Current Response Time Research Articles

Using mixed gases for massive gas injection disruption mitigation on Alcator C-Mod

Mixed gases are used for massive gas injection disruption mitigation on Alcator C-Mod in order to optimize radiation efficiency, halo current reduction and response time. Gas mixtures of helium and argon (argon fraction 0–50%) are investigated in detail, as well as mixtures of deuterium, argon, krypton and helium. Experiments show that injecting He/Ar mixtures leads to faster thermal and current quenches than with pure helium or argon injection, thus improving the time response of the disruption mitigation system and reducing the halo current. Small fractions of argon (∼5–10%) in helium also lead to optimized radiation fractions with large electron density increases in the core plasma. These results are consistent with the expectation that small fractions of argon will be entrained with the faster helium in the early phases of gas flow. The gas mixing allows one to simultaneously exploit the fast particle delivery rate of light helium gas and the large radiation capability of argon.

Dynamic performance estimation of stator voltage regulator in rotary exciter system with DC exciter

In this paper, procedure for AVR parameter estimation is proposed, based on step responses when synchronous generator in idle run. The exciter system includes AVR, thyristor rectifier and DC exciter. AVR is realized in the form of cascade control structure with two control loops. PID controller in the outer loop represents the primary controller. P controller in the inner loop represents secondary controller which enables the faster field current response time. The aim of procedure is to determine equivalent gain of PID controller and thyristor rectifier. The measurements used in the parameter estimation procedure are taken from fossil power plant 'Kolubara A', aggregate A5.

Study on I–V characteristics of lead free NTC thick film thermistor for self heating application

The resistivity of several materials varies predictably with temperature; this makes them suitable for the use as temperature sensors. If these material gets heated due to the electric current passing through it and if it preserves a uniform temperature distribution during heating, then its total resistance would accurately reflect its temperature, allowing it to simultaneously act as both a temperature sensor and a self heater. This paper describes the results of indigenously formulated lead free thick film NTC thermistor paste composition with sheet resistance of 1 kΩ/□ used for heater application. The current–voltage, temperature–current characteristics, dissipation constant, response and recovery time of the heater are reported. The maximum current handling capacity of the prepared thick film thermistor was observed at 300 m A and the temperature achieved to 340 °C. Therefore, the heater was tested at a constant current of 300 m A for 24 h, which did not show any extreme change in behaviour and the temperature of the thermistor/heater remained constant to 340 ± 5 °C.

The fabrication and characterization of granular aluminium/palladium bilayer microbolometers

Superconducting granular aluminium/palladium bilayer microbolometers with subnanosecond response can be easily fabricated using an all lift-off process with image-reversal lithography. The palladium capping layer allows for convenient and reproducible Ohmic contacts to be made to the device. We report their fabrication, resistance–current calibration, responsivity and response time. Finally, a deconvolution algorithm is used to improve the time resolution to approximately 1 ns while obtaining the incident photon and phonon fluxes in both direct photoexcitation and phonon heat pulse experiments.

Enhancing chemiresistor-type NO gas-sensing properties using ethanol-treated lead phthalocyanine thin films

The gas-sensing properties of ethanol-treated lead phthalocyanine (PbPc) thin films, to be used in a chemiresistor-type nitric oxide (NO) gas sensor, are presented. The gas-sensing properties, including current transient, sensitivity, and response time, were studied. It was found in this study that the PbPc thin films post-treated with an ethanol (EtOH) vapor responded faster to NO gas both in adsorption and desorption processes, comparing to those PbPc thin films without any post-treatment. The sensitivity was also enhanced with the post-treatment. A nonlinear diffusion–adsorption model, proposed in the literature for gas-sensing with a semiconductor thin film, has been used to fit our experimental data. The results obtained from the fitting revealed that the EtOH-treated PbPc thin films possess a larger effective diffusion coefficient and a faster response time. For 100-nm PbPc thin films, the power indexes (sensitivity) for both untreated and treated films are 0.38 and 0.65, respectively. Moreover, the model also gives other physical parameters for both untreated and EtOH-treated PbPc films.

Schedulability analysis of periodic fixed priority systems

Feasibility analysis of fixed priority systems has been widely studied in the real-time literature and several acceptance tests have been proposed to guarantee a set of periodic tasks. They can be divided in two main classes: polynomial time tests and exact tests. Polynomial time tests can efficiently be used for online guarantee of real-time applications, where tasks are activated at runtime. These tests introduce a negligible overhead, when executed upon a new task arrival, however provide only a sufficient schedulability condition, which may cause a poor processor utilization. On the other hand, exact tests, which are based on response time analysis, provide a necessary and sufficient schedulability condition, but are too complex to be executed on line for large task sets. As a consequence, for large task sets, they are often executed off line. This paper proposes a novel approach for analyzing the schedulability of periodic task sets on a single processor under an arbitrary fixed priority assignment: Using this approach, we derive a new schedulability test which can be tuned through a parameter to balance complexity versus acceptance ratio, so that it can be used on line to better exploit the processor, based on the available computational power. Extensive simulations show that our test, when used in its exact form, is significantly faster than the current response time analysis methods. Moreover the proposed approach, for its elegance and compactness, offers an explanation of some known phenomena of fixed priority scheduling and could be helpful for further work on schedulability analysis.

Experimental analysis of magnetorheological dampers for structural control

The possibility of reducing structural response under strong external excitationssuch as earthquakes and wind storms via control systems is attracting the interestof a large number of researchers. In the field of civil structures, control systemsbased on semi-active devices seem to be close to feasible implementation.Semi-active devices are typically passive elements capable of self-adjusting theirown mechanical properties according to the instantaneous response of thehosting structure and, therefore, they can be considered as smart devices.Even though dampers based on magnetorheological fluids are consideredvery effective in practical implementations, the literature examining theirproperties from the structural control point of view is still quite limited.This paper aims to show the potential of such devices and to describetheir properties from this special perspective. These properties includemanufacturing issues, powering, range of variability of the mechanicalparameters, their dependence on the feed current and overall response time.

Capillary-electrode alignment by an optical-fiber connector for amperometric detection in capillary electrophoresis.

We describe here an electrochemical cell ideal for routine analysis of CE-EC experiments (capillary electrophoresis coupled with electrochemical detection). The cell was modified from a fiber-optic connector, named MT, which allowed frequent change and fast alignment between a pair of 4-strand fiber ribbons. The relative standard deviations of the current response and migration time for 100 microM dopamine were, respectively, 3.7 and 0.5% in five repetitive routines of disconnecting, polishing, and assembling the CE cell. The time required for alignment of the separation capillary and the working electrode was < 10 s, once all components were assembled in an MT fiber-optic plug. These features enabled CE-EC users to polish the working electrode and reassemble the EC cell as in HPLC-EC. However, to accommodate the channel dimensions of the commercially available MT, a special order capillary with outer diameter of 125 microm is necessary at this stage.

Chemiresistor-type NO gas sensor based on nickel phthalocyanine thin films

The sensing characteristics of nickel phthalocyanine (NiPc) thin films for use in a chemiresistor-type nitric oxide gas sensor are discussed. The gas-sensing properties, including current transient, sensitivity, response time, and aging, are studied. A kinetic model proposed in the literature for sensing NO 2 with lead phthalocyanine (PbPc) thin films, in which adsorption involves displacement of surface adsorbed O 2 from a range of heterogeneous sites, can be used to explain our experimental results. It is inferred that exposure to NO concentrations lower than 50 ppm only involves the population of weak adsorption sites, while exposure to NO concentrations higher than 50 ppm may involve the population of stronger adsorption sites. Repeated step changes in NO concentrations of 50 ppm could result in a significant change in response currents within the first five cycles, presumably due to the presence of an irreversible adsorption. Further analysis of current responses reveals that the lower the concentration of NO, the larger the sensitivity. For a lower concentration range, between 5 and 50 ppm NO, the sensitivity lies between 0.41 and 0.42, while for a higher concentration range, between 50 and 500 ppm, the sensitivity decreases to about 0.17 to 0.19.

Synthesis and physical properties of laterally fluoro substituted ferroelectric liquid crystals with a fluoro substituted chiral terminal chain

A new series of ferroelectric liquid crystals (FLCs) has been designed for active matrix displays based upon the chiral smectic C phase. The FLCs have been derived from optically active fluorinated alkanols and a laterally fluoro substituted biphenylyl-1,3-dioxan core. Their physical properties such as spontaneous polarization, current response time, and tilt angle have been determined. The FLC derived from 2-fluoro-octanol showed a very short current response time of 10μs at T Sm*-N* - T= 10°C, while another FLC with the same core derived from 5-fluoro-octanol gave a value of 150μs.

Simplified methods for determining the ionic resistance in a porous electrode using linear voltammetry

Two simplified methods are proposed for determining the internal ionic resistance of a porous electrode using linear voltammetry in the double layer region. With the 70% current response time t 0.7 on linear voltammogram and the independently measured uncompensated solution resistance R e, the internal ionic resistance of a porous electrode can be calculated using the equation R p=2.483 t 0.7/ C total−2.989 R e, where C total is the total capacitance of the porous electrode and can be deduced from the plateau current on the voltammogram. When R p is not much smaller than R e, it is also possible to estimate the ionic resistance according to the curve shape of the linear voltammogram without knowing R e.

Control System of Permanent Magnet Synchronous Motor for Railway Vehicle Traction.

The application of a permanent magnet synchronous motor (PMSM) has been studied for railway vehicle traction in order to reduce the weight and size of direct drive traction motors. As a part of this study, it is required to establish a current control system of PMSM suitable for railway vehicle traction. This article discusses the current control system mentioned above and suggests a method which is available under the condition of railway vehicle traction. Next, an investigation is conducted on how to decide the current response time constant. The article will also show that the suggested traction control system is sufficient in practical use through an analysis of operating status under the condition of actual railway vehicle traction.

ER Suspensions of Sulfonated Poly(Styrene-CO-Divinylbenzene) Particles

Two ER suspensions (ERF1 and ERF2) containing highly sulfonated poly(styrene-co-divinylbenzene) particles (ERP) were newly prepared. The ERP concentration was 20 wt% in ERF1 and 40 wt% in ERF2. The ER properties of the suspensions were investigated in view of applications to practical devices. The investigated properties were zero-field viscosity, dispersion stability, induced shear stress, current density, response time, shear rate and temperature dependence of the induced shear stress and current density, response time, shear rate and temperature dependence of the induced shear stress and the current density. electrical durability. In the results, it was found that ERF1 and ERF2 had a very high potential for practical applicatons. The remarkable characteristic of ERF1 was the very low zero-field viscosity of 35 mPa·s at 25°C. The remarkable characteristic of ERF2 was very large induced shear stress and under applying DC 4 kV/mm at 25°C, the induced shear stress was 5.1 kPa. As an application example, the ERFs can be efficiently used for an ER Cutting Machine incorporating variable speed rodless cylinders. The machine has worked smoothly for one and a half years, although the characteristic of control slightly changed.

The Physical Properties of A Series of Antiferroelectric Hetrocyclic Esters

A series of highly chiral hetrocyclic esters have been studied. The effect that the choice of hetroatom has on the linearity of the molecules and hence the mesomophism of the materials has been investigated. Measurements of the spontaneous polarisation, tilt angle, current response time and rotational viscosities of the materials are reported. At 30°C below the transition from the SmA phase all members of the series show a Ps of ∼100nCcm−2 and a high tilt angle of about 30°. These physical measurements confirm the presence of a higher order antiferroelectric phase in the selenophene derivative in this series.

Immobilization of uricase to gas diffusion carbon felt by electropolymerization of aniline and its application as an enzyme reactor for uric acid sensor

Electropolymerizations of aniline and pyrrole solutions containing uricase at a neutral pH was performed to immobilize the enzyme on the surface of the gas diffusion carbon felt, and a selective uric acid sensor was fabricated by combining immobilized enzyme carbon felt and an oxygen electrode with oxygen gas permeable membrane. This carbon felt has a desirable feature for uricase sensing because an extremely efficient supply of oxygen for the enzymatic reaction can be realized due to its porosity permitting a transfer of oxygen. The current response time required from when sample is added until when current reaches the steady-state value is <5 min. The calibration graph of uric acid showed a linear line in a concentration range from 1×10−5 to 4×10−4 M with a detection limit of 4×10−6 M.

Forward current transients in amorphous silicon p-i-n structures

The transient forward current in several specimens of a-Si:H p-i-n structures was studied as a function of applied voltage, temperature, and illumination as well as the degradation of the samples. The results show that the delay time of the current onset from its initial decay relates to the initial electron space-charge-limited current with a power law, t d α ( I SCLC) − γ , where γ is a constant which is insensitive to the measurement conditions such as temperature and illumination but depends on the properties of devices such as the density of states in the intrinsic layer. Therefore, the value of γ is a measure of the quality of devices. The current-response time product, I f t r, is largely independent of the applied voltage for specific samples.

New low molar mass organosiloxanes with unusual ferroelectric properties

Abstract A new low molar mass chiral organosiloxane mesogen and its racemic analogue have been synthesized and their mesomorphic and ferroelectric properties investigated. The chiral derivative, denoted A∗B, exhibits one tilted enantiotropic ferroelectric smectic C mesophase over a broad temperature range, with very high tilt angles and moderate spontaneous polarization (36° and 19 nC cm−2 at 20°C). The achiral siloxane derivative, denoted A∗B, exhibits one broad enantiotropic smectic C phase. Preliminary electro-optic measurements indicate that the spontaneous polarization is weakly dependent on temperature between 10°C and 50°C, the latter being the S∗c to isotropic phase transition. The tilt angle and layer spacing are temperature independent, and current response times of less than 200 μs were measured at 25°C for fields of 10 V μ−1. These results are discussed in comparison with those for side chain polymer liquid crystal structures and other low molar mass ferroelectric materials.

A Public Safety Merger in Grosse Pointe Park, Michigan—A Short and Sweet Study

The city of Grosse Pointe Park, Michigan planned to totally merge its police department and fire department, which also provided emergency medical services. Almost all personnel would be trained as both policemen and firefighters, and many as emergency medical technicians. The firefighters opposed the merger and forced a referendum. In 17 days, we documented the excellent current response times and found that a merger could reduce operating costs by as much as $100,000 per year, further reduce response times, increase patrol coverage, and add an additional detective.

Two-dimensional effects in intrinsic photoconductive infrared detectors

Two-dimensional effects on the current responsivity and response time of intrinsic quantum photoconductive infrared detectors are presented in detail. Deviations from first-order theory are shown to be pronounced for the case of devices of small optically sensitive area with planar electrodes. Expressions are derived that lend themselves to numerical calculations. Specific results are given for Hg 1− x Cd x Te detectors of various geometries and operating conditions. A novel structure for a photoconductive detector array with asymmetric contacts is proposed and analysed.

A controlled VLF Phase Reversal Experiment in the magnetosphere

Abstract : During the 1973 operations of the transportable very-low-frequency (TVLF) transmitter near Anchorage, Alaska (L approx. 4), an experiment was performed to determine the effect of controlled phase changes of the transmitted wave on the magnetospherically propagated signal received in the conjugate region. At periodic intervals, the phase of the driving voltage was changed (essentially instantaneously) by 180 deg. The amplitude of the 6.6 kHz signal detected in the conjugate region went to zero and recovered with a characteristic time constant of 33 msec. This is ten times longer than the antenna current response time and is in fact comparable with characteristic electron interaction times with whistler-mode waves. Between the times at which the phase reversals occurred, the received signal was amplitude modulated. The period of the modulation was about 26 msec. An upper sideband was present in the spectrum while these pulsations were occurring. These characteristic times are in general agreement with theoretical predictions of bandwidths, growth rates, and particle trapping frequencies for whistler instabilities in the magnetosphere. Data obtained from the controlled transmissions and from lightning generated whistlers propagating in the same duct were combined to determine the plasma and wave parameters at the geomagnetic equator. Of particular interest is the level at which the magnetic field of the wave saturated. During the time period for which the data were analyzed, this was found to be 3.5 pT. (Author)