Circle Diagram Research Articles

Measurement of Viscoelastic Properties of Polymer Solutions by Torsional Crystals

The network analyzer was used for measurement of the viscoelastic properties of dilute polymer solutions. It is a sensitive instrument to measure resonance resistance and resonant frequency of crystals by the admittance circle diagrams shown on the digital oscilloscope. Measurements can be conducted more correctly and rapidly compared to the previous measuring system. Its validity was verified by measuring the complex shear modulus of dilute polymer solutions and comparing the results with the Rouse theory. The complex shear modulus was determined by measuring changes in the properties of a torsionally vibrating crystal. Frequency dependence of complex shear modulus is investigated in the frequency range from 3 to 252 kHz and temperature range from −60 to 23°C. The samples are several kinds of dilute solutions of polystyrene in toluene. The use of polystyrene is limited in narrow molecular weight fractions ranging in number-average molecular weight from 2.1×103 to 1.60×105. The results agreed with the theory by Rouse.

Application of GPT to tan delta measuring apparatus for distribution cable in hot line

A hot line tan delta measuring apparatus which uses the secondary voltage of GPTs (grounding potential transformers) existing at substations and other facilities has been developed. An error vector circle diagram method which allows one to determine the value of tan delta to an accuracy of 0.1%, notwithstanding the phase difference existing between the primary and secondary voltages of a GPT, is described. The method was used in field experiments with favorable results. The method is especially superior in terms of safety and operability because no contact with high-voltage portions is required.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Propagation in a stratified medium with an extension of the circle diagram

In previously described work, the circle diagram technique was extended to propagation whose characteristic impedance was approximated by a step-wise variation or was imaginary. This paper describes an extension in which the point impedance is found by solving a generalized Riccati equation. A normalized impedance is used so that one diagram can be applied to a class of variations. The solution is given by two orthogonal families of curves: curves of constant phase and curves of constant standing-wave ratio. The field can be obtained by a simple integration of an associated differential equation. The magnitude of the field can be obtained from a simple algebraic formula for the intensity. A simple solution is obtained for the case of a layer in which the variation of the characteristic impedance is linear; by a simple transformation, the impedance diagram is a bipolar plot. A brief connection between the graphical and analytic methods is made.

Evidence for a weak and overpressured décollement beneath sediment‐dominated accretionary prisms

We present structural data from several underthrust sequences in southwest Alaska that suggest that the deformation regime beneath accretionary prisms is characterized by a subvertical σ1 and regionally extensive layer‐parallel shearing. These results contrast markedly with the results obtained from the more shallow parts of accretionary prisms and fold and thrust belts where σ1 plunges gently seaward or toward the deformation front. On the basis of Mohr circle diagrams, we propose that these different stress directions are consistent only with a model in which the two regimes are separated by a very weak décollement and calculate coefficient of friction values that range from 0.25 to 0.08. These values are significantly lower than coefficient of friction values calculated for the basal décollement in the Taiwan fold and thrust belt (e.g., ±0.2 (Barr and Dahlen, 1989a)) and they are also lower than laboratory friction measurements for most rocks (e.g., 0.6–0.8 (Byerlee, 1978)). Consequently, these low values suggest the presence of rocks with unusual material properties (e.g., montmorillonite (Logan and Rauenzahn, 1987)) or anomalous fluid pressures along the décollement. On the basis of the occurrence of shale diapirs, the distribution of early veins, and the absence of montmorillonite in the underthrust sequences, we propose that there was an anomalously high fluid pressure along the décollement fault instead of there being such a low coefficient of friction. These results emphasize the importance of dewatering and fluid flow in controlling the position of the décollement, which in turn determines how the accretionary prism grows. In essence, it is the development of a weak, overpressured décollement within a thick sediment pile that allows plate convergence to be partitioned into offscraping and underthrusting regimes.

Circle diagrams applied to the design of thin film optical tunnel filters

Diagrams of complex reflectance or circle diagrams are used to design optical coatings at normal incidence. The technique can be extended to oblique incidence, including the design of coatings which take advantage of total internal reflectance. Use of these diagrams is helpful in visualizing and compensating for polarization effects in such coatings.

Interpretational errors in syllogistic reasoning

The purpose of this research was to investigate whether subjects interpret quantifiers in the way predicted by theories of syllogistic reasoning. In Experiment 1, subjects indicated which Euler circle diagrams were appropriate with different quantifiers, and the results provided support both for conversion theory and for predictions derived from Grice's (1975. Syntax and Semantics, Vol. 3, Speech Acts. New York: Academic Press) theory of conversational implicatures. In Experiment 2, subjects carried out both an Euler circle task and an immediate inference task, followed by a test of syllogistic reasoning performance. It was found, surprisingly, that interpretational errors as determined using the Euler circle task showed no correlation with the same errors measured using an immediate inference task. It was concluded that performance on both these tasks can be affected by response biases, but that they are valid in certain contexts. Both conversion theory and Gricean theory were supported by the results of the syllogistic reasoning task, since subjects assessed as making these interpretational errors produced the predicted responses on this task.

Circle diagram representation of optical constants of metals and metal films

This work proposes the use of the trajectory of the optical admittance Y=iωϵ of metals and metal films on the complex plane as a comprehensive means of displaying their optical properties. The wavelength is changed from FIR to UV. When this convention is used, the contribution to Y from the conduction electrons and that from interband transitions appear as a semicircle and a full circle, respectively. This helps to visualize the interplay of each optical process in metals. Several examples are presented.

Quantitation of human shoulder anatomy for prosthetic arm control—II. Anatomy matrices

Part I presented mathematically continuous surfaces and origin-to-insertion centroidal trajectory data for the muscles of the human shoulder. Part II presents linear trajectory data for the same muscles, in addition to kinematic descriptions of the joints. ‘Anatomy’ matrices for musculature, which convert muscle forces (as estimated by cutaneously monitored EMG signals) to moments, within a prosthetic arm controller, are developed for both the linear and non-linear (centroidal) data, and then compared. Graphical analyses of the muscle functions are also presented via computer-generated ‘circle diagrams’.

Graphical Representation of Doubly Fed Induction Machine Operation

Abstract The transient state operation of doubly fed induction machine are described by complex variables. Then, circle diagrams are defined to show the variation of steady state currents under various conditions ; variation of torque is also shown from those diagrams. Such graphic aids help to understand the main features of doubly fed machines behavior.

Power Limits in Stepping and other Small Brushless Motors — A Simple Approach Using the Blondel Circle Diagram

Brushless drives are important, but are often thought to be difficult to treat quantitatively at the undergraduate level. The Blondel circle diagram is shown to be ideal for illuminating the steady-state behaviour and limitations of small brushless system, at a level suitable for undergraduate courses.

A microcomputer-based measurement system fordisplaying the admittance characteristics of acoustic transducers

The admittance circle diagram is an important method of characterising the terminal response and, thus, the electrical equivalent circuit of acoustic transducers. Equipment to yield such plots is relatively costly and consequently less readily available than might be desired. This paper describes a method of obtaining admittance plots, typically to frequencies of the order of a few megahertz, which involves only modest circuit development. The method avoids circuit design complexity by relying upon the computing power of any readily available microcomputer to effect correction of parameter cross-coupling.

Optical thickness monitoring sensitivity improvement using graphical methods

Semidirect level monitoring has error compensation capabilities of potential benefit to optical coatings of certain types. A review of the principles of level monitoring using circle diagrams shows how to design a level monitoring scheme for various cases, including the use of precoated monitoring chips. The film thickness sensitivities for various optical monitoring strategies differ considerably. Optimum level trigger point monitoring offers improved sensitivity of change in reflectance vs change in optical thickness. This procedure is also expected to give small thickness errors when optically monitored. Optimum level trigger point monitoring, and its application, is fully described.

Normalised high-speed performance analysis of small hybrid stepping motors

Despite the widespread use of hybrid stepping motors, the relationship between the parameters of the motor/drive combination and the steady-state capability is not widely understood. The steady-state behaviour of hybrid motors with constant-voltage variable-frequency supplies is analysed, using the Blondel circle diagram to illuminate the power conversion process, and identify the parameters which govern the maximum output power. It is shown that in spite of their apparent complexity, all hybrid motor/drive packages can be characterised by three simple parameters. This permits their theoretical steady-state performance to be displayed in the form of normalised operating point traces.

Relating instability in synchronous motors to steady-state theory using the Hurwitz-Routh criterion

Conditions under which spontaneous oscillations can occur in synchronous motors are evaluated in terms of normalised parameters. The method involves the development of the characteristic equation of the motor model in which viscous friction to ground or inertial damping is included. Application of the Hurwitz-Routh criterion to this equation reveals that a single dynamic stability boundary equation may be obtained within the region of ‘statically stable’ operation. The Hurwitz-Routh criterion is also shown to indicate the region of static instability. The findings are related directly to classical theory. In particular, when there is a complete absence of viscous friction, the dynamic stability boundary on the circle diagram of the motor is also shown to be circular. Experimental evidence is presented in support of the findings. The treatment is self-contained and should be within the scope of final-year undergraduates.

A Generalized Circle Diagram Approach for Global Analysis of Transmission System Performance

A Generalized Circle Diagram Approach for Global Analysis of Transmission System Performance

A Generalized Circle Diagram Approach For Global Analysis Of Transmission System Performance

The global response of a power system to variations in the node constraints is considered. The relation of specific system variables to independent node parameters is calculated using a numerical technique which provides a generalization of the elementary power circle diagram. Curves which show system performance during disturbances, tradeoffs between design parameters, voltage stability limits and multiple power flow solutions are produced. The theory of the method is presented through geometrical concepts, and its application is illustrated with several examples.

A circle diagram approach to the design of compensators

Abstract The paper presents a circle diagram approach to the design of compensators of single-input/single-output linear systems when a static error constant and dominant closed-loop poles are specified. This method can be applied to determine the transfer functions of both lead and lag compensators, and also to the design of two important cases: (1) with specified damping ratio, and (2) with specified settling time. Analytical relations can be used whenever the graphical accuracy is not satisfactory. A third-order system is considered as an example.

Dynamic braking performance of double-sided linear induction motors by circle diagram

Dynamic braking performance of double-sided linear induction motors by circle diagram

ASYNCHRONOUS PERFORMANCE OF HYSTERESIS MOTOR CONSIDERING EDDY-CURRENT EFFECTS

ABSTRACT A simplified model of the hysteresis motor is introduced, with eddy-current effects taken into consideration. The field analysis is based on Maxweell's equations; the output relations, such as forces, power and heat losses, are derived via Maxwell's stress tensor and Poynting's theorem, and a special variant of the circle diagram is proposed.

A Technique for Introducing Current Loci

A simple introductory approach to the circle diagram is presented. The desired current locus for a series R — X circuit is obtained with a minimum of algebraic diversion by commencing with Kirchhoff's Voltage Law. Resolution of an apparent contradiction to the student's logical sense is achieved by comparing two cartesian co-ordinate approaches to the mapping of W = 1/ S.