Variation Of Electrical Parameters Research Articles

Macrodipoles Unusual electric properties of biological macromolecules

The wide range of different effects induced by electric fields in biological macromolecules is clearly due to the unusual quality and quantity of their electric parameters. A general concept for a quantitative description of the polarizability of macromolecules remains to be established. In the case of DNA, experimental data indicate the existence of an effective polarization length N p ; at chain lengths N < N p the polarizability increases with N 2, whereas saturation is approached at N ≥ N p . The polarization length decreases with increasing ionic strength in close analogy to the Debye length, but is ∼10 times larger than the Debye length. The dynamics of DNA polarization at high field strengths has been observed in the ns time range and is consistent with biased field iduced ion dissociation. In the range of chain lengths from ∼400 to ∼850 base pairs DNA molecules exhibit permanent dipole moments, which are in a preferentially perpendicular direction to the end-to-end-vector, leading to a positive electric dichroism. These results are consistent with a “frozen” ensemble of bent DNA configurations and provide evidence for the existence of slow, non-elastic bending transitions. The electric parameters of proteins are usually dominated by a permanent anisotropy of the charge distribution, corresponding to permanent dipole moments of the order of several hundred Debye up to about 1500 Debye. Relatively small dipole moments of protein monomers add up to millions of Debye, when these proteins are in a vectorial organization in membrane patches, as found for bacteriorhodopsin and Na + K + -ATPase . In these cases the dipole vector may support vectorial ion transport. It is remarkable that the dipole moments of proteins usually show a relatively small dependence on the salt concentration; a rational for these observations is provided by a dipole potential at the plane of shear for rotational diffusion, which is defined in close analogy to the ζ-potential for translational diffusion. Symmetry breaking leading to huge electric dipole moments may be expected for mixed lipid vesicles: according to model calculations the phase separation of lipid components with and without net charges may lead to very high dipole moments; the expectation has been verified experimentally for vesicles containing DMPA and DMPC. The state of these systems should be extremely sensitive to electric fields. In summary, there is an unusual wide variation of electric parameters associated with biological macromolecules and with biomolecular assemblies, which is the basis for the complexity of different phenomena induced by electric fields in biological systems.

Structural and electrical characterisation of BICOCUVOX

Electrical conductivity behaviour and unit cell parameter variation have been investigated in the double substituted BIMEVOX system Bi2V0.9CoyCu0.1-yO5.35, 0<y<0.1 by a.c. impedance spectroscopy and X-ray powder diffraction. Variation of the unit cell volume indicates a microdomain structure for the material with Co rich and Cu rich regions. Both low and high temperature conductivities increase with increasing Co content. However, the overall conductivities appear to be lower than the two end members, BICOVOX and BICUVOX, which suggests that some type of defect trapping may be present in these double substituted systems.

Influence of network modifiers on conductivity and relaxation parameters in some series of fluoride glasses containing LiF

A new series of fluoride glasses of formulation ZrF 4(0.25)-ZnF 2(0.15)-YF 3(0.05)-AlF 3(0.10)-CdF 2 (0.17 − 2x 5 )-BaF 2(0.28 − 3x 5 )-LiF(x) and containing a wide LiF concentration range (0 ≤ x LiF ≤ 0.35) has been investigated by impedance spectroscopy: the variation of various electrical parameters has been determined as a function of composition. The results obtained with two other series of fluoride glasses covering the (0 ≤ x LiF ≤ 0.30) and (0.20 ≤ x LiF ≤ 0.60) concentration ranges are confirmed. A conductivity minimum associated with an activation energy maximum and a minimum of the decoupling index Rτ( T g ) takes place for x LiF ∼- 0.20. It is explained by the crossing with increasing x from a conductivity due preferentially to F − ions to a conductivity due preferentially to Li + ions. Within each series, the composition relative to conductivity minimum offers a value r ⋍ 1 of the ( x LiF x BaF 2 ) ratio. For higher x LiF rates, the β conductivity relaxation parameter involves also a minimum. Comparison of various series studied indicates that the composition relative to β minimum offers a value r ⋍ 2 of the ( x LiF x BaF 2 ) ratio. The structural origin of the β minimum is confirmed.

Parametric variations in dynamic models of induction machine clusters

This paper presents a probabilistic approach to the characterization of dynamical models of induction machine clusters. The authors' method derives bounds on eigenvalue variations for linearized models expressed in terms of stochastic norms. In their examples of the modeling of power system loads, this characterization tends to be less conservative than alternative deterministic approaches. They consider examples of induction machines with different ratings (classes), and allow for wide variations of electrical and mechanical parameters. They describe a stochastic norm approach to: (1) efficiently describe the dynamical model variations for a cluster of similar machines without having to perform repeated eigenvalue calculations, e.g. in a wind farm application; and (2) suggest the order of the reduced model in power system load modeling where the tightness of the bounds of eigenvalue variations is used for guidance in decisions regarding the number of different classes that would efficiently represent a given composite load.

Hippocampal electrical activity and behavior in the rabbit.

Different approaches to the study of the relationship between hippocampal electrical activity and behavior have shown that hippocampal EEG varies according to different behavioral aspects. In particular, a rhythmic slow activity (RSA, Theta rhythm) can be recorded during voluntary movements and to a lesser degree during immobility. In laboratory experiments, we tried to evaluate the influence on the hippocampal EEG of external stimuli evoking emotional or cognitive responses. Similar electrical responses were observed during animal hypnosis and in the presence of threatening stimuli, while some electrical parameters, such as frequency and rhythmicity, varied according to the nature of the stimulus. In order to have greater and clearer information, we adopted a neuro-ethological approach ch. which allowed us to classify behavior into several categories and to record the hippocampal EEG during natural behavior. The influence exerted on hippocampal electrical activity by novel stimuli and the electrical profiles recorded during exploratory behavior or alert or quiet immobility allowed us to classify the hippocampal EEG on the basis of frequency and rhythmicity. Moreover, the study of social behavior showed that the variations of the electrical parameters of the hippocampal activity depended on the characteristics of the stimulus and that typical electrical profiles could be observed in immobile or motor activities caused by specific stimuli. Socially dominant and subordinate rabbits could also be distinguished on the basis of hippocampal electrical parameters.

High Performance Speed Control Based on Instantaneous Speed Observer Considering the Characteristics of DC Chopper in Low Speed Range

This paper proposes a new high performance speed control method for wide speed range, which is based on instantaneous speed observer considering the characteristics of DC chopper. In order to regulate a motor speed for wide speed reference including a very low speed range, this paper designs the instantaneous speed observer which uses the information of an armature current and an armature voltage. This observer has no effect of inertia variation and disturbance torque completely, but it has the effect of electrical parameter variation. Hence, this paper proposes a new identification algorithm to cancel out the estimation error caused by both the resistance variation and the voltage drop. The proposed observer can always estimate an instantaneous value of motor speed. The proposed total system becomes a new robust speed servo system for a wide speed range.

Relationship between profile of stressgenerated interface traps and degradation of submicron LDD mosfet's

By relating the complete spatial interface trap profile to the variation of electrical parameters in n-channel LDD and FOND MOSFET's, we clarify the respective role of defects above the channel and the LDD region. We show that the saturation of the series resistance increase is due to the leveling off of the rate of interface trap generation and not to the self-limiting impact of such defects on the series resistance. The importance of the choice of the parameter used to estimate the lifetime is demonstrated.

Offset-trimming bit-line sensing scheme for gigabit-scale DRAM's

A new offset-trimming bit-line sensing scheme is described which is suitable for gigabit-scale DRAM's. This sensing scheme can suppress the sensitivity degradation caused by the large electrical parameter variation of deep submicron transistors. The effective offset voltage dependence on trimming time is analyzed and verified with simulation results. As compared with a conventional direct sensing scheme, the proposed scheme shows remarkable improvement on the sensitivity. A test device was fabricated with a 0.25 /spl mu/m CMOS technology and its measurement results indicate the successful operation of offset-trimming.

Annealing effect on conductivity anisotropy in indium selenide single crystals

Electrical conductivity along and across the layers, its anisotropy, and the Hall effect for undoped and annealed Te-doped samples of InSe are investigated in the temperature range 80 to 400 K. Variations of electrical parameters of annealed samples are determined during the relaxation process. It is established that peculiarities of the annealing effect as well as the relaxation process in annealed samples are induced by the presence of interlayer impurity precipitates of In atoms adsorbed by stacking faults. High values of the anisotropy ratio in n-InSe and its activated character below 250 K are caused by these impurity aggregates.

F − ion conductivity and diffusion properties in ZrF 4-based fluoride glasses with various NaF concentrations (0 ⩽ xNaF ⩽ 0.45)

Selecting two series of ZrF 4-based fluoride glasses containing at the same time the BaF 2 and NaF network modifiers and a third series with NaF only, an investigation of electrical and diffusion properties has been undertaken as a function of x NaF in a wide concentration domain (0 ⩽ x NaF ⩽ 0.45). The ac conductivity data have been analysed by the complex modulus formalism and a hopping mechanism for transport in these materials is suggested. The 23Na and 19F NMR investigations have shown that Na + ions do not participate as charge carriers in the conduction mechanisms and the diffusion properties are due only to motions of mobile F − ions. Mobility and number of F − ions mobile in the NMR time scale increase when x BaF 2 increases, result in agreement with the composition dependence of electrical properties at long range. Experimental points representative of log σ 473 K and ΔE σ as a function of x NaF for the glasses studied are located on both sides of “master” curves involving a conductivity minimum and an activation energy maximum for x NaF ∼- 0.30. Variation of the decoupling index, R τ ( T g), with x NaF is in agreement with that of σ 473 K in the whole of the studied composition. On the contrary, the variation of the Kohlrausch parameter, β, is more difficult to analyse and may be explained by the coupling model only for x NaF ≲ 0.15. The variation of various electrical parameters is discussed as a function of glass composition.

Electrical behaviour of polysilicon solar cells modified by the electrochemical coating of heteropolyanions

A new method for treating photovoltaic solar cell front surfaces is presented in this article. The cell front surfaces are treated by electrodeposition of heteropolyanions. Improvements in the I–V characteristics of the solar cells have been observed. We also noticed that this treatment causes a 12.61% increase in the short-circuit current and an 11% increase in the efficiency. The variation in the solar cell's electrical parameters with treatment time and operating conditions are seen by the effect on cell performance.

Influence of the forming electrolyte on the electrical properties of anodic zirconium oxide films: Part II. Ac impedance investigation

The potentiodynamic oxidation of Zr at ν = 0.05 V s −1 was investigated in the potential range 0–90 V in the following electrolytes: H 2SO 4, HNO 3, H 3PO 4 and NaOH. After film growth, the oxides were characterized by ac impedance measurements in the frequency range 0.1 Hz ≤ f ≤ 10 kHz. The impedance responses of the films formed in H 2SO 4 and NaOH were modelled with a transfer function corresponding to a single-layer model. The impedance spectra of the oxides formed in H 3PO 4 and HNO 3 showed two time constants which were adequately simulated by a transfer function corresponding to a two-layer oxide structure. The nature of the outer layer of the films formed in H 3PO 4 was attributed to phosphate incorporation from the electrolyte, which was confirmed by X-ray photoelectron spectroscopy measurements. The variation of the oxide electrical parameters (resistance, capacitance etc.) with final formation potential is reported and the reasons leading to the complex film structure are discussed.

A manufacturing sensitivity analysis of 0.35 μm LDD MOSFET's

Fundamental to successful manufacturing of integrated circuits is the achievement of sufficient control in all process steps to realize, with very high yield, fully functional circuits whose performance and reliability conform to pre-determined standards. Towards this end, it is increasingly necessary to relate in a quantitative manner the sensitivity of the electrical performance of the final devices and circuits to variations in structural parameters and doping profiles, which in turn can be related to process and tool performance variations. In this paper, we describe the results of an analysis performed to quantify the sensitivity of the electrical parameters of a 0.35 /spl mu/m LDD MOSFET to variations in the doping and structural parameters of the device that are anticipated in manufacturing. A central-composite design was used to develop second-order models for six key device electrical parameters. The resulting models are manifested as second-order equations relating the device electrical parameter variations to random variations in seven key device structure and doping parameters. This set of equations thus allows one to understand quantitatively the source and nature of the device electrical parameter variations. A simple Monte Carlo approach is applied to predict the statistical distributions of the key device electrical parameters which result from the random manufacturing variations in the structure and doping parameters by using the quantitative relationships developed in this paper. >

Degradation of silicon AC-coupled microstrip detectors induced by radiation

Results are presented showing the radiation response of FOXFET (field-oxide field effect transistor) biased AC-coupled microstrip detectors and related test patterns to be used in the CDF microvertex detector. The radiation tolerance of detectors to gamma and proton irradiation has been tested, and the radiation induced variations of the DC electrical parameters have been analyzed. The long-term post-irradiation behavior of detector characteristics has been studied, and the relevant room-temperature annealing phenomena have been considered. The main radiation damage effects after gamma or proton irradiation of FOXFET biased microstrip detectors consist of an increase of the total leakage current, while both the detector dynamic resistance and FOXFET switching voltage decrease. No radiation-induced variation of the strip self bias Vso is measured up to 1 Mrad. The above variations are due to the generation of Si/SiO/sub 2/ interface traps and positive charge accumulation in the oxide film, as confirmed by C-V measurements on MOS capacitors. >

Factors influencing long-term in vivo reproducibility of QCT overtebral densitometry).

We investigated the long-term in vivo reproducibility of quantitative CT (QCT) examinations that were conducted in conformity with a standard and well established methodology. The long-term reproducibility in vivo of QCT vertebral densitometry was studied in 12 normal postmenopausal women (mean age 51 years), who underwent four to five examinations over the same 2 year period. One group of six patients demonstrated good reproducibility with a coefficient of variation (CV) of bone mineral density (BMD) of < 2.4% and were considered "good cases." The other group of six patients showed poor reproducibility with a CV of BMD of > 3.2% and were considered "problem cases." A statistical study of the technical parameters of the QCT examination was performed to determine and correct for the factors that are correlated with reproducibility errors. Analyzing uncalibrated variations in Hounsfield numbers, we found that the surrounding soft tissues such as muscle, aorta, liver, and fat were correlated in both the good and the problem cases. However, only in the good cases did we find that the Hounsfield numbers of the vertebral bodies correlated strongly with the soft tissues and with parameters characteristic of the calibration regression line. Essentially, the calibration procedure appeared to fail in some examinations of the problem cases, causing poor long-term reproducibility. This calibration failure may be related to positioning of the subject in the gantry and to variations in electrical parameters of the X-ray tube. A CV > 1% between the four slopes of calibration for the individual vertebrae measured at the same visit may indicate calibration problems and may suggest the need for repeat scanning.

Effect of rapid thermally nitrided titanium films contacting silicided and nonsilicided junctions

The effect of rapid thermally nitrided titanium films contacting silicided (titanium disilicided) and nonsilicided junctions has been studied in the temperature range of 800 to 900°C. The rapid thermal nitridation of titanium films used as diffusion barriers between aluminum and silicon, has a major impact on shallow junction complementary metal oxide semiconductor technologies. During the process of rapid thermal nitridation, the dopants in the junctions undergo a redistribution and affect the electrical properties of shallow junction structures. This work focuses on using novel contact resistance structures to measure the variation in electrical parameters for rapid thermally nitrided titanium films annealed at different temperatures. The self-aligned silicide (salicide) junctions in this study were formed using rapid thermally annealed titanium films. Electrical contact resistance testers were used to measure the interface contact resistance between the salicide and silicon, as well as between the metal and the salicide. The results show that the interface contact resistance to the p− diffused salicided junctions increases with rapid thermal nitridation of the additional titanium film, whereas the interface contact resistance to the n− diffused salicided junction shows a decrease. Further, as a function of the rapid thermal annealing temperature (for fixed titanium thickness), the nonsalicided diffusions show an increase in the interface contact resistance. The boron profiles at the TiSi2/Si interface obtained using secondary ion mass spectroscopy show an excellent qualitative agreement with the electrical results for each of the conditions discussed. The films were also characterized using Rutherford back-scattering spectrometry and transmission electron microscopy and the results show good agreement with the measured variation in electrical parameters. These results also show that as the anneal temperature is increased, the TiN thickness increases, further the change in the silicide/silicon interface position with the nitridation of the additional titanium layer was verified.

Digital voltage vector control with adaptive parameter tuning

This paper describes a completely digital control system for standard induction motors. A new inverter voltage vector control system for high frequency switching has been designed, and a predictive frequency-voltage control system that eliminates the need of tacho feedback has been developed. In addition, an adaptive parameter tuning method has been developed. This method takes the large variation in electrical parameters of standard induction motors of different manufactures into account. For control purposes, switch protection and switch loss minimizing, custom designed application specific integrated circuits have been used extensively. Steady-state and dynamic performances of the drive are documented and compared to simulations.

Dependence of optical receiver sensitivity, in a 147-Mbit/s heterodyne DPSK system, as a function of optical and electrical parameter variations

Measurements of the changes in optical receiver sensitivity are described. They are caused by (a) the effect of bandpass and low-pass filtering, (b) the dependence on integer and noninteger values of the intermediate-frequency-to-bit-rate ratio, (c) the influence of the local oscillator power, and (d) the impact of deviation from ideal pi phase-shift modulation. The studies were conducted at lambda =1.523 mu m and at a bit rate of 147.75 Mb/s, using external-cavity lasers with negligible phase noise. The results demonstrate the conditions for optimum DPSK system performance in the absence of laser phase noise. The receiver degradation observed for deviations from optimal electrical and optical conditions have been measured and found to be in good agreement with earlier theoretical calculations of microwave phase modulated schemes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Decaying arc response to the voltage peak

A wall-stabilised argon arc (35 A) submitted to recurring decay and reignition is disturbed during its decay phase by a high-voltage peak which includes some electrical parameter variations. The spectral observation of this event is presented. This study shows that the arc conductance variation for a short voltage pulse arises from electron heating.

Characterization of bone materials as ultrasonic transducers

Physical, dielectric, piezoelectric and electromechanical parameters have been reported for bone and its two major constituents i.e. collagen and apatite, for their characterization as ultrasonic transducer materials. Collagen and apatite have been extracted from full bone using well known methods. These materials have been used to prepare simple disc-shaped test pieces (dimensions: diameter 10 mm and thickness 1.0 ± 0.01 mm). The variation of various electrical parameters with frequency in the region (1–108 MHz) is examined for these materials. These include impedance, phase angle, relative voltage output, quality factor ‘Q’, dielectric constant and resistivity. The data so obtained are compared with those for ceramic and quartz transducers. The observations on impedance, phase and relative voltage output for bone materials indicate that the first resonance peak falls around 56 MHz followed by second and third harmonics around 112 MHz and 168 MHz respectively. A low ‘Q’ value suggests a fairly wide band transducer, while other parameters compare favourably with ceramic and quartz materials. Bone material has also been used to obtain a transducer in the standard configuration and velocity dispersion in the frequency range 1–108 MHz is examined.