Complete and Simplified Models for Estimating Vibration Instability of Cyclically Symmetric Ring Structures: Comparison and Verification

2018 ◽  
Vol 13 (3) ◽  
Author(s):  
Shiyu Wang ◽  
Penghui Zhang ◽  
Wenjia Sun
Keyword(s):  
Strong Support ◽  
Complete Model ◽  
Simplified Models ◽  
Weak Support ◽  
Fixed Frame ◽  
Ring Structures ◽  
Sample Structure ◽  
Classical Vibration ◽  
Time Invariant ◽  
Rotating Load

In-plane vibration of cyclically symmetric ring structures is examined with emphasis on the comparison of instabilities estimated by complete and simplified models. The aim of this paper is to understand under what conditions and to what degree the simplified models can approach the complete model. Previous studies develop time-variant models and employ perturbation method by assuming weak support. This work casts the rotating-load problem into a nonrotating load problem. A complete model with time-invariant coefficients is developed in rotating-support-fixed frame, where the bending and extensional deformations are incorporated. It is then reduced into two simplified ones based on different deformation restrictions. Due to the time-invariant effect observed in the rotating-support-fixed frame, the eigenvalues are formulated directly by using classical vibration theory and compared based on a sample structure. The comparisons verify that the two types of models are comparable only for weak support. Furthermore, the simplified models cannot accurately predict all unstable behaviors in particular for strong support. The eigenvalues are different even in comparable regions. For verification purpose, the time-invariant models are transformed into time-variant ones in the inertial frame, based on which instabilities are estimated by using Floquét theory. Consistence between the time-invariant and -variant models verifies the comparisons.

Natural frequency splitting and principal instability of rotating cyclic ring structures

2016 ◽  
Vol 232 (1) ◽  
pp. 66-78 ◽  
Author(s):  
Wenjia Sun ◽  
Shiyu Wang ◽  
Ying Xia ◽  
Penghui Zhang
Keyword(s):  
Natural Frequency ◽  
Analytical Method ◽  
Parametric Instability ◽  
Classical Problem ◽  
Elastic Model ◽  
Frequency Splitting ◽  
Fixed Frame ◽  
Equivalent Time ◽  
Ring Structures ◽  
Time Invariant

This work develops an analytical method to estimate the natural frequency splitting and principal instability of the rotating cyclic ring structures. An elastic model is built up under the ring-fixed frame by using the energy method. The modeling leads to a partial differential equation with time-variant coefficient. The eigenvalue is formulated to estimate the natural frequency splitting, principal instability and their relationships. The dependence of the basic parameters on the natural frequency splitting and principal instability is demonstrated. The principal instability can occur at the splitting natural frequencies but cannot at the repeating ones. A classical problem regarding the parametric instability of the rotating ring with stationary supports and the inverse problem are examined. The results verify that the natural frequency splitting does not mean unstable for the former problem, but for the latter the splitting implies unstable. Besides, the model is transformed into the support-fixed frame and thus an equivalent time-invariant model is obtained, which is solved by using the general vibration theory. The analytical method is validated through the comparisons with the results in the open literature and especially the comparisons between the results from the two types of frames.

Comparison of complete and simplified models in terms of eigenvalues of cyclically symmetric ring structures

2017 ◽  
Vol 24 (19) ◽  
pp. 4449-4464 ◽  
Author(s):  
Shiyu Wang ◽  
Penghui Zhang ◽  
Wenjia Sun
Keyword(s):  
Closed Form ◽  
Time Evolution ◽  
Parametric Instability ◽  
Ring Structure ◽  
Stiffness Ratio ◽  
Complete Model ◽  
Simplified Models ◽  
Parametric Vibrations ◽  
Direct Perturbation ◽  
Ring Structures

This work examines the free and parametric vibrations of constrained cyclically symmetric ring structures and compares the restrictions from different modeling assumptions. A complete model and two simplified models are developed by introducing different restrictions on deflections. The eigenvalues are formulated by direct perturbation and mode superposition. The results verify that they are comparable on the condition that the stiffness ratio of the rotating support to ring bending is relatively small. The eigenvalue splitting, parametric instability and their relationships are determined in closed form. The simplified models can correctly predict the splitting behavior before or after the loci veering. Two types of models obtain the same rules governing the instability, but the simplified models cannot accurately approach the time-evolution of the instability. Hence, it needs to be cautious to use the simplified models to estimate the instability behaviors for a cyclically symmetric ring structure with larger stiffness ratios especially within the loci veering range. Main results are verified by numerical calculations.

The Demand For Money in Pakistan: Reply (Notes and Comments)

1975 ◽  
Vol 14 (3) ◽  
pp. 370-375
Author(s):  
M. A. Akhtar
Keyword(s):  
Interest Rates ◽  
Money Demand ◽  
Strong Support ◽  
Physical Capital ◽  
Careful Examination ◽  
Demand For Money ◽  
Weak Support ◽  
Complementarity Hypothesis ◽  
The Difference ◽  
The One

I am grateful to Abe, Fry, Min, Vongvipanond, and Yu (hereafter re¬ferred to as AFMVY) [1] for obliging me to reconsider my article [2] on the demand for money in Pakistan. Upon careful examination, I find that the AFMVY results are, in parts, misleading and that, on the whole, they add very little to those provided in my study. Nevertheless, the present exercise as well as the one by AFMVY is useful in that it furnishes us with an opportunity to view some of the fundamental problems involved in an empi¬rical analysis of the demand for money function in Pakistan. Based on their elaborate critique, AFMVY reformulate the two hypo¬theses—the substitution hypothesis and the complementarity hypothesis— underlying my study and provide us with some alternative estimates of the demand for money in Pakistan. Briefly their results, like those in my study, indicate that income and interest rates are important in deter¬mining the demand for money. However, unlike my results, they also suggest that the price variable is a highly significant determinant of the money demand function. Furthermore, while I found only a weak support for the complementarity between money demand and physical capital, the results obtained by AFMVY appear to yield a strong support for that rela¬tionship.1 The difference in results is only a natural consequence of alter¬native specifications of the theory and, therefore, I propose to devote most of this reply to the criticisms raised by AFMVY and the resulting reformulation of the two mypotheses.

scholarly journals Molecular Evolution of Phototransduction Pathway Genes in Nocturnal and Diurnal Fireflies (Coleoptera: Lampyridae)

Insects ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 561
Author(s):  
Gavin J. Martin ◽  
Sarah E. Lower ◽  
Anton Suvorov ◽  
Seth M. Bybee
Keyword(s):  
Positive Selection ◽  
Transient Receptor Potential ◽  
Strong Support ◽  
Model Organism ◽  
Receptor Potential ◽  
Guanine Nucleotide Binding Protein ◽  
Weak Support ◽  
Niche Adaptation ◽  
Ideal System ◽  
Phototransduction Pathway

Most organisms are dependent on sensory cues from their environment for survival and reproduction. Fireflies (Coleoptera: Lampyridae) represent an ideal system for studying sensory niche adaptation due to many species relying on bioluminescent communication; as well as a diversity of ecologies. Here; using transcriptomics; we examine the phototransduction pathway in this non-model organism; and provide some of the first evidence for positive selection in the phototransduction pathway beyond opsins in beetles. Evidence for gene duplications within Lampyridae are found in inactivation no afterpotential C and inactivation no afterpotential D. We also find strong support for positive selection in arrestin-2; inactivation no afterpotential D; and transient receptor potential-like; with weak support for positive selection in guanine nucleotide-binding protein G(q) subunit alpha and neither inactivation nor afterpotential C. Taken with other recent work in flies; butterflies; and moths; this represents an exciting new avenue of study as we seek to further understand diversification and constraint on the phototransduction pathway in light of organism ecology.

Generations and Aging: A Longitudinal Study

1975 ◽  
Vol 6 (2) ◽  
pp. 85-101 ◽  
Author(s):  
Jay Meddin
Keyword(s):  
Longitudinal Study ◽  
Survey Data ◽  
Age Differences ◽  
Secondary Analysis ◽  
Strong Support ◽  
Weak Support ◽  
Theories Of Aging ◽  
Longitudinal Investigation ◽  
Values And Beliefs ◽  
The Relationship

This study is a longitudinal investigation of the relationship between age and subjective outlook. Over the years, a number of theoretical positions have been introduced to either account for or to minimize age differences in attitudes, values and beliefs. The author has organized these theories of aging into three basic sociological frameworks or models: the “generations” model, the “age status” model and the “illusion of differences” model. Using a relatively simple methodological design, hypotheses derived from these models were tested through secondary analysis of survey data. Strong support was found for the “generations” hypothesis, weak support for the “age status” hypothesis, and no support at all for the “illusion of differences” hypothesis.

Local Weak Support Effect on the Stability of Surrounding Rocks in Deep Roadway

2014 ◽  
Vol 945-949 ◽  
pp. 1232-1235 ◽  
Author(s):  
Wei Jun Hu ◽  
Hua Cheng
Keyword(s):  
High Stress ◽  
Strong Support ◽  
Support Effect ◽  
Simulation Software ◽  
Maintenance Cost ◽  
Related Research ◽  
Weak Support ◽  
Software Analysis ◽  
Mine Roadway ◽  
The Stability

Coal mine roadway roof and sides often take strong support, and the floor support is weak or none support. Because of the high stress, roadway damage phenomena have occurred often, take reasonable repair plan is the key to the recovery project. Reasonable repair plan not only can effectively control the deformation of surrounding rocks, but also can reduce the maintenance cost. According to the surrounding rocks’ property and depth of roadway in Anhui Huainan Pan-III mine, using FLAC3D numerical simulation software, analysis of the effect on plastic zone, surrounding rocks stress and displacement under different floor support, and put forward the repair plan to this coal, the related research conclusions can provide reference for design and construction to similar engineering.

Asymmetrically distorted structures of monosilacyclobutane and disilacyclobutane radical cations studied by ab initio and density functional theories

2012 ◽  
Vol 90 (7) ◽  
pp. 584-596
Author(s):  
Z.J. Cai ◽  
Y.J. Shi
Keyword(s):  
Ab Initio ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Strong Support ◽  
Electronic States ◽  
Radical Cations ◽  
Ring Structure ◽  
The Other ◽  
Significant Difference ◽  
Ring Structures

The geometrical and electronic structures of a series of six monosilacyclobutane and 1,3-disilacyclobutane radical cations were systematically studied using ab initio and density functional theories. It was shown that all six radical cations possess an asymmetrically distorted structure in their ground electronic states. In the asymmetrically distorted C1 structure of monosilacyclobutane cations, one Si–C bond was elongated and the other was shortened. For the disilacyclobutane cations, two ring bonds were elongated and the other two contracted. The asymmetrical distortion was enhanced by exocyclic methyl substitutions and weakened by endocyclic Si substitution. The unpaired electron was localized mainly in the elongated σ(Si–C) ring bond(s) in all six cations. Studies of the excited electronic states of the cations provided strong support that the asymmetrical distortion in the four-membered-ring cations originates from the second-order Jahn–Teller effect. It was found that the puckered ring structures in the monosilacyclobutane molecules were maintained upon ionization, whereas 1,3-disilacyclobutane cations changed to a planar ring structure. Examination of the potential energy surfaces of all six cations showed that the Si–C ring bond elongation is the main contributor to the significant difference in the geometry change between monosilacyclobutane and disilacyclobutane species upon ionization.

Integrating multiple sources of data on migratory timing and catchability to estimate escapement for steelhead trout (Oncorhynchus mykiss)

2007 ◽  
Vol 64 (8) ◽  
pp. 1101-1115 ◽  
Author(s):  
Josh Korman ◽  
Caroline C Melville ◽  
Paul S Higgins
Keyword(s):  
Oncorhynchus Mykiss ◽  
Strong Support ◽  
Steelhead Trout ◽  
Multiple Sources ◽  
Weak Support ◽  
Life Data ◽  
Spawning Behaviour ◽  
Median Date ◽  
Gender Based ◽  
And Gender

We evaluated the influence of biological, physical, and year effects on catchability, survey life, and departure timing for a winter-run steelhead (Oncorhynchus mykiss) population and compared the performance of alternate escapement models. Date of entry and gender explained 65% of the variability in survey life, and there was no evidence for differences in survey life among years. The median date of departure for male spawners occurred 2 weeks later relative to females, and a gender-based departure model was strongly supported. Departure timing was significantly different among years (p < 0.05), but the maximum difference in median departure dates was only 11 days. The ratio of horizontal visibility to discharge explained 50% of the variation in catchability, and there was weak support for a model that accounted for effects associated with courtship and spawning behaviour. There was strong support for an escapement model that assumed survey life and catchability relationships were common among years. Joint use of departure timing and survey life data reduced uncertainty in escapement estimates by an average of 40%. The major advantage of our escapement model is that it increases the precision of estimates while avoiding the use of overly simplistic assumptions about run timing and catchability.

scholarly journals Population structures of Astragalus filipes collections from western North America

Botany ◽  
2010 ◽  
Vol 88 (6) ◽  
pp. 565-574 ◽  
Author(s):  
B. Shaun Bushman ◽  
Kishor Bhattarai ◽  
Douglas A. Johnson
Keyword(s):  
Genetic Diversity ◽  
British Columbia ◽  
North America ◽  
Genetic Correlations ◽  
Geographic Distance ◽  
Strong Support ◽  
Structured Populations ◽  
Weak Support ◽  
Population Structures ◽  
Distance Matrices

The majority of species used for revegetation in semi-arid western rangelands of North America are grasses, with few forbs and nearly no legumes. Astragalus filipes (Torr. Ex A. Gray) is a western North American legume and a promising candidate for use in rangeland revegetation, but assessments of plant species diversity and structure are necessary to determine which collections should be used to constitute a conservation unit or regional seed source. To address this issue, we characterized within-collection genetic diversity, identified genetically differentiated groups, and tested genetic correlations with environmental variables on 67 collections of A. filipes. Within-population genetic diversity was greatest for collections in Oregon and lowest for collections in British Columbia and central Nevada. Five genetically differentiated groups were detected: one with strong support from central Nevada, one with strong support from British Columbia, and three with weak support comprising all other collections throughout Oregon, Washington, California, Idaho, and Nevada. Although there was significant correlation between genetic and linear geographic distance matrices, there was no correlation between genetic and phenotypic, elevation, temperature, or precipitation distance matrices. These results show that geographic distance contributes to genetic differentiation, and that structured populations have occurred in northernmost and southernmost groups of collections of A. filipes.

Social status, types of family interaction and educational styles

1992 ◽  
Vol 33 (2) ◽  
pp. 308-325 ◽  
Author(s):  
Jean Kellerhals ◽  
Cléopâtre Montandon ◽  
Gilbert Ritschard
Keyword(s):  
Middle Class ◽  
Strong Support ◽  
Lower Class ◽  
Class Groups ◽  
Parent Child Relationship ◽  
Weak Support ◽  
Child Relationship ◽  
Established Fact ◽  
Strong Control ◽  
Clear Relation

It is A well-established fact that families vary quite widely in their educational practices. In the past twenty years a certain number of studies on socialization have revealed a clear relation between the socioeconomic status of the parents and their educational style. Kohn (1977), for example, has shown that the emphasis parents put on discipline and immediate conformity is more pronounced in lower-class groups, whereas middle class groups value more the internalization of instructions and the development of personal motivations. In the same vein, psychologists and social psychologists have observed that the ‘authoritarian’ style of parent-child relationship (consisting of strong control and weak support) prevails more often in lower-class groups than in middle class groups, the latter being more prone to exercise strong support combined with marked control in their child's education (Bronfenbrenner 1958). Family sociologists have produced quite exhaustive articles covering the literature in this field (Gecas 1979; Peterson and Rollins 1987).

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