phenomena that is thereby opened up to scientific exploration similarly expands
In-process discontinuity detection during friction stir welding
Shrivastava, Amber
The objective of this work is to develop a method for detecting the creation of discontinuities (e.g., voids) during friction stir welding. Friction stir welding is inherently cost-effective, however, the need for significant weld inspection can make the process cost-prohibitive. A new approach to weld inspection is required -- where an in-situ characterization of weld quality can be obtained, reducing the need for post-process inspection. Friction stir welds with discontinuity and without discontinuity were created. In this work, discontinuities are generated by reducing the friction stir tool rotation frequency and increasing the tool traverse speed in order to create "colder" welds. During the welds, forces are measured. Discontinuity sizes for welds are measured by computerized tomography. The relationship between the force transients and the discontinuity sizes indicate that the force measurement during friction stir welding can be effectively used for detecting discontinuities in friction stir welds. The normalized force transient data and normalized discontinuity size are correlated to develop a criterion for discontinuity detection. Additional welds are performed to validate the discontinuity detection method. The discontinuity sizes estimated by the force measurement based method are in good agreement with the discontinuity sizes measured by computerized tomography. These results show that the force measurement based discontinuity detection model method can be effectively used to detect discontinuities during friction stir welding.
Diffractional Imaging of Mantle Transition Zone Discontinuities Using SdS-SS Traveltimes
Guo, Z.; Zhou, Y.
2015-12-01
The mantle transition zone is characterized by two discontinuities at depths of about 410 and 660 km. Mineral physics studies suggest that wavespeed and density jumps across the discontinuities are associated with olivine phase transformations and the depths at which the phase transformations occur are strongly dependent on temperature. Imaging lateral variations of the discontinuity depths is important for constraining thermal structure in the mid mantle. SS precursors (SdS) are waves reflected at the underside of the discontinuities and arrive beforethe SS phase. Their traveltime measurements at teleseismic distances can be used to map the discontinuities at a global scale. In this study, we measure frequency-dependent SS precursors traveltimes using seismograms recorded at GSN stations for earthquakes occurred between 2000 and 2015. The measurements were made using cosine tapers and multitapers and the traveltimes show significant dispersion. We calculate finite-frequency sensitivity kernels for SdS-SS differential measurements based on traveling-wave mode summation, which account for complete wave interactions within the measurement window. We will discuss preliminary results from finite-frequency imaging using SdS-SS dispersion measurements and the effects of 3-D crustal structure and mantle wavespeed structure.
Double plate system with a discontinuity in the elastic bonding layer
Institute of Scientific and Technical Information of China (English)
Katica (Stevanovi(c)) Hedrih
2007-01-01
The double plate system with a discontinuity in the elastic bonding layer of Winker type is studied in this paper. When the discontinuity is small, it can be taken as an interface crack between the bi-materials or two bodies (plates or beams). By comparison between the number of multifrequencies of analytical solutions of the double plate system free transversal vibrations for the case when the system is with and without discontinuity in elastic layer we obtain a theory for experimental vibration method for identification of the presence of an interface crack in the double plate system. The analytical analysis of free transversal vibrations of an elastically connected double plate systems with discontinuity in the elastic layer of Winkler type is presented. The analytical solutions of the coupled partial differential equations for dynamical free and forced vibration processes are obtained by using method of Bernoulli's particular integral and Lagrange's method of variation constants. It is shown that one mode vibration corresponds an infinite or finite multi-frequency regime for free and forced vibrations induced by initial conditions and onefrequency or corresponding number of multi-frequency regime depending on external excitations. It is shown for every shape of vibrations. The analytical solutions show that the discontinuity affects the appearance of multi-frequency regime of time function corresponding to one eigen amplitude function of one mode, and also that time functions of different vibration basic modes are coupled. From final expression we can separate the new generalized eigen amplitude functions with corresponding time eigen functions of one frequency and multifrequency regime of vibrations.
Energy Technology Data Exchange (ETDEWEB)
Glotzbecker, Ryan Joseph [Pennsylvania State Univ., University Park, PA (United States)
2006-05-01
Experimental, numerical, and analytical work has shown that the response of a shell to a distributed force wave possesses unique characteristics which are dependent on the nature of structure attached to the shell. Specific characteristics which influence the response are the distribution of the discontinuities around the circumference (periodic/aperiodic), the impedance of the discontinuities relative to that of the shell, and the type of impedance (mass or stiffness). Traditional shell theory predicts low frequency, radial-dominated structural mode shapes of a shell with a sinusoidal distribution of displacement amplitudes. Due to the orthogonal nature of these mode shapes, the response of the structure to a traveling radial force wave with sinusoidal content at a given harmonic is due solely to the response of the mode shape with harmonic content of the same order. Introduction of impedance discontinuities to a shell yield complex mode shapes, which may be characterized by the summation of several harmonic components. These modes are no longer orthogonal in the presence of discontinuities, yielding harmonic content across various modal orders. As a result, a purely sinusoidal forcing function can excite several modes of the structure. Structural scattering as discussed in this paper refers to the phenomena in which a force wave at a given harmonic scatters into the response of modes with different harmonics. An experimental investigation into the harmonic scattering behavior of a shell due to mass discontinuities is presented in this paper. Knowledge of the key structural characteristics which influence scattering and their behavior will allow for a diagnostic tool when assessing the structural response of more complex cylindrical structures. Experimentally obtained data presented in this paper demonstrates some expected scattering characteristics of a cylindrical shell in the presence of periodically and aperiodically distributed masses. Some unique
Directory of Open Access Journals (Sweden)
Huaizhi Li
2016-08-01
Full Text Available High-speed counter-current chromatography (HSCCC has been successfully used for the separation of eight compounds from Chimonanthus praecox flowers. Firstly, the crude extract of Chimonanthus praecox flowers was dissolved in a two-phase solvent system composed of petroleum ether–ethyl acetate–methanol–H2O (5:5:3:7, v/v and divided into two parts: the upper phase (part I and the lower phase (part II. Then, HSCCC was applied to separate the phenolic acids from part I and part II, respectively. Considering the broad polarity range of target compounds in part I, a stepwise elution mode was established. Two optimal solvent systems of petroleum ether–ethyl acetate–methanol–H2O–formic acid (FA (5:5:3:7:0.02, 5:5:4.3:5.7:0.02, v/v were employed in this separation. Five phenylpropanoids and two flavonoids were successfully separated from 280 mg of part I, including 8.7 mg of 3,4-dihydroxy benzoic acid (a, 95.3% purity, 10.9 mg of protocatechualdehyde (b, 96.8% purity, 11.3 mg of p-coumaric acid (c, 98.9% purity, 12.2 mg of p-hydroxybenzaldehyde (d, 95.9% purity, 24.7 mg of quercetin (e, 97.3% purity, 33.8 mg of kaempferol (f, 96.8% purity, and 24.6 mg of 4-hydroxylcinnamic aldehyde (g, 98.0% purity. From 300 mg of part II, 65.7 mg of rutin (h, 98.2% purity, 7.5 mg of 3,4-dihydroxy benzoic acid (a, 77.4% purity, and 4.7 mg of protocatechualdehyde (b, 81.6% purity were obtained using the solvent system EtOAc–n-butanol (n-BuOH–FA–H2O (4:1:0.5:5, v/v. The structures of the eight pure compounds were confirmed by electrospray ionization-mass spectrometry (ESI-MS, 1H-NMR and 13C-NMR. To the best of our knowledge, compounds a–d and f were the first separated and reported from the Chimonanthus praecox flower extract.
Spacetime Meshing for Discontinuous Galerkin Methods
Thite, Shripad Vidyadhar
2008-01-01
Spacetime discontinuous Galerkin (SDG) finite element methods are used to solve such PDEs involving space and time variables arising from wave propagation phenomena in important applications in science and engineering. To support an accurate and efficient solution procedure using SDG methods and to exploit the flexibility of these methods, we give a meshing algorithm to construct an unstructured simplicial spacetime mesh over an arbitrary simplicial space domain. Our algorithm is the first spacetime meshing algorithm suitable for efficient solution of nonlinear phenomena in anisotropic media using novel discontinuous Galerkin finite element methods for implicit solutions directly in spacetime. Given a triangulated d-dimensional Euclidean space domain M (a simplicial complex) and initial conditions of the underlying hyperbolic spacetime PDE, we construct an unstructured simplicial mesh of the (d+1)-dimensional spacetime domain M x [0,infinity). Our algorithm uses a near-optimal number of spacetime elements, ea...
Archetypal oscillator for smooth and discontinuous dynamics.
Cao, Qingjie; Wiercigroch, Marian; Pavlovskaia, Ekaterina E; Grebogi, Celso; Thompson, J Michael T
2006-10-01
We propose an archetypal system to investigate transitions from smooth to discontinuous dynamics. In the smooth regime, the system bears significant similarities to the Duffing oscillator, exhibiting the standard dynamics governed by the hyperbolic structure associated with the stationary state of the double well. At the discontinuous limit, however, there is a substantial departure in the dynamics from the standard one. In particular, the velocity flow suffers a jump in crossing from one well to another, caused by the loss of local hyperbolicity due to the collapse of the stable and unstable manifolds of the stationary state. In the presence of damping and external excitation, the system has coexisting attractors and also a chaotic saddle which becomes a chaotic attractor when a smoothness parameter drops to zero. This attractor can bifurcate to a high-period periodic attractor or a chaotic sea with islands of quasiperiodic attractors depending on the strength of damping.
High-temperature discontinuously reinforced aluminum
Zedalis, M. S.; Bryant, J. D.; Gilman, P. S.; Das, S. K.
1991-08-01
High-temperature discontinuously reinforced aluminum (HTDRA) composites have been developed for elevated-temperature applications by incorporating SiC particulate reinforcement into a rapidly solidified, high-temperature Al-Fe-V-Si (alloy 8009) matrix. HTDRA combines the superior elevated-temperature strength, stability and corrosion resistance of the 8009 matrix with the excellent specific stiffness and abrasion resistance of the discontinuous SiC particulate reinforcement. On a specific stiffness basis, HTDRA is competitive with Ti-6-Al-4V and 17-4 PH stainless steel to temperatures approaching 480°C. Potential aerospace applications being considered for HTDRA include aircraft wing skins, missile bodies, and miscellaneous engine, spacecraft and hypersonic vehicle components.
Integer Discontinuity of Density Functional Theory
Mosquera, Martin A
2014-01-01
Density functional approximations to the exchange-correlation energy of Kohn-Sham theory, such as the local density approximation and generalized gradient approximations, lack the well-known integer discontinuity, a feature that is critical to describe molecular dissociation correctly. Moreover, standard approximations to the exchange-correlation energy also fail to yield the correct linear dependence of the ground-state energy on the number of electrons when this is a non-integer number obtained from the grand canonical ensemble statistics. We present a formal framework to restore the integer discontinuity of any density functional approximation. Our formalism derives from a formula for the exact energy functional and a new constrained search functional that recovers the linear dependence of the energy on the number of electrons.
Discontinued drugs 2011: endocrine and metabolic.
Colca, Jerry R
2012-11-01
This perspective summarizes key compounds from the endocrine and metabolic area that were discontinued during the calendar year 2011. Metabolic diseases continue to comprise some of the most important, but underserved areas of medical management. The candidates covered in this summary were primarily being developed for treatment of type 2 and type 1 diabetes, obesity and inflammatory gastrointestinal disease. Candidates were identified from a search by informahealthcare including data available on TreasureTrove. Discontinuation of programs during this period include older and newer projects but apparently all suffer from inability to provide timely evidence of clear benefit in clinical trials in the face of growing costs of development. There is a key need for targets that when modulated clearly affect the pathophysiology of the disease in way that is evident early in clinical trials.
Discontinuous Operation of Geothermal Heat Exchangers
Institute of Scientific and Technical Information of China (English)
方肇洪; 刁乃仁; 崔萍
2002-01-01
Ground-source heat pump (GSHP) systems for HVAC have aroused more and more interest in China in recent years because of their higher energy efficiency compared with conventional systems. The design and performance simulation of the geothermal heat exchangers is vital to the success of this technology. In GSHP systems, the load of the geothermal heat exchanger varies greatly and is usually discontinuous even during a heating or cooling season. This paper outlines a heat transfer model for geothermal heat exchangers. The model was used to study the influence of the discontinuous operation of the heat pumps on the performance of the geothermal heat exchangers. A simple and practical approach is presented for sizing the geothermal heat exchangers.
Mantle discontinuities beneath Izu-Bonin and the implications
Institute of Scientific and Technical Information of China (English)
臧绍先; 周元泽; 蒋志勇
2003-01-01
The SdP, pdP and sdP phases are picked up with the Nth root slant stack method from the digital waveform data recorded by the networks and arrays in USA, Germany and Switzerland for the earthquakes occurring beneath Izu-Bonin and Japan Sea. The mantle discontinuities and the effects of subducting slab on the 660 km and 410 km discontinuities are studied. It is found that there are mantle discontinuities existing at the depths of 170, 220, 300, 410, 660, 850 and 1150 km. Beneath Izu-Bonin, the 410 km discontinuity is elevated, while the 660 km discontinuity is depressed; for both discontinuities, there are regionalized differences. Beneath Japan Sea, however, there is no depth variation of the 410 km discontinuity, and the 660 km discontinuity is depressed without obvious effect of the subducting slab.
33 CFR 66.01-25 - Discontinuance and removal.
2010-07-01
... Discontinuance and removal. (a) No person, public body or instrumentality shall change, move or discontinue any... body or instrumentality establishing or maintaining such aids when so directed by the...
SENSITIVITY OF DARCY'S LAW TO DISCONTINUITIES
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
The authors investigate the sensitivity of hydrostatic pressure of flows through porous mediawith respect to the position of the soil layers. Indeed, these induce discontinuities of the porositypressure u and it leads to the computation of the derivative of u with respect to changes inThe analysis relies on a mixed formulation of the problem. Preliminary numerical simu-lations are given to illustrate the theory. An application to a simple inverse problem is also given.
Modeling Storm Surges Using Discontinuous Galerkin Methods
2016-06-01
discontinuous Galerkin solutions of the compressible Euler equations with applications to atmospheric simulations,” Journal of Computational Physics, vol...order continuous Galerkin methods were used for the SWE on a sphere [9]. In 2002, Giraldo et al. [10] introduced an efficient DG method for the SWE... hard time transitioning from changing bathymetry slopes causing distortions in the model to include extra line segments. The discrepancies caused us to
Metabolic effects of discontinuing growth hormone treatment
Cowan, F; Evans, W.; Gregory, J
1999-01-01
AIMS—To evaluate the effects of discontinuing growth hormone (GH) treatment on energy expenditure and body composition, which might help predict those most likely to benefit from early reintroduction of GH treatment in young adult life. METHODS—Body composition was calculated from skinfold thicknesses and dual energy x ray absorptometry (DXA). Resting metabolic rate (RMR) and whole body bone mineral content (BMC) were also measured. Measurements were made before stoppi...
Discontinuities, Feynman parameters and d-lines
Halliday, I G
1977-01-01
The calculation of asymptotic limits of Feynman diagrams using Feynman parameter techniques has developed a powerful and useful technology. A major gap in this armory has concerned the calculation of specific discontinuities of Feynman diagrams. The author remedies this gap and illustrates the new technique on a series of familiar situations. These include in the Regge limit, the ladder and the AFS diagrams, and the x approximately 1 deep inelastic electroproduction region. (4 refs).
Discontinuous precipitation in copper base alloys
Indian Academy of Sciences (India)
K T Kashyap
2009-08-01
Discontinuous precipitation (DP) is associated with grain boundary migration in the wake of which alternate plates of the precipitate and the depleted matrix form. Some copper base alloys show DP while others do not. In this paper the misfit strain parameter, , has been calculated and predicted that if 100 > ± 0.1, DP is observed. This criterion points to diffusional coherency strain theory to be the operative mechanism for DP.
Field Discontinuities and the Memory Effect
Tolish, Alexander; Wald, Robert
2017-01-01
The ``memory effect,'' a permanent change in the separation of test particles after the passage of a pulse of gravitational radiation, is a well-defined and fairly well-understood phenomenon in spacetimes with a notion of null infinity. However, many valid questions remain unanswered. For example, how do we define memory in the absence of null infinity? Or, does memory depend on the precise details of the radiation source or just on the source's asymptotic behavior? We believe that such questions are best answered using a simplified, distributional model of memory. If we consider linearized gravity on fixed background spacetimes, we can study the scattering of point particles, which radiate metric perturbations with sharp, step-function wave fronts. These steps correspond to derivative-of-delta-function discontinuities in the curvature, and according to the geodesic deviation equation, it is these discontinuities (and these alone) that contribute to permanent, finite changes in test particle separation-i.e., memory. Using this analysis of field discontinuities (as well as scalar and electromagnetic analogues of gravitational memory) we can isolate the physics of the memory effect from other, background phenomena.
Li, Ping
2017-03-22
In this paper, a discontinuous Galerkin time-domain (DGTD) method is developed to analyze the power-ground planes taking into account the decoupling capacitors. In the presence of decoupling capacitors, the whole physical system can be split into two subsystems: 1) the field subsystem that is governed by Maxwell\\'s equations that will be solved by the DGTD method, and 2) the circuit subsystem including the capacitor and its parasitic inductor and resistor, which is going to be characterized by the modified nodal analysis algorithm constructed circuit equations. With the aim to couple the two subsystems together, a lumped port is defined over a coaxial surface between the via barrel and the ground plane. To reach the coupling from the field to the circuit subsystem, a lumped voltage source calculated by the integration of electric field along the radial direction is introduced. On the other hand, to facilitate the coupling from the circuit to field subsystem, a lumped port current source calculated from the circuit equation is introduced, which serves as an impressed current source for the field subsystem. With these two auxiliary terms, a hybrid field-circuit matrix equation is established, which enables the field and circuit subsystems are solved in a synchronous scheme. Furthermore, the arbitrarily shaped antipads are considered by enforcing the proper wave port excitation using the magnetic surface current source derived from the antipads supported electric eigenmodes. In this way, the S-parameters corresponding to different modes can be conveniently extracted. To further improve the efficiency of the proposed algorithm in handling multiscale meshes, the local time-stepping marching scheme is applied. The proposed algorithm is verified by several representative examples.
Seismic wave propagation in fractured media: A discontinuous Galerkin approach
De Basabe, Jonás D.
2011-01-01
We formulate and implement a discontinuous Galekin method for elastic wave propagation that allows for discontinuities in the displacement field to simulate fractures or faults using the linear- slip model. We show numerical results using a 2D model with one linear- slip discontinuity and different frequencies. The results show a good agreement with analytic solutions. © 2011 Society of Exploration Geophysicists.
27 CFR 22.68 - Notice of permanent discontinuance.
2010-04-01
... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Notice of permanent discontinuance. 22.68 Section 22.68 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE... Permanent Discontinuance of Use of Tax-Free Alcohol § 22.68 Notice of permanent discontinuance. A...
Discontinuity effects in dynamically loaded tilting pad journal bearings
DEFF Research Database (Denmark)
Thomsen, Kim; Klit, Peder; Vølund, Anders
2011-01-01
This paper describes two discontinuity effects that can occur when modelling radial tilting pad bearings subjected to high dynamic loads. The first effect to be treated is a pressure build-up discontinuity effect. The second effect is a contact-related discontinuity that disappears when a contact...
Coupled dipole plasmonics of nanoantennas in discontinuous, complex dielectric environments
Forcherio, Gregory T.; Blake, Phillip; Seeram, Manoj; DeJarnette, Drew; Roper, D. Keith
2015-11-01
Two-dimensional metamaterials support both plasmonic and coupled lattice (Fano) resonant modes that together could enhance optoelectronics. Descriptions for plasmon excitation in Fano resonant lattices in non-vacuum environments typically use idealized, homogeneous matrices due to computational expense and limitations of common approaches. This work described both localized and coupled resonance activity of two-dimensional, square lattices of gold (Au) nanospheres (NS) in discontinuous, complex dielectric media using compact synthesis of discrete and coupled dipole approximations. This multi-scale approach supported attribution of experimentally observed spectral resonance energy and bandwidth to interactions between metal and dielectric substrate(s) supporting the lattices. Effective polarizabilities of single AuNS, either in vacuo or supported by glass and/or indium tin oxide (ITO) substrates, were obtained with discrete dipole approximation (DDA). This showed plasmon energy transport varied with type of substrate: glass increased scattering, while ITO increased absorption and energy confinement. Far-field lattice interactions between AuNS with/without substrates were computed by coupled dipole approximation (CDA) using effective polarizabilities. This showed glass enhanced diffractive features (e.g., coupled lattice resonance), while ITO supported plasmon modes. This compact, multiscale approach to describe metasurfaces in complex environments could accelerate their development and application.
Analysis on Common Mode Current of Single-Phase Grid-Connected PV System%单相光伏并网系统共模电流分析
Institute of Scientific and Technical Information of China (English)
杨秋霞; 高金玲; 荣雅君; 任玉艳
2011-01-01
Common mode current problem is very important to grid-connected photovoltaic (PV) system and in German standard DIN VDE 0126-1-1, the stipulations related to the common mode current are specified. When common mode current exceeds specified value, the connected PV generation system should be cut off within the stipulated time.Considering the importance of common mode current to the connection of photovoltaic generation to power grid, a common mode current is built. It is known throuth the analysis that common mode current is related to modulation technology and the position where the inductance locates. In allusion to above-mentioned features, a new single-phase grid-connected PV system that can suppress common mode current is designed.The designed system is a full-bridge single-phase gridconnected PV system with AC bypass circuit and in which inductances are symmetically arranged at both phase line and neutral line. Comparing with traditional full-bridge inverter systems adopting unipolar or bi-polar modulation technology,the structure of the proposed single-phase grid-connected PV system not only can eliminate common mode current produced in the grid-connected PV system, but also improve system efficiency and quality of current sent into power grid, thus the overall performance of the grid-connected PV system is improved. Results from theoretical analysis and simulation show that the proposed model and system are correct and available.%共模电流问题是光伏并网系统中的一个重要问题,德国DIN VDE 0126-1-1对共模电流做出了相关规定.当共模电流超过规定值时,系统必须在规定的时间内断开.考虑到共模电流在光伏并网系统中的重要性,建立了共模模型.通过分析可知,共模电流与调制技术和电感的安放位置相关.针对上述特点,设计了能够抑制共模电流的新型单相光伏并网系统,即带有交流旁路且电感对称分布在相线和中线上的全桥光伏并网系统.与传
Discontinuous Galerkin flood model formulation: Luxury or necessity?
Kesserwani, Georges; Wang, Yueling
2014-08-01
The finite volume Godunov-type flood model formulation is the most comprehensive amongst those currently employed for flood risk modeling. The local Discontinuous Galerkin method constitutes a more complex, rigorous, and extended local Godunov-type formulation. However, the practical merit associated with such an increase in the level of complexity of the formulation is yet to be decided. This work makes the case for a second-order Runge-Kutta Discontinuous Galerkin (RKDG2) formulation and contrasts it with the equivalently accurate finite volume (MUSCL) formulation, both of which solve the Shallow Water Equations (SWE) in two space dimensions. The numerical complexity of both formulations are presented and their capabilities are explored for wide-ranging diagnostic and real-scale tests, incorporating all challenging features relevant to flood inundation modeling. Our findings reveal that the extra complexity associated with the RKDG2 model pays off by providing higher-quality solution behavior on very coarse meshes and improved velocity predictions. The practical implication of this is that improved accuracy for flood modeling simulations will result when terrain data are limited or of a low resolution.
Mohorovicic discontinuity depth analysis beneath North Patagonian Massif
Gómez Dacal, M. L.; Tocho, C.; Aragón, E.
2013-05-01
models in the North Patagonian Massif area and in its West boundary but almost any difference in the other geographical limits. It is an interesting result and could be related with the isostatic compensation state of the area. References: Barzaghi R., Borghi A., Reguzzoni M., Sampietro D. Global Moho Estimate from GOCE Space-Wise Solution and a Local Application in the Mediterranean Area Bassin, C., Laske, G. and Masters, G., The Current Limits of Resolution for Surface Wave Tomography in North America, EOS Trans AGU, 81, F897, 2000. Feng M., Van der Lee S., Assumpçao M.. Upper mantle structure of South America from joint inersion of waveforms and fundamental mode group velocities of Rayleigh waves. Journal of Goephysical Research, vol. 112, B04312, doi:10.1029/2006JB004449,2007 Tassara A., A. Echaurren, 2011. Anatomy of the Chilean Subduction Zone: Three-dimensional density model upgraded and compared against global-scale models. Geophysical journal international, doi: 10.1111/j.1365-246X.2012.05397.x
Lipsey, Mark W.; Weiland, Christina; Yoshikawa, Hirokazu; Wilson, Sandra Jo; Hofer, Kerry G.
2015-01-01
Much of the currently available evidence on the causal effects of public prekindergarten programs on school readiness outcomes comes from studies that use a regression-discontinuity design (RDD) with the age cutoff to enter a program in a given year as the basis for assignment to treatment and control conditions. Because the RDD has high internal…
Nakagawa, Takahiro; Akera, Hiroshi; Suzuura, Hidekatsu
2005-06-01
Spatial variations of the electron temperature are calculated in the linear-response regime in a quantum Hall system with a potential discontinuity in the current direction. It is shown that the sign of the induced deviation of the electron temperature from the lattice temperature exhibits quantum oscillations.
Institute of Scientific and Technical Information of China (English)
肖甘
2013-01-01
本文以永磁同步电动机为基础,研究了直接滑模电流控制策略,该策略对参数变化以及外界干扰的鲁棒性较强,从而广泛应用于电气传动控制领域.设计了新颖的直接滑模电流控制器代替传统的PI电流控制器,并且采用了开关表查询方式加快了动态响应速度.最后基于TMS320DSP28335控制器对永磁同步电动机直接滑模电流控制控制系统进行实验验证,结果表明所设计的控制器动态响应较快,抗干扰能力较强.%This paper researched on direct sliding mode current control of a permanent magnet synchronous machine.Due to the robustness to parameters variations and external disturbances,sliding mode controllers were widely used for the control of electrical drives.A novel direct sliding mode current controller was designed to substitute the traditional PI current controller,and switch table was used to speed up the dynamic response.As a result,the experiment of permanent magnet synchronous machine direct sliding mode current control system based on TMS320DSP28335 controller was finished.The experimental results illustrate this designed controller has faster dynamic response and stronger anti-interference ability.
A.B. Chattopadhyay; Sunil Thomas
2014-01-01
Modeling of synchronous motor plays a dominant role in designing complicated drive system for different applications, especially large blower fans etc for steel industries. As synchronous motor has no inherent starting torque generally it is started as an induction motor with the help of a damper winding and it pulls into synchronism under certain conditions. The present paper exactly concentrates on this particular zone of transition from induction motor to synchronous motor mode for a curre...
A.B. Chattopadhyay; Sunil Thomas
2014-01-01
Modeling of synchronous motor plays a dominant role in designing complicated drive system for different applications, especially large blower fans etc., for steel industries. As synchronous motor has no inherent starting torque generally it is started as an induction motor with the help of a damper winding and it pulls into synchronism under certain conditions. The present study exactly concentrates on this particular zone of transition from induction motor to synchronous motor mode for a cur...
Larsson, Anders; Gustavsson, Johan S.
The only active transverse mode in a truly single-mode VCSEL is the fundamental mode with a near Gaussian field distribution. A single-mode VCSEL produces a light beam of higher spectral purity, higher degree of coherence and lower divergence than a multimode VCSEL and the beam can be more precisely shaped and focused to a smaller spot. Such beam properties are required in many applications. In this chapter, after discussing applications of single-mode VCSELs, we introduce the basics of fields and modes in VCSELs and review designs implemented for single-mode emission from VCSELs in different materials and at different wavelengths. This includes VCSELs that are inherently single-mode as well as inherently multimode VCSELs where higher-order modes are suppressed by mode selective gain or loss. In each case we present the current state-of-the-art and discuss pros and cons. At the end, a specific example with experimental results is provided and, as a summary, the most promising designs based on current technologies are identified.
Directory of Open Access Journals (Sweden)
Yue Sun
2016-01-01
Full Text Available A novel coupling scheme is presented to combine the discontinuous deformation analysis (DDA and the interior penalty Galerkin (IPG method for the modeling of contacts. The simultaneous equilibrium equations are assembled in a mixed strategy, where the entries are derived from both discontinuous Galerkin variational formulations and the strain energies of DDA contact springs. The contact algorithms of the DDA are generalized for element contacts, including contact detection criteria, open-close iteration, and contact submatrices. Three representative numerical examples on contact problems are conducted. Comparative investigations on the results obtained by our coupling scheme, ANSYS, and analytical theories demonstrate the accuracy and effectiveness of the proposed method.
Discontinuous deformation analysis based on complementary theory
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
The contact between blocks is treated by the open-close iteration in the conventional discontinuous deformation analysis (DDA),which needs to introduce spurious springs between two blocks in contact and to assume the normal stiffness and the tangential stiffness (the penalty factors). Unreasonable values of stiffness would result in numerical problems. To avoid the penalty factors and the open-close iteration,we reformulate the DDA as a mixed complementary problem (MiCP) and then choose the path Newton method (PNM) to solve the problem. Some examples including those originally designed by Shi are reanalyzed,which proves feasibility of the proposed procedure.
Singularity and dynamics on discontinuous vector fields
Luo, Albert CJ
2006-01-01
This book discussed fundamental problems in dynamics, which extensively exist in engineering, natural and social sciences. The book presented a basic theory for the interactions among many dynamical systems and for a system whose motions are constrained naturally or artificially. The methodology and techniques presented in this book are applicable to discontinuous dynamical systems in physics, engineering and control. In addition, they may provide useful tools to solve non-traditional dynamics in biology, stock market and internet network et al, which cannot be easily solved by the traditional
Discontinuation of the Bulletin's menu page
Publications Section
2005-01-01
The menus of the various CERN restaurants will no longer be published in the Bulletin as of Monday 4 April (issue No. 14/2005). The menu pages are being discontinued both as a savings measure and due to the low level of interest in this section of the Bulletin. The most recent survey of Bulletin readers showed that only 13% of the people questioned regularly read the menu section, compared to between 40% and 85% in the case of the other sections. Publications Section SG/CO Tel. 79971
Discontinuation of the Bulletin's menu page
Publications Section
2005-01-01
The menus of the various CERN restaurants will no longer be published in the Bulletin as of Monday 4 April (issue No. 14/2005). The menu pages are being discontinued both as a savings measure and due to the low level of interest in this section of the Bulletin. The most recent survey of Bulletin readers showed that only 13% of the people questioned regularly read the menu section, compared to between 40% and 85% in the case of the other sections. Publications Section DSU-CO Tel. 79971
A Level Set Discontinuous Galerkin Method for Free Surface Flows - and Water-Wave Modeling
DEFF Research Database (Denmark)
Grooss, Jesper
2005-01-01
We present a discontinuous Galerkin method on a fully unstructured grid for the modeling of unsteady incompressible fluid flows with free surfaces. The surface is modeled by a level set technique. We describe the discontinuous Galerkin method in general, and its application to the flow equations....... The deferred correction method is applied on the fluid flow equations and show good results in periodic domains. We describe the design of a level set method for the free surface modeling. The level set utilize the high order accurate discontinuous Galerkin method fully and represent smooth surfaces very...... equations in time are discussed. We investigate theory of di erential algebraic equations, and connect the theory to current methods for solving the unsteady fluid flow equations. We explore the use of a semi-implicit spectral deferred correction method having potential to achieve high temporal order...
Discontinued drugs in 2012: endocrine and metabolic.
Colca, Jerry R
2013-10-01
This perspective summarizes 42 drug projects in the general areas of endocrine and metabolic diseases that were reported discontinued during 2012. These programs include development projects against diabetes, metabolic complications (including kidney and liver disease), as well as projects that can be described as approaches to treatment of obesity/anorexia, lipids and various inflammatory diseases. Candidates were identified from a search by Informa Healthcare including data available on TreasureTrove as provided by EOID. Additional information was sought using Google, PubMed, HighWire and ClinicalTrials.gov. The summary of discontinued projects in this area for 2012 provides little in the way of specific guidance especially since details of the fate of most projects are often lacking. Nonetheless, it seems clear that none of these projects has hit upon the key aspects of the pathophysiology of the disorders that they were intended to treat, and the most likely cause of failure is the lack of the ability to produce compelling evidence to support the respective business case in the sense of efficacy/potential therapeutic profile.
Rock discontinuity surface roughness variation with scale
Bitenc, Maja; Kieffer, D. Scott; Khoshelham, Kourosh
2017-04-01
ABSTRACT: Rock discontinuity surface roughness refers to local departures of the discontinuity surface from planarity and is an important factor influencing the shear resistance. In practice, the Joint Roughness Coefficient (JRC) roughness parameter is commonly relied upon and input to a shear strength criterion such as developed by Barton and Choubey [1977]. The estimation of roughness by JRC is hindered firstly by the subjective nature of visually comparing the joint profile to the ten standard profiles. Secondly, when correlating the standard JRC values and other objective measures of roughness, the roughness idealization is limited to a 2D profile of 10 cm length. With the advance of measuring technologies that provide accurate and high resolution 3D data of surface topography on different scales, new 3D roughness parameters have been developed. A desirable parameter is one that describes rock surface geometry as well as the direction and scale dependency of roughness. In this research a 3D roughness parameter developed by Grasselli [2001] and adapted by Tatone and Grasselli [2009] is adopted. It characterizes surface topography as the cumulative distribution of local apparent inclination of asperities with respect to the shear strength (analysis) direction. Thus, the 3D roughness parameter describes the roughness amplitude and anisotropy (direction dependency), but does not capture the scale properties. In different studies the roughness scale-dependency has been attributed to data resolution or size of the surface joint (see a summary of researches in [Tatone and Grasselli, 2012]). Clearly, the lower resolution results in lower roughness. On the other hand, have the investigations of surface size effect produced conflicting results. While some studies have shown a decrease in roughness with increasing discontinuity size (negative scale effect), others have shown the existence of positive scale effects, or both positive and negative scale effects. We
Directory of Open Access Journals (Sweden)
Mahumud RA
2015-01-01
used the pill (OR =0.72 and injectable contraception users (OR =0.60, had small family size (OR =0.49, lived in a rural community (OR =1.65, and who were less educated (OR =1.55.Conclusion: Contraceptive discontinuation may reflect an association among less education, currently married, and smaller family size. Awareness of contraceptive methods can decrease the burden of unplanned pregnancies and thus progresses the family planning program. Keywords: prevalence, contraceptive discontinuation, switching, BDHS, odds ratio, logistic regression
Lloyd, Nicholas S; Sadekov, Aleksey Yu; Misra, Sambuddha
2017-10-09
Boron isotope ratios (δ(11) B values) are used as a proxy for seawater paleo-pH, amongst several other applications. The analytical precision can be limited by the detection of low intensity ion beams from limited sample amounts. High-gain amplifiers offer improvements in signal/noise ratio and can be used to increase measurement precision and reduce sample amounts. 10(13) ohm amplifier technology has previously been applied to several radiogenic systems, but has thus far not been applied to non-traditional stable isotopes. Here we apply 10(13) ohm amplifier technology for the measurement of boron isotope ratios using solution mode MC-ICP-MS and laser ablation mode (LA-) MC-ICP-MS techniques. Precision is shown for reference materials as well as for low-volume foraminifera samples. The baseline uncertainty for a 0.1 pA (10) B ion beam is reduced to ohm amplifier technology is demonstrated to offer advantages for the determination of δ(11) B values by both MC-ICP-MS and LA-MC-ICP-MS for small samples of biogenic carbonates, such as foraminifera shells. 10(13) ohm amplifier technology will also be of benefit to other non-traditional stable isotope measurements. This article is protected by copyright. All rights reserved.
Schatzberg, A F; Haddad, P; Kaplan, E M; Lejoyeux, M; Rosenbaum, J F; Young, A H; Zajecka, J
1997-01-01
Adverse events following discontinuation from serotonin reuptake inhibitors (SRIs) are being reported in the literature with increasing frequency; the frequency and severity of these symptoms appear to vary according to the half-life of the SRI, e.g., the incidence appears higher with the shorter half-life agents than with fluoxetine, which has an extended half-life. Yet, there have been no systematic studies of the phenomenon to date. Therefore, a group of experts convened in Phoenix, Arizona, to develop a clear description or definition of the phenomenon based on these reports. The SRI discontinuation syndrome, referred to as "withdrawal symptoms" in many anecdotal case reports, is distinctly different from the classic withdrawal syndrome associated with alcohol and barbiturates. Anti-depressants are not associated with dependence or drug-seeking behavior. SRI discontinuation symptoms tend to be short-lived and self-limiting, but can be troublesome. They may emerge when an SRI is abruptly discontinued, when doses are missed, and less frequently, during dosage reduction. In addition, the symptoms are not attributable to any other cause and can be reversed when the original agent is reinstituted, or one that is pharmacologically similar is substituted. SRI discontinuation symptoms, in most cases, may be minimized by slowly tapering antidepressant therapy, but there have been several case reports where symptoms occurred consistently even through repeated attempts to taper therapy. Physical symptoms include problems with balance, gastrointestinal and flu-like symptoms, and sensory and sleep disturbances. Psychological symptoms include anxiety and/or agitation, crying spells, and irritability. Further analyses of data bases and clinical studies are needed to define this proposed syndrome more clearly.
Homentcovschi, Dorel; Miles, Ronald N.
2010-01-01
The paper gives a new method for analyzing planar discontinuities in rectangular waveguides. The method consists of a re-expansion of the normal modes in the two ducts at the junction plane into a system of functions accounting for the velocity singularities at the corner points. As the new expansion has an exponential convergence, only a few terms have to be considered for obtaining the solution of most practical problems. To see how the method works some closed form solutions, obtained by the conformal mapping method, are used to discuss the convergence of the re-expanded series when the number of retained terms increases. The equivalent impedance accounting for nonplanar waves into a plane-wave analysis is determined. Finally, the paper yields the scattering matrix which describes the coupling of arbitrary modes at each side of the discontinuity valid in the case of many propagating modes in both parts of the duct. PMID:20707432
反激式恒流一次侧控制模式的研究%Research of Flyback Converter Constant Current Primary Control Mode
Institute of Scientific and Technical Information of China (English)
赵子龙; 陈弯; 陈永真
2015-01-01
The flyback converter output constant current characteristic has important applications in many occasions, such as constant pressure constant current charger, the LED constant current drive, etc. The method of secondary side current feedback can increase the cost and complexity of the circuit. The primary side adjustment method is studied to control the output constant current in this paper. Output current information is obtained from the primary side of transformer, avoiding the secondary side current sampling circuit and photoelectric coupler components, reducing the complexity of the circuit, improving the efficiency of the circuit. The experiment is done to acquire the experimental waveforms and data with the primary side regulation, and results verify the advanced nature of the primary side regulation.%反激式变换器输出恒流特性在许多场合，如恒压恒流充电器、LED恒流驱动器等有着重要的应用。输出恒流采用二次侧电流反馈的方法会增加电路的成本和复杂性。通过采用一次侧调节的方法来控制输出恒流，在变压器的一次侧检测输出电流的信息，避免了二次侧电流采样电路和光电耦合器等元器件，减小了电路的复杂性，提高了电路的效率。通过实验得到采用一次侧调节的实验波形和数据，验证了一次侧调节的先进性。
[Discontinuation of depression treatment from the perspective of suicide prevention].
Cho, Yoshinori
2012-01-01
It is assumed that discontinuation of treatment for depression may increase the risk of suicide. A population-based register study in Denmark did not find a lower risk among people over age 50 who followed treatment in comparison with those who discontinued treatment with antidepressants at an early stage. This result, however, does not allow us to think superficially that early discontinuation of treatment does not increase the risk of suicide. It is because the study has limitations without information of such as psychiatric diagnoses, severity of the depressed state, and reasons of discontinuation. It is safe for clinicians to aim at preventing discontinuation of treatment. Particularly, in Japan and South Korea where there is a sociocultural climate of tolerability for suicide, suicide can occur in milder depressed state and discontinuation of treatment should be taken more seriously than in Western countries.
Quantitative identification of technological discontinuities using simulation modeling
Park, Hyunseok
2016-01-01
The aim of this paper is to develop and test metrics to quantitatively identify technological discontinuities in a knowledge network. We developed five metrics based on innovation theories and tested the metrics by a simulation model-based knowledge network and hypothetically designed discontinuity. The designed discontinuity is modeled as a node which combines two different knowledge streams and whose knowledge is dominantly persistent in the knowledge network. The performances of the proposed metrics were evaluated by how well the metrics can distinguish the designed discontinuity from other nodes on the knowledge network. The simulation results show that the persistence times # of converging main paths provides the best performance in identifying the designed discontinuity: the designed discontinuity was identified as one of the top 3 patents with 96~99% probability by Metric 5 and it is, according to the size of a domain, 12~34% better than the performance of the second best metric. Beyond the simulation ...
Evaluating Discontinuities in Complex Systems: Toward Quantitative Measures of Resilience
Directory of Open Access Journals (Sweden)
Craig Stow
2007-06-01
Full Text Available The textural discontinuity hypothesis (TDH is based on the observation that animal body mass distributions exhibit discontinuities that may reflect the texture of the landscape available for exploitation. This idea has been extended to other complex systems, hinting that the identification and quantification of discontinuities in the distributions of appropriate variables may provide clues to emergent system properties such as resilience. We propose a discontinuity index, based on the vector norm of the full assemblage of observed discontinuities, as a means to quantify and compare this characteristic among systems. We also evaluate four methods to identify the number and location of the most prominent discontinuities. Although results of the four methods are similar, they are not identical, and we conclude that this problem is best addressed with a consistent operationally defined approach in an adaptive inference framework.
Discontinuous Mixed Covolume Methods for Linear Parabolic Integrodifferential Problems
Directory of Open Access Journals (Sweden)
Ailing Zhu
2014-01-01
Full Text Available The semidiscrete and fully discrete discontinuous mixed covolume schemes for the linear parabolic integrodifferential problems on triangular meshes are proposed. The error analysis of the semidiscrete and fully discrete discontinuous mixed covolume scheme is presented and the optimal order error estimate in discontinuous H(div and first-order error estimate in L2 are obtained with the lowest order Raviart-Thomas mixed element space.
On stability of discontinuous systems via vector Lyapunov functions
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
This paper deals with the stability of systems with discontinuous righthand side (with solutions in Filippov's sense) via locally Lipschitz continuous and regular vector Lyapunov functions. A new type of "set-valued derivative" of vector Lyapunov functions is introduced, some generalized comparison principles on dis(c)ontinuous systems are shown. Furthermore, Lyapunov stability theory is developed for a class of discontinuous systems based on locally Lipschitz continuous and regular vector Lyapunov functions.
Discontinuation of denosumab and associated fracture incidence
DEFF Research Database (Denmark)
Brown, Jacques P; Roux, Christian; Törring, Ove;
2012-01-01
Osteoporosis is a chronic disease and requires long-term treatment with pharmacologic therapy to ensure sustained anti-fracture benefit. Denosumab reduced the risk for new vertebral, nonvertebral, and hip fractures over 36 months in the FREEDOM trial. While discontinuation of denosumab has been...... associated with transient increases in bone remodeling and declines in bone mineral density (BMD), the effect on fracture risk during treatment cessation is not as well characterized. To understand the fracture incidence between treatment groups after cessation of investigational product, we evaluated...... of 797 subjects (470 placebo, 327 denosumab), who were evaluable during the off-treatment period, showed similar baseline characteristics for age, prevalent fracture, and lumbar spine and total hip BMD T-scores. During treatment, more placebo-treated subjects as compared with denosumab-treated subjects...
Discontinuous Galerkin Methods with Trefftz Approximation
Kretzschmar, Fritz; Tsukerman, Igor; Weiland, Thomas
2013-01-01
We present a novel Discontinuous Galerkin Finite Element Method for wave propagation problems. The method employs space-time Trefftz-type basis functions that satisfy the underlying partial differential equations and the respective interface boundary conditions exactly in an element-wise fashion. The basis functions can be of arbitrary high order, and we demonstrate spectral convergence in the $\\Lebesgue_2$-norm. In this context, spectral convergence is obtained with respect to the approximation error in the entire space-time domain of interest, i.e. in space and time simultaneously. Formulating the approximation in terms of a space-time Trefftz basis makes high order time integration an inherent property of the method and clearly sets it apart from methods, that employ a high order approximation in space only.
RURAL TOURISM IN ROMANIA - EVOLUTIONS AND DISCONTINUITIES
Directory of Open Access Journals (Sweden)
Silviu COSTACHIE
2011-12-01
Full Text Available This paper analyzes the evolution of rural tourism since the early '70s, the time of onset, and indicates the discontinuity recorded especially after 1989 until the brink of the preparation for Romania's joining the European Union and the present state, one far behind the countries with extremely high degree of urbanization and industrialization, probably as a result of a lack of strategy for this form of tourism in which the beneficiary is the Ministry of Tourism, as the health tourism and ecotourism have recently had. The location of many villages in areas of outstanding natural landscapes, the richness and variety of cultural heritage that endows them, are issues related to an increased tourism potential that can be capitalized and those unique tourism products that can not be seen, admired and offered by other countries.
Interfaces of the discontinuation of breastfeeding
Directory of Open Access Journals (Sweden)
Mirna Albuquerque Frota
2016-06-01
Full Text Available The objective was to identify conditions for the discontinuation of exclusive breastfeeding. This is a qualitative study developed in a Primary Health Care Unit (PHCU in Fortaleza, Ceará, Brazil. It included 20 mothers of children aged 0-6 months old who were breastfeeding. The reports evidenced three categories: Guidance received during prenatal care; Meanings of breastfeeding; Determinants of early weaning. It can be concluded that part of the determinants of early weaning is in the building of or failure to build knowledge about breastfeeding. Cultural concepts or myths are inadequate and socially reproduced due to failure, on the part of health professionals who assist expectant mothers during prenatal care or those who assist postpartum women, to deconstruct them.
Discontinuous Galerkin Methods for Turbulence Simulation
Collis, S. Scott
2002-01-01
A discontinuous Galerkin (DG) method is formulated, implemented, and tested for simulation of compressible turbulent flows. The method is applied to turbulent channel flow at low Reynolds number, where it is found to successfully predict low-order statistics with fewer degrees of freedom than traditional numerical methods. This reduction is achieved by utilizing local hp-refinement such that the computational grid is refined simultaneously in all three spatial coordinates with decreasing distance from the wall. Another advantage of DG is that Dirichlet boundary conditions can be enforced weakly through integrals of the numerical fluxes. Both for a model advection-diffusion problem and for turbulent channel flow, weak enforcement of wall boundaries is found to improve results at low resolution. Such weak boundary conditions may play a pivotal role in wall modeling for large-eddy simulation.
Discontinuity and complexity in nonlinear physical systems
Baleanu, Dumitru; Luo, Albert
2014-01-01
This unique book explores recent developments in experimental research in this broad field, organized in four distinct sections. Part I introduces the reader to the fractional dynamics and Lie group analysis for nonlinear partial differential equations. Part II covers chaos and complexity in nonlinear Hamiltonian systems, important to understand the resonance interactions in nonlinear dynamical systems, such as Tsunami waves and wildfire propagations; as well as Lev flights in chaotic trajectories, dynamical system synchronization and DNA information complexity analysis. Part III examines chaos and periodic motions in discontinuous dynamical systems, extensively present in a range of systems, including piecewise linear systems, vibro-impact systems and drilling systems in engineering. And in Part IV, engineering and financial nonlinearity are discussed. The mechanism of shock wave with saddle-node bifurcation and rotating disk stability will be presented, and the financial nonlinear models will be discussed....
Kamal-Bahl, Sachin J; Burke, Thomas; Watson, Douglas; Wentworth, Chuck
2007-02-15
Although several lipid-modifying drug (LMD) treatments and strategies are available to successfully manage patients at risk for cardiovascular events, the benefits of drug treatment can be realized only if these therapies are continued on a long-term basis. Previous observational studies examining rates of discontinuation with LMDs are not generalizable to current clinical practice in the United States. In this study, the discontinuation of newly initiated LMD classes in recent clinical practice was compared in a geographically diverse, commercially insured United States population. Administrative claims from the Ingenix Lab/Rx Database were used to identify patients aged >or=20 years who were newly prescribed statins, extended-release niacin, fibrates, bile acid sequestrants, or ezetimibe from January 1, 2001, to June 30, 2003. An LMD class was considered discontinued if a patient did not receive a prescription from the same LMD class within 180 days of the most recent prescription expiration date. The median time to discontinuation was 8.2 months in the bile acid sequestrant group, followed by 12 months in the extended-release niacin group, 17.4 months in the fibrate group, and 27.5 months in the statin group. By the end of 1 year, the adjusted cumulative incidence of discontinuation was 68.3% in bile acid sequestrant users, 55.4% in extended-release niacin users, 39.9% in fibrate users, 33.0% in ezetimibe users, and 28.9% in statin users (p LMD classes vs statins). In conclusion, despite the changes in lipid treatment paradigms and the importance of long-term lipid therapy, this study found high discontinuation rates of LMD classes in recent United States clinical practice.
Bifurcation behaviours of peak current controlled PFC boost converter
Institute of Scientific and Technical Information of China (English)
Ren Hai-Peng; Liu Ding
2005-01-01
Bifurcation behaviours of the peak current controlled power-factor-correction (PFC) boost converter, including fast-scale instability and low-frequency bifurcation, are investigated in this paper. Conventionally, the PFC converter is analysed in continuous conduction mode (CCM). This prevents us from recognizing the overall dynamics of the converter. It has been pointed out that the discontinuous conduction mode (DCM) can occur in the PFC boost converter, especially in the light load condition. Therefore, the DCM model is employed to analyse the PFC converter to cover the possible DCM operation. By this way, the low-frequency bifurcation diagram is derived, which makes the route from period-double bifurcation to chaos clear. The bifurcation diagrams versus the load resistance and the output capacitance also indicate the stable operation boundary of the converter, which is useful for converter design.
DISCONTINUOUS SOLUTIONS IN L∞ FOR HAMILTON-JACOBI EQUATIONS
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
An approach is introduced to construct global discontinuous solutions in L∞ for Hamilton Jacobi equations. This approach allows the initial data only in L∞ and applies to the equations with nonconvex Hamiltonians. The profit functions are introduced to formulate the notion of discontinuous solutions in L. The existence of global discontinuous solutions in L∞ is established. These solutions in L∞ coincide with the viscosity solutions and the minimax solutions, provided that the initial data are continuous. A prototypical equation is analyzed to examine the L∞ stability of our L∞ solutions. The analysis also shows that global discontinuous solutions are determined by the topology in which the initial data are approximated.
DEFF Research Database (Denmark)
Tang, Y.; Yao, W.; Blaabjerg, Frede
2015-01-01
In single-phase uninterruptible power supply (UPS) applications, it is well known that the AC side instantaneous power is not constant by nature. The resulting input current from the DC source side will inevitably contain low frequency ripple components that may largely deteriorate the system...
Directory of Open Access Journals (Sweden)
Soraya Omardien
2016-10-01
Full Text Available Antimicrobial peptides (AMPs have been proposed as a novel class of antimicrobials that could aid the fight against antibiotic resistant bacteria. The mode of action of AMPs as acting on the bacterial cytoplasmic membrane has often been presented as an enigma and there are doubts whether the membrane is the sole target of AMPs. Progress has been made in clarifying the possible targets of these peptides, which is reported in this review with as focus gram-positive vegetative cells and spores. Numerical estimates are discussed to evaluate the possibility that targets, other than the membrane, could play a role in susceptibility to AMPs. Concerns about possible resistance that bacteria might develop to AMPs are addressed. Proteomics, transcriptomics and other molecular techniques are reviewed in the context of explaining the response of bacteria to the presence of AMPs and to predict what resistance strategies might be. Emergent mechanisms are cell envelope stress responses as well as enzymes able to degrade and/or specifically bind (and thus inactivate AMPs. Further studies are needed to address the broadness of the AMP resistance and stress responses observed.
Omardien, Soraya; Brul, Stanley; Zaat, Sebastian A. J.
2016-01-01
Antimicrobial peptides (AMPs) have been proposed as a novel class of antimicrobials that could aid the fight against antibiotic resistant bacteria. The mode of action of AMPs as acting on the bacterial cytoplasmic membrane has often been presented as an enigma and there are doubts whether the membrane is the sole target of AMPs. Progress has been made in clarifying the possible targets of these peptides, which is reported in this review with as focus gram-positive vegetative cells and spores. Numerical estimates are discussed to evaluate the possibility that targets, other than the membrane, could play a role in susceptibility to AMPs. Concerns about possible resistance that bacteria might develop to AMPs are addressed. Proteomics, transcriptomics, and other molecular techniques are reviewed in the context of explaining the response of bacteria to the presence of AMPs and to predict what resistance strategies might be. Emergent mechanisms are cell envelope stress responses as well as enzymes able to degrade and/or specifically bind (and thus inactivate) AMPs. Further studies are needed to address the broadness of the AMP resistance and stress responses observed.
High order discontinuous Galerkin discretizations with discontinuity resolution within the cell
Ekaterinaris, John; Panourgias, Konstantinos
2016-11-01
The nonlinear filter of Yee et al. and used for low dissipative well-balanced high order accurate finite-difference schemes is adapted to the finite element context of discontinuous Galerkin (DG) discretizations. The performance of the proposed nonlinear filter for DG discretizations is demonstrated for different orders of expansions for one- and multi-dimensional problems with exact solutions. It is shown that for higher order discretizations discontinuity resolution within the cell is achieved and the design order of accuracy is preserved. The filter is applied for inviscid and viscous flow test problems including strong shocks interactions to demonstrate that the proposed dissipative mechanism for DG discretizations yields superior results compared to the results obtained with the TVB limiter and high-order hierarchical limiting. The proposed approach is suitable for p-adaptivity in order to locally enhance resolution of three-dimensional flow simulations.
Fluxon modes in superconducting multilayers
DEFF Research Database (Denmark)
Pedersen, Niels Falsig; Madsen, Søren Peder
2004-01-01
We show how to construct fluxon modes from plasma modes in the inductively coupled stacked Josephson junctions, and consider some special cases of these fluxon modes analytically. In some cases we can find exact analytical solutions when we choose the bias current in a special way. We also consid...
Modelling and analysis of current-programmed ac/dc converters
Tymerski, R. P. E.; Daly, K. C.
1985-03-01
Current-programmed dc/dc converters operating at a fixed switching frequency are analyzed using state-space averaged modeling. For converters operating in the continuous conduction mode, general closed form expressions that describe the dynamic ac small signal characteristics of the converter are obtained. A reduced order model is used to derive the control current input-to-output voltage, audio susceptibility and output impedance small signal ac transfer functions for the ideal buck, boost, and buck-boost converters operating in the continuous conduction model. It is shown that state-space averaging can correctly predict instability on the buck converter. Current-programmed converters operating in the discontinuous conduction mode are addressed, showing that the transfer functions are represented by a finite pole and a zero at infinity. Instability is predicted for the buck converter when an external ramp is omitted and the output-to-input voltage ratio is greater than or equal to two-thirds.
Shang, J.; Hencher, S. R.; West, L. J.
2016-11-01
Geological discontinuities have a controlling influence for many rock-engineering projects in terms of strength, deformability and permeability, but their characterisation is often very difficult. Whilst discontinuities are often modelled as lacking any strength, in many rock masses visible rock discontinuities are only incipient and have tensile strength that may approach and can even exceed that of the parent rock. This fact is of high importance for realistic rock mass characterisation but is generally ignored. It is argued that current ISRM and other standards for rock mass characterisation, as well as rock mass classification schemes such as RMR and Q, do not allow adequately for the incipient nature of many rock fractures or their geological variability and need to be revised, at least conceptually. This paper addresses the issue of the tensile strength of incipient discontinuities in rock and presents results from a laboratory test programme to quantify this parameter. Rock samples containing visible, natural incipient discontinuities including joints, bedding, and mineral veins have been tested in direct tension. It has been confirmed that such discontinuities can have high tensile strength, approaching that of the parent rock. Others are, of course, far weaker. The tested geological discontinuities all exhibited brittle failure at axial strain less than 0.5 % under direct tension conditions. Three factors contributing to the tensile strength of incipient rock discontinuities have been investigated and characterised. A distinction is made between sections of discontinuity that are only partially developed, sections of discontinuity that have been locally weathered leaving localised residual rock bridges and sections that have been `healed' through secondary cementation. Tests on bedding surfaces within sandstone showed that tensile strength of adjacent incipient bedding can vary considerably. In this particular series of tests, values of tensile strength
Directory of Open Access Journals (Sweden)
Yanzhao He
2017-02-01
Full Text Available The start-up current control of the high-speed brushless DC (HS-BLDC motor is a challenging research topic. To effectively control the start-up current of the sensorless HS-BLDC motor, an adaptive control method is proposed based on the adaptive neural network (ANN inverse system and the two degrees of freedom (2-DOF internal model controller (IMC. The HS-BLDC motor is identified by the online least squares support vector machine (OLS-SVM algorithm to regulate the ANN inverse controller parameters in real time. A pseudo linear system is developed by introducing the constructed real-time inverse system into the original HS-BLDC motor system. Based on the characteristics of the pseudo linear system, an extra closed-loop feedback control strategy based on the 2-DOF IMC is proposed to improve the transient response performance and enhance the stability of the control system. The simulation and experimental results show that the proposed control method is effective and perfect start-up current tracking performance is achieved.
Panourgias, Konstantinos T.; Ekaterinaris, John A.
2016-12-01
The nonlinear filter introduced by Yee et al. (1999) [27] and extensively used in the development of low dissipative well-balanced high order accurate finite-difference schemes is adapted to the finite element context of discontinuous Galerkin (DG) discretizations. The filter operator is constructed in the canonical computational domain for the standard cubical element where it is applied to the computed conservative variables in a direction per direction basis. Filtering becomes possible for all element types in unstructured meshes using collapsed coordinate transformations. The performance of the proposed nonlinear filter for DG discretizations is demonstrated and evaluated for different orders of expansions for one-dimensional and multidimensional problems with exact solutions. It is shown that for higher order discretizations discontinuity resolution within the cell is achieved and the design order of accuracy is preserved. The filter is applied for a number of standard inviscid flow test problems including strong shocks interactions to demonstrate that the proposed dissipative mechanism for DG discretizations yields superior results compared to the results obtained with the total variation bounded (TVB) limiter and high-order hierarchical limiting. The proposed approach is suitable for p-adaptivity in order to locally enhance resolution of three-dimensional flow simulations that include discontinuities and complex flow features.
Energy Technology Data Exchange (ETDEWEB)
Basu, S. [Nuclear Regulatory Commission, Washington, DC (United States); Ginsberg, T. [Brookhaven National Lab., Upton, NY (United States)
1996-08-01
This report summarizes the review and evaluation by experts of the current understanding of the molten fuel-coolant interaction (FCI) issues covering the complete spectrum of interactions, i.e., from mild quenching to very energetic interactions including those that could lead to the alpha-mode containment failure. Of the eleven experts polled, all but two concluded that the alpha-mode failure issue was resolved from a risk perspective, meaning that this mode of failure is of very low probability, that it is of little or no significance to the overall risk from a nuclear power plant, and that any further reduction in residual uncertainties is not likely to change the probability in an appreciable manner. To a lesser degree, discussions also took place on the broader FCI issues such as mild quenching of core melt during non-explosive FCI, and shock loading of lower head and ex-vessel support structures arising from explosive localized FCIs. These latter issues are relevant with regard to determining the efficacy of certain accident management strategies for operating reactors as well as for advanced light water reactors. The experts reviewed the status of understanding of the FCI phenomena in the context of these broader issues, identified residual uncertainties in the understanding, and recommended future research (both experimental and analytical) to reduce the uncertainties.
Current Sensorless Control Algorithm for Single-Phase Three-Level NPC Inverter
Directory of Open Access Journals (Sweden)
Suzdalenko Alexander
2014-12-01
Full Text Available The current measurement is becoming a challenging task in power converters operating at high switching frequencies, moreover traditional control system requires two control loops - first (slow regulates DC-link voltage, second (fast controls the shape of current, that all together results in complicated transfer function and long transition periods. The current sensorless control (CSC allows neglecting the mentioned problems. This research for the first time presents the solution of CSC implementation in single-phase three-level neutral point clamped inverter. Mathematical equations were defined for inductor current peaks and transistor conduction time during discontinuous and continuous conduction modes, as well as major problem of current fitting between different voltage levels (consequently with different current peak-to-peak values was solved, providing two solutions - pre-fitting and post-fitting trajectories. The verification of our theoretical assumptions and analytical equations was confirmed by the simulation analysis. Challenges of real experiments are discussed in the conclusion.
Tsourdi, Elena; Langdahl, Bente; Cohen-Solal, Martine; Aubry-Rozier, Bérengere; Eriksen, Erik Fink; Guañabens, Nuria; Obermayer-Pietsch, Barbara; Ralston, Stuart H; Eastell, Richard; Zillikens, M Carola
2017-08-05
The optimal duration of osteoporosis treatment is controversial. As opposed to bisphosphonates, denosumab does not incorporate into bone matrix and bone turnover is not suppressed after its cessation. Recent reports imply that denosumab discontinuation may lead to an increased risk of multiple vertebral fractures. The European Calcified Tissue Society (ECTS) formed a working group to perform a systematic review of existing literature on the effects of stopping denosumab and provide advice on management. Data from phase 2 and 3 clinical trials underscore a rapid decrease of bone mineral density (BMD) and a steep increase in bone turnover markers (BTMs) after discontinuation of denosumab. Clinical case series report multiple vertebral fractures after discontinuation of denosumab and a renewed analysis of FREEDOM and FREEDOM Extension Trial suggests, albeit does not prove, that the risk of multiple vertebral fractures may be increased when denosumab is stopped due to a rebound increase in bone resorption. There appears to be an increased risk of multiple vertebral fractures after discontinuation of denosumab although strong evidence for such an effect and for measures to prevent the occurring bone loss is lacking. Clinicians and patients should be aware of this potential risk. Based on available data, a re-evaluation should be performed after 5years of denosumab treatment. Patients considered at high fracture risk should either continue denosumab therapy for up to 10years or be switched to an alternative treatment. For patients at low risk, a decision to discontinue denosumab could be made after 5years, but bisphosphonate therapy should be considered to reduce or prevent the rebound increase in bone turnover. However, since the optimal bisphosphonate regimen post-denosumab is currently unknown continuation of denosumab can also be considered until results from ongoing trials become available. Based on current data, denosumab should not be stopped without considering
Takeuchi, Hiroyoshi; Kantor, Navot; Uchida, Hiroyuki; Suzuki, Takefumi; Remington, Gary
2017-01-01
Antipsychotic switching is routine in clinical practice, although it remains unclear which is the preferable switching method: immediate discontinuation of the current antipsychotic or a gradual tapering approach. The first strategy has been implicated in rebound/withdrawal symptoms and emergence/exacerbation of symptoms, whereas the gradual approach is thought to pose a risk of additive or synergistic side effects if employed in the context of a crossover approach. MEDLINE, Embase, and Cochrane Central Register of Controlled Trials were systematically searched. Randomized controlled trials examining immediate vs gradual antipsychotic discontinuation in antipsychotic switching in patients with schizophrenia and/or schizoaffective disorder were selected. Data on clinical outcomes, including study discontinuation, psychopathology, extrapyramidal symptoms, and treatment-emergent adverse events, were extracted. A total of 9 studies involving 1416 patients that met eligibility criteria were included in the meta-analysis. No significant differences in any clinical outcomes were found between the 2 approaches (all Ps > .05). Sensitivity analyses revealed that the findings remained unchanged in the studies where switching to aripiprazole was performed or where immediate initiation of the next antipsychotic was adopted, while some significant differences were observed in switching to olanzapine or ziprasidone. These findings indicate that either immediate or gradual discontinuation of the current antipsychotic medication represents a viable treatment option. Clinicians are advised to choose an antipsychotic switching strategy according to individual patient needs. This said, immediate discontinuation may be advantageous both for simplicity and because a stalled cross-titration process in antipsychotic switching could end up in antipsychotic polypharmacy. © The Author 2017. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All
Energy Technology Data Exchange (ETDEWEB)
Loescher, D.H. [Sandia National Labs., Albuquerque, NM (United States). Systems Surety Assessment Dept.; Noren, K. [Univ. of Idaho, Moscow, ID (United States). Dept. of Electrical Engineering
1996-09-01
The current that flows between the electrical test equipment and the nuclear explosive must be limited to safe levels during electrical tests conducted on nuclear explosives at the DOE Pantex facility. The safest way to limit the current is to use batteries that can provide only acceptably low current into a short circuit; unfortunately this is not always possible. When it is not possible, current limiters, along with other design features, are used to limit the current. Three types of current limiters, the fuse blower, the resistor limiter, and the MOSFET-pass-transistor limiters, are used extensively in Pantex test equipment. Detailed failure mode and effects analyses were conducted on these limiters. Two other types of limiters were also analyzed. It was found that there is no best type of limiter that should be used in all applications. The fuse blower has advantages when many circuits must be monitored, a low insertion voltage drop is important, and size and weight must be kept low. However, this limiter has many failure modes that can lead to the loss of over current protection. The resistor limiter is simple and inexpensive, but is normally usable only on circuits for which the nominal current is less than a few tens of milliamperes. The MOSFET limiter can be used on high current circuits, but it has a number of single point failure modes that can lead to a loss of protective action. Because bad component placement or poor wire routing can defeat any limiter, placement and routing must be designed carefully and documented thoroughly.
27 CFR 25.277 - Discontinuance of operations.
2010-04-01
... BUREAU, DEPARTMENT OF THE TREASURY LIQUORS BEER Pilot Brewing Plants § 25.277 Discontinuance of operations. When operations of a pilot brewing plant are to be discontinued, the operator shall notify the... operations have been completed and all beer at the premises has been disposed of and accounted for, the...
EVALUATING DISCONTINUITIES IN COMPLEX SYSTEMS: TOWARD QUANTITATIVE MEASURE OF RESILIENCE
The textural discontinuity hypothesis (TDH) is based on the observation that animal body mass distributions exhibit discontinuities that may reflect the texture of the landscape available for exploitation. This idea has been extended to other complex systems, hinting that the ide...
DISCONTINUOUS FINITE ELEMENT METHOD FOR CONVECTION-DIFFUSION EQUATIONS
Institute of Scientific and Technical Information of China (English)
Abdellatif Agouzal
2000-01-01
A discontinuous finite element method for convection-diffusion equations is proposed and analyzed. This scheme is designed to produce an approximate solution which is completely discontinuous. Optimal order of convergence is obtained for model problem. This is the same convergence rate known for the classical methods.
19 CFR 142.25 - Discontinuance of immediate delivery privileges.
2010-04-01
... SECURITY; DEPARTMENT OF THE TREASURY (CONTINUED) ENTRY PROCESS Special Permit for Immediate Delivery § 142.25 Discontinuance of immediate delivery privileges. (a) Authority of port director. The port director... 19 Customs Duties 2 2010-04-01 2010-04-01 false Discontinuance of immediate delivery privileges...
Contraceptive discontinuation and unintended pregnancy: an imperfect relationship.
Curtis, Siân; Evens, Emily; Sambisa, William
2011-06-01
Contraceptive discontinuation is a common event that may be associated with low motivation to avoid pregnancy. If this is the case, a substantial proportion of pregnancies that follow discontinuation will be reported as intended. Demographic and Health Survey data from six countries (Bangladesh, the Dominican Republic, Kazakhstan, Kenya, the Philippines and Zimbabwe) over the period 1999-2003 were used to explore the proportions of pregnancies women reported as intended or unintended following various contraceptive behaviors. Multivariate logistic regression analysis was used to examine the characteristics of women who reported births as intended when they followed contraceptive failure or discontinuation for reasons other than a desire for pregnancy. The proportion of births reported as intended following contraceptive failure ranged from 16% in Bangladesh to 54% in Kazakhstan, and the proportion reported as intended following discontinuation for reasons other than a desire for pregnancy ranged from 37% in Kenya to 51% in Kazakhstan. In at least half the countries, associations were found between selected women's characteristics and their reports that births following either contraceptive failure or discontinuation were intended: Factors that were positively associated were women's age and the time elapsed between contraceptive discontinuation and the index conception; factors that were negatively associated were increasing number of living children and reporting method failure as opposed to method discontinuation. These findings suggest that underlying variation in the motivation to avoid pregnancy is an important factor in contraceptive discontinuation.
27 CFR 20.68 - Notice of permanent discontinuance.
2010-04-01
... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Notice of permanent discontinuance. 20.68 Section 20.68 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE... Qualification of Dealers and Users Permanent Discontinuance of Business § 20.68 Notice of...
14 CFR Section 16 - Objective Classification-Discontinued Operations
2010-01-01
... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Objective Classification-Discontinued... AIR CARRIERS Profit and Loss Classification Section 16 Objective Classification—Discontinued... the disposal of investor controlled companies and nontransport ventures whether sold, abandoned,...
Automated extraction and analysis of rock discontinuity characteristics from 3D point clouds
Bianchetti, Matteo; Villa, Alberto; Agliardi, Federico; Crosta, Giovanni B.
2016-04-01
A reliable characterization of fractured rock masses requires an exhaustive geometrical description of discontinuities, including orientation, spacing, and size. These are required to describe discontinuum rock mass structure, perform Discrete Fracture Network and DEM modelling, or provide input for rock mass classification or equivalent continuum estimate of rock mass properties. Although several advanced methodologies have been developed in the last decades, a complete characterization of discontinuity geometry in practice is still challenging, due to scale-dependent variability of fracture patterns and difficult accessibility to large outcrops. Recent advances in remote survey techniques, such as terrestrial laser scanning and digital photogrammetry, allow a fast and accurate acquisition of dense 3D point clouds, which promoted the development of several semi-automatic approaches to extract discontinuity features. Nevertheless, these often need user supervision on algorithm parameters which can be difficult to assess. To overcome this problem, we developed an original Matlab tool, allowing fast, fully automatic extraction and analysis of discontinuity features with no requirements on point cloud accuracy, density and homogeneity. The tool consists of a set of algorithms which: (i) process raw 3D point clouds, (ii) automatically characterize discontinuity sets, (iii) identify individual discontinuity surfaces, and (iv) analyse their spacing and persistence. The tool operates in either a supervised or unsupervised mode, starting from an automatic preliminary exploration data analysis. The identification and geometrical characterization of discontinuity features is divided in steps. First, coplanar surfaces are identified in the whole point cloud using K-Nearest Neighbor and Principal Component Analysis algorithms optimized on point cloud accuracy and specified typical facet size. Then, discontinuity set orientation is calculated using Kernel Density Estimation and
Albelda, J.; Denia, F. D.; Torres, M. I.; Fuenmayor, F. J.
2007-06-01
To carry out the acoustic analysis of dissipative silencers with uniform cross-section, the application of the mode matching method at the geometrical discontinuities is an attractive option from a computational point of view. The consideration of this methodology assumes, in general, that the modes associated with the transversal geometry of each element with uniform cross-section are known for the excitation frequencies considered in the analysis. The calculation of the transversal modes is not, however, a simple task when the acoustic system involves perforated elements and absorbent materials. The current work presents a modal approach to calculate the transversal modes and the corresponding axial wavenumbers for dissipative mufflers of uniform (but arbitrary) cross-section. The proposed technique is based on the division of the transversal section into subdomains and the subsequent use of a substructuring procedure with two sets of modes to improve the convergence. The former set of modes fulfils the condition of zero pressure at the common boundary between transversal subdomains while the latter satisfies the condition of zero derivative in the direction normal to the boundary. The approach leads to a versatile methodology with a moderate computational effort that can be applied to mufflers commonly found in real applications. To validate the procedure presented in this work, comparisons are provided with finite element predictions and results available in the literature, showing a good agreement. In addition, the procedure is applied to an example of practical interest.
Directory of Open Access Journals (Sweden)
Gajria K
2014-08-01
Full Text Available Kavita Gajria,1 Mei Lu,2 Vanja Sikirica,1 Peter Greven,3,4 Yichen Zhong,2 Paige Qin,2 Jipan Xie2 1Global Health Economics, Outcomes Research and Epidemiology, Shire, Wayne, PA, USA; 2Health Economics and Outcomes Research, Analysis Group, Inc., Boston, MA, USA; 3Institute of Child and Adolescent Psychiatry, Psychotherapy and Social Pediatrics, Berlin, Germany; 4Department of Psychology and Mental Health, H:G University of Health and Sport, Technology and Arts, Berlin, Germany Abstract: Untreated attention-deficit/hyperactivity disorder (ADHD can lead to substantial adverse social, economic, and emotional outcomes for patients. The effectiveness of current pharmacologic treatments is often reduced, due to low treatment adherence and medication discontinuation. This current systematic literature review analyzes the current state of knowledge surrounding ADHD medication discontinuation, focusing on: 1 the extent of patient persistence; 2 adherence; and 3 the underlying reasons for patients’ treatment discontinuation and how discontinuation rates and reasons vary across patient subgroups. We selected 91 original studies (67 with persistence/discontinuation results, 26 with adherence results, and 41 with reasons for discontinuation, switching, or nonadherence and 36 expert opinion reviews on ADHD medication discontinuation, published from 1990 to 2013. Treatment persistence on stimulants, measured by treatment duration during the 12-month follow-up periods, averaged 136 days for children and adolescents and 230 days for adults. Owing to substantial study heterogeneity, comparisons across age or medication type subgroups were generally inconclusive; however, long-acting formulations and amphetamines were associated with longer treatment duration than short-acting formulations and methylphenidates. The medication possession ratio, used to measure adherence, was <0.7 for all age groups and medication classes during a 12-month period. Adverse