Universal Relations in Piezoelectric Composites With Eigenstress and Polarization Fields, Part II: Multiphase Media—Effective Behavior

1993 ◽  
Vol 60 (2) ◽  
pp. 270-275 ◽  
Author(s):  
Y. Benveniste
Keyword(s):  
Spontaneous Polarization ◽  
Binary Systems ◽  
Virtual Work ◽  
Companion Paper ◽  
Piezoelectric Composites ◽  
Piezoelectric Media ◽  
Electromechanical Loading ◽  
Dielectric Tensors ◽  
The Individual ◽  
Special Case

We consider heterogeneous piezoelectric media in general and multiphase piezoelectric composites in particular. A distribution of statistically homogeneous eigenstress and spontaneous polarization fields is admitted in the solid which is itself statistically homogeneous, and the effective eigenstress and spontaneous polarization is sought. The method here is based on the use of virtual work theorems in piezoelectric media and therefore differs from the approach used in the companion paper (Benveniste, 1993). We show that the effective eigenstress and polarization follow from a knowledge of the influence functions related to an electromechanical loading of the composite aggregate in which no eigenstresses and polarizations are present. When applied to the special case of binary systems with constant eigenstress and polarization fields in the phases, the above result implies that the effective eigenstress and polarization can be determined in terms of the effective elastic, piezoelectric, dielectric tensors of the medium, the constituent properties, and the individual eigenstresses and polarizations.

Universal Relations in Piezoelectric Composites With Eigenstress and Polarization Fields, Part I: Binary Media—Local Fields and Effective Behavior

1993 ◽  
Vol 60 (2) ◽  
pp. 265-269 ◽  
Author(s):  
Y. Benveniste
Keyword(s):  
Spontaneous Polarization ◽  
Electric Field Intensity ◽  
Local Fields ◽  
Composite Media ◽  
Piezoelectric Composites ◽  
Arbitrary Phase ◽  
Electromechanical Loading ◽  
Piezoelectric Behavior ◽  
Binary Composite ◽  
Effective Constants

Binary composite media of arbitrary phase geometry are considered. The constituent phases have general anisotropic piezoelectric behavior and contain constant eigenstress and spontaneous polarization fields. An electromechanical loading of the composite aggregate is found which results in uniform strain and electric field intensity throughout the solid. The existence of these uniform fields is used to derive exact universal relations between the local fields as well as between the effective constants of the composite aggregate.

Chemical Bonds Properties and Spontaneous Polarization of Orthogonal SrBi2Ta2O9 Crystals

2016 ◽  
Vol 848 ◽  
pp. 688-695
Author(s):  
Xiao Hong Xiao ◽  
Shi Chun Li
Keyword(s):  
Spontaneous Polarization ◽  
Cluster Structure ◽  
Chemical Bonds ◽  
Local Cluster ◽  
Valence Electron Density ◽  
Effective Valence ◽  
Individual Bond ◽  
Atomic Coordination ◽  
Experimental Values ◽  
The Individual

The bonds structure, atomic coordination situation and local cluster structure in SrBi2Ta2O9 were analyzed by means of the Atomic Environment Calculation (AEC), and then the SrBi2Ta2O9 crystal was decomposed into 20 pseudo-binary crystals with the crystal decomposition method. The chemical bonds properties, such as effective valence electron density and iconicity of the individual bond were calculated by the dielectric chemical bonds theory. And the correlation between chemical bonds properties and spontaneous polarization of the bismuth layered ferroelectrics was established. Finally, the spontaneous polarization in ferroelectric SrBi2Ta2O9 and other relevant ferroelectrics were calculated, which are in good agreement with the experimental values and other theoretical calculated values.

Calculation of Component Mode Synthesis Matrices From Measured Frequency Response Functions, Part 2: Application

1998 ◽  
Vol 120 (2) ◽  
pp. 509-516 ◽  
Author(s):  
J. A. Morgan ◽  
C. Pierre ◽  
G. M. Hulbert
Keyword(s):  
Frequency Response ◽  
Coupled System ◽  
Companion Paper ◽  
Component Mode Synthesis ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Measured Frequency ◽  
Measured Frequency Response ◽  
Coupled Beams ◽  
The Individual

This paper demonstrates how to calculate Craig-Bampton component mode synthesis matrices from measured frequency response functions. The procedure is based on a modified residual flexibility method, from which the Craig-Bampton CMS matrices are recovered, as presented in the companion paper, Part I (Morgan et al., 1998). A system of two coupled beams is analyzed using the experimentally-based method. The individual beams’ CMS matrices are calculated from measured frequency response functions. Then, the two beams are analytically coupled together using the test-derived matrices. Good agreement is obtained between the coupled system and the measured results.

Azimuthal sensitivity of neurons in primary auditory cortex of cats. II. Organization along frequency-band strips

1990 ◽  
Vol 64 (3) ◽  
pp. 888-902 ◽  
Author(s):  
R. Rajan ◽  
L. M. Aitkin ◽  
D. R. Irvine
Keyword(s):  
Spatial Distribution ◽  
Auditory Cortex ◽  
Frequency Band ◽  
Primary Auditory Cortex ◽  
Companion Paper ◽  
Significant Feature ◽  
Central Field ◽  
Cortical Surface ◽  
Peak Response ◽  
The Individual

1. The organization of azimuthal sensitivity of units across the dorsoventral extent of primary auditory cortex (AI) was studied in electrode penetrations made along frequency-band strips of AI. Azimuthal sensitivity for each unit was represented by a mean azimuth function (MF) calculated from all azimuth functions obtained to characteristic frequency (CF) stimuli at intensities 20 dB or more greater than threshold. MFs were classified as contrafield, ipsi-field, central-field, omnidirectional, or multipeaked, according to the criteria established in the companion paper (Rajan et al. 1990). 2. The spatial distribution of three types of MFs was not random across frequency-band strips: for contra-field, ipsi-field, and central-field MFs there was a significant tendency for clustering of functions of the same type in sequentially encountered units. Occasionally, repeated clusters of a particular MF type could be found along a frequency-band strip. In contrast, the spatial distribution of omnidirectional MFs along frequency-band strips appeared to be random. 3. Apart from the clustering of MF types, there were also regions along a frequency-band strip in which there were rapid changes in the type of MF encountered in units isolated over short distances. Most often such changes took the form of irregular, rapid juxtapositions of MF types. Less frequently such changes appeared to show more systematic changes from one type of MF to another type. In contrast to these changes in azimuthal sensitivity seen in electrode penetrations oblique to the cortical surface, much less change in azimuthal sensitivity was seen in the form of azimuthal sensitivity displayed by successively isolated units in penetrations made normal to the cortical surface. 4. To determine whether some significant feature or features of azimuthal sensitivity shifted in a more continuous and/or systematic manner along frequency-band strips, azimuthal sensitivity was quantified in terms of the peak-response azimuth (PRA) of the MFs of successive units and of the azimuthal range over which the peaks occurred in the individual azimuth functions contributing to each MF (the peak-response range). In different experiments shifts in these measures of the peaks in successively isolated units along a frequency-band strip were found generally to fall into one of four categories: 1) shifts across the entire frontal hemifield; 2) clustering in the contralateral quadrant; 3) clustering in the ipsilateral quadrant; and 4) clustering about the midline. In two cases more than one of these four patterns were found along a frequency-band strip.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Double-Peaked Flare Events on red Dwarf Stars and Solar ‘Sympathetic’ Flares

1976 ◽  
Vol 71 ◽  
pp. 475-475
Author(s):  
M. Rodonò
Keyword(s):  
Proximity Effect ◽  
Binary Systems ◽  
Angular Separation ◽  
Dwarf Stars ◽  
Multiple Systems ◽  
Photometric Observations ◽  
Red Dwarfs ◽  
Flare Stars ◽  
Red Dwarf Stars ◽  
The Individual

About 50% of the flare events observed on red dwarfs are at least double-peaked. As the majority of flare stars are members of double or multiple systems, the possibility that time-overlapping flares originate quasi-simultaneously on the individual components is discussed.Assuming a poissonian occurrence of flares in both components, the expected probability of observing double-peaked flares is lower than 1% for the most active binary systems.However, from photometric observations of the double flare star EQ Peg (BD +19°5116 AB) carried out by the author with an area scanner (the components' angular separation is 3.7″) about 20% of the observed flares have been found to be double-peaked flares resulting from separate flares, one in each component. A direct flare triggering of the following flare by the preceding one can be ruled out since the light travel-time between the two components is 3.5 h, while the observed time delay between the flare peaks is about 10 min. Moreover, the proximity effect does not seem to play an important triggering role.It is concluded that, although the analogy with solar ‘sympathetic’ flares is not always applicable, it is the most promising framework within which the majority of double-peaked flare events on red dwarfs must be interpreted.

Nonlinear Theory for Composite Laminated Shells With Interfacial Damage

1998 ◽  
Vol 65 (3) ◽  
pp. 711-718 ◽  
Author(s):  
Zhen-qiang Cheng ◽  
S. Kitipornchai
Keyword(s):  
Nonlinear Theory ◽  
Virtual Work ◽  
Shear Stresses ◽  
Interfacial Damage ◽  
Laminated Shells ◽  
Lines Of Curvature ◽  
Perfect Bonding ◽  
Transverse Shear Stresses ◽  
Bounding Surfaces ◽  
Special Case

Interfacial damage is incorporated in the proposed nonlinear theory. for composite laminated shells. A spring-layer model is employed to characterize damaged interfaces spanning from perfect bonding to different degrees of imperfect bonding in shear. By enforcing compatibility conditions for transverse shear stresses both at interfaces and on two bounding surfaces of a laminated shell, only five unknowns are needed for modeling its behavior. The principle of virtual work is used to derive the governing equations, which are of 14th order in lines of curvature coordinates, variationally self-consistent with seven prescribed boundary conditions. This theory includes the conventional higher-order zigzag model for a perfectly bonded shell as a special case. Numerical results provide a physical understanding of the effect of interracial damage on bending and buckling responses of composite laminated shells.

Improved Alignment Technique for Dish Concentrators

Solar Energy ◽  
2003 ◽  
Author(s):  
Charles E. Andraka ◽  
Richard B. Diver ◽  
K. Scott Rawlinson
Keyword(s):  
Focal Length ◽  
Electric Energy ◽  
Parabolic Systems ◽  
Companion Paper ◽  
Quantitative Information ◽  
Key Factors ◽  
Look Back ◽  
Parabolic Dish ◽  
The Individual

Parabolic dish concentrators have shown significant promise of generating competitive electric energy for grid and off-grid applications. The efficiency of a dish-electric system is strongly affected by the quality of the concentrator optics. Most parabolic systems consist of a number of facets mounted to a support structure in an approximate parabolic arrangement, where the individual facets have spherical or parabolic optical shapes. The individual facets must be accurately aligned because improper alignment can compromise performance or create hot spots that can reduce receiver life. A number of techniques have been used over the years to align concentrator facets. In the Advanced Dish Development System (ADDS) project, a color look-back alignment approach that accurately aligns facets (mirror panels) and in addition indicates quantitative information about the focal length was developed. Key factors influencing the alignment, some of which had very large effects on the quality of the alignment, were also identified. The influence of some of the key factors was characterized with a flux mapping system on the second-generation ADDS concentrator. Some of these factors also affect other alignment approaches. The approach was also successfully applied to two other concentrators with differing facet arrangements. Finally, we have extended the method to a 2-f approach that eliminates the need for a distant line-of-sight to the dish and permits alignment at near vertical dish attitudes. In this paper, we outline the color look-back alignment approach, discuss the key alignment factors and their effect on flux distribution, and discuss extensions to non-gore dishes. A companion paper discusses the 2-f color alignment approach in detail.

Distributed Systems

2020 ◽  
pp. 143-198
Author(s):  
Andreas Bolfing
Keyword(s):  
Distributed Systems ◽  
Fault Tolerant ◽  
Deterministic Algorithm ◽  
Impossibility Result ◽  
Software Systems ◽  
Trade Off ◽  
Byzantine Failures ◽  
The Individual ◽  
Special Case

Chapter 5 considers distributed systems by their properties. The first section studies the classification of software systems, which is usually distinguished in centralized, decentralized and distributed systems. It studies the differences between these three major approaches, showing there is a rather multidimensional classification instead of a linear one. The most important case are distributed systems that enable spreading of computational tasks across several autonomous, independently acting computational entities. A very important result of this case is the CAP theorem that considers the trade-off between consistency, availability and partition tolerance. The last section deals with the possibility to reach consensus in distributed systems, discussing how fault tolerant consensus mechanisms enable mutual agreement among the individual entities in presence of failures. One very special case are so-called Byzantine failures that are discussed in great detail. The main result is the so-called FLP Impossibility Result which states that there is no deterministic algorithm that guarantees solution to the consensus problem in the asynchronous case. The chapter concludes by considering practical solutions that circumvent the impossibility result in order to reach consensus.

scholarly journals Observational Evidence for Mass Exchange in Close Binary Systems

1977 ◽  
Vol 42 ◽  
pp. 371-382
Author(s):  
Horst Drechsel ◽  
Jürgen Rahe ◽  
Gudrun Wolfschmidt ◽  
Yoji Kondo ◽  
George E. McCluskey
Keyword(s):  
Northern Hemisphere ◽  
Mass Exchange ◽  
Binary Systems ◽  
Variable Stars ◽  
Observational Evidence ◽  
Close Binary ◽  
Wide Angle ◽  
Close Binary Systems ◽  
The Individual

In 1925 a photographic search for new variable stars was begun at the Remeis-Observatory in Bamberg. Initially the sky patrol covered only the northern hemisphere, but in 1964 it was also extended to the southern sky. At the individual observing stations, the sky is systematically photographed with several wide-angle patrol cameras which are attached to the same mounting, and which have f/6 Tessar lenses of 4-inch aperture. Each camera covers a 13-by-13 degree field. The plates are usually exposed for one hour and a photographic magnitude of 14m is reached.

scholarly journals Origin of Binary Systems

1992 ◽  
Vol 151 ◽  
pp. 9-19
Author(s):  
Peter Bodenheimer
Keyword(s):  
Angular Momentum ◽  
Binary Systems ◽  
Theoretical Calculations ◽  
Pressure Effects ◽  
Close Binaries ◽  
Rotating Stars ◽  
Multiple Systems ◽  
The Individual ◽  
Protostellar Collapse ◽  
Three Body

Recent observational studies of the properties of binary systems among young stars indicate that the majority of binaries are formed very early in the history of a star, perhaps during the protostellar collapse. Major observational facts to be explained include the overall binary frequency, the non-negligible occurrence of multiple systems, and the distributions of period, eccentricity, and mass ratio among the individual binaries. Theoretical calculations of the collapse of rotating protostars during the isothermal phase indicate instability to fragmentation into multiple systems. This process in general produces systems with periods greater than a few hundred years, although somewhat shorter periods are possible. Fragmentation during later, optically thick, phases of collapse tends to be suppressed by pressure effects. Therefore, major theoretical problems remain concerning the origin of close binaries. Fission of rapidly rotating stars, tidal capture, and three-body capture have been shown to be improbable mechanisms for formation of close binaries. Mechanisms currently under study include gravitational instabilities in disks, orbital interactions and disk-induced captures in fragmented multiple systems, hierarchical fragmentation, and orbital decay of long-period systems. Single stars, on the other hand, could result by escape from multiple systems or by the collapse of clouds of low angular momentum, coupled with angular momentum transport after disk formation.

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