• Title, Summary, Keyword: frequency loci

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Mode localization and frequency loci veering in an aircraft with external stores

  • Liu, J.K.;Chan, H.C.
    • Structural Engineering and Mechanics
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    • v.8 no.2
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    • pp.181-191
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    • 1999
  • This paper presents an investigation of the mode localization and frequency loci veering phenomena in an aircraft with disordered external stores. Two theoretical analyses are carried out to study the occurring mechanism of the two phenomena: condensation technique in the subspace spanned by modes of interest and geometric mapping theory in the complex plane. Two simple criteria for predicting the occurrence of the mode localization and frequency loci veering are put forward. The prediction of the phenomena by our theoretically proposed criteria is in good agreement with that obtained through numerical calculations of characteristic solutions of the disordered system.

Mode localization and frequency loci veering in a disordered coupled beam system

  • Lu, Z.R.;Liu, J.K.;Huang, M.
    • Structural Engineering and Mechanics
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    • v.24 no.4
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    • pp.493-508
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    • 2006
  • Vibration mode localization and frequency loci veering in disordered coupled beam system are studied in this paper using finite element analysis. Two beams coupled with transverse and rotational springs are examined. Small disorders in the physical parameters such as Young's modulus, mass density or span length of the substructure are introduced in the investigation of the mode localization and frequency loci veering phenomena. The effect of disorder in the elastic support on the mode localization phenomenon is also discussed. It is found that an asymmetric disorder in the weakly coupled system will lead to the occurrence of mode localization and frequency loci phenomena.

Prevalence of negative frequency-dependent selection, revealed by incomplete selective sweeps in African populations of Drosophila melanogaster

  • Kim, Yuseob
    • BMB Reports
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    • v.51 no.1
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    • pp.1-2
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    • 2018
  • Positive selection on a new beneficial mutation generates a characteristic pattern of DNA sequence polymorphism when it reaches an intermediate allele frequency. On genome sequences of African Drosophila melanogaster, we detected such signatures of selection at 37 candidate loci and identified "sweeping haplotypes (SHs)" that are increasing or have increased rapidly in frequency due to hitchhiking. Based on geographic distribution of SH frequencies, we could infer whether selective sweeps occurred starting from de novo beneficial mutants under simple constant selective pressure. Single SHs were identified at more than half of loci. However, at many other loci, we observed multiple independent SHs, implying soft selective sweeps due to a high beneficial mutation rate or parallel evolution across space. Interestingly, SH frequencies were intermediate across multiple populations at about a quarter of the loci despite relatively low migration rates inferred between African populations. This invokes a certain form of frequency-dependent selection such as heterozygote advantage. At one locus, we observed a complex pattern of multiple independent that was compatible with recurrent frequency-dependent positive selection on new variants. In conclusion, genomic patterns of positive selection are very diverse, with equal contributions of hard and soft sweeps and a surprisingly large proportion of frequency-dependent selection in D. melanogaster populations.

Vibration Analysis of Rotating Composite Cantilever Plates

  • Kim, Sung-Kyun;Yoo, Hong-Hee
    • Journal of Mechanical Science and Technology
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    • v.16 no.3
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    • pp.320-326
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    • 2002
  • A modeling method for the vibration analysis of rotating composite cantilever plates is presented in this paper. The coupling effects between inplane motions and the bending motion are considered and explicit mass and stiffness matrices are derived for the modal analysis. Numerical results are obtained and some of them are compared to those of a commercial program to confirm the accuracy of the present method. Numerical results show that the coupling effects become important only when laminates are stacked up unsymmetrically. Incidentally, natural frequencies loci veering, loci crossing, and associated mode shape variations are observed.

On mode localization of a weakly coupled beam system with spring-mass attachments

  • Huang, M.;Liu, J.K.;Lu, Z.R.
    • Structural Engineering and Mechanics
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    • v.42 no.1
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    • pp.13-24
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    • 2012
  • There are a large number of papers in the literature dealing with the free vibration analysis of single/multi-span uniform beam with multiple spring-mass systems, but that of coupled multi-span beams carrying spring-mass attachments is rare. In this note, free vibration analysis of a weakly coupled beam system with spring-mass attachments is conducted. The mode localization and frequency loci veering phenomena of the coupled beam system are investigated. Studies show that for weakly coupled beam system with spring-mass attachments, the mode localization and frequency loci veering will occur once there is a disorder in the system.

Mode localization and veering of natural frequency loci in two circular plates coupled with a fluid

  • Jeong, Kyeong-Hoon
    • Structural Engineering and Mechanics
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    • v.22 no.6
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    • pp.719-739
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    • 2006
  • An analytical method for the free vibration of two circular plates coupled with an inviscid and compressible fluid is developed by the Rayleigh-Ritz method. The fluid is bounded by a rigid cylindrical vessel and two circular plates with an unequal thickness and diameter. It was found that the theoretical results could predict well the fluid-coupled natural frequencies with an excellent accuracy when compared with the finite element analysis results. As the fluid thickness increases or the plate thickness difference increases, an abrupt curve veering in the natural frequency loci of the neighboring modes and drastic changes in the corresponding mode shapes are observed. The mode localization frequently appears in the higher modes and in the wide gap between the plates because of a decrease in the fluid coupling owing to the fluid dispersion effect.

A Comparative Study on the Occurrence Loci of Disfluency between Neurogenic and Developmental Stuttering (신경인성과 발달성 말더듬의 비유창성 발생 자리에 대한 연구)

  • Shin, Myung-Sun;Kwon, Do-Ha;Yoon, Chi-Yeon
    • Speech Sciences
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    • v.13 no.3
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    • pp.185-195
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    • 2006
  • This study aims to clarify disfluency loci in a neurogenic stuttering group and to examine how the characteristics are different from a developmental stuttering group. For the study, spoken language samples were collected from 11 adults with developmental stuttering and 11 adults with neurogenic stuttering in the course of speaking tasks including reading, monologue and conversation. Using the collected samples, disfluency characteristics of the two groups were to be investigated by analyzing adaptation effect, consistency effect and frequency of disfluency occurrence according to word position, which are related to the occurrence loci of disfluency. Results of this study were as follows: First, while the neurogenic stuttering group did not show any adaptation effect, the developmental stuttering group showed the adaptation effect that the percent of disfluency word reducing as they read the same materials repeatedly. Second, there was no meaningful difference of consistency effect between the two stuttering groups. Third, the neurogenic stuttering group showed more disfluency frequency in final sounds among the word position compared to the developmental stuttering group.

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Ethnic Differences in Allelic Frequencies of Two (CA)n Microsatellite Markers Located on Chromosome 5q

  • Hong, Sung-Soo;Chae, Jae-Jin;Goh, Sung-Ho;Yong, Koong-Nam;Lee, Chung-Choo
    • Animal cells and systems
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    • v.1 no.1
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    • pp.123-128
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    • 1997
  • The characteristics of allelic polymorphisms of the two (CA)n microsatellite (p599 and ㅅ599) markers spanning the long arm of chromosome 5 were studied in 52 DNA samples from unrelated inhabitants of Seoul (Korea) by using the polymerase chain reaction (PCR) to investigate differences in allele frequencies between Korean and Caucasian populations. The 6 alleles were observed for p599 (CA)n with a polymorphism informative content (PIC) value of 0.71 and 9 alleles for ㅅ599 (CA)n with a PIC value of 0.82. The observed heterozygote frequencies of the loci were estimated to 0.730 and 0.846, respectively. Several allele frequencies of two loci showed significant differences between Korean and Caucasian populations. Genotype data from the two loci were consistent with the Hardy-Weinberg equilibrium by x2 test. Linkage disequilibrium between p599 (CA)n and ㅅ599 (CA)n loci was observed in x2 test between the observed and expected frequency of allelic association. The probability of matching calculated at each locus was 0.104 for p599 (CA)n and 0.043 for ㅅ599 (CA)n, respectively. These results demonstrate the need to determine populationspecific allele frequency distributions for polymorphic markers when performing genetic linkage studies in racially defined several populations.

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A calculation method of root loci band and its applications to robust control system design

  • Okuyama, Yoshifumi;Chen, Hong;Takemori, Fumiaki
    • 제어로봇시스템학회:학술대회논문집
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    • pp.350-353
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    • 1994
  • This paper presents a method to calculate the characteristic root areas and loci band of control systems with uncertainties. First, equations of boundary curves of root areas in the case of additive and multiplicative perturbation are derived. Then, an algorithm for the calculation of the array of closed curves is presented. When the upper bound of the absolute values of frequency responses for the uncertain part, is also frequency-dependent, the frequency-dependent, terms are included in the characteristic equation of the nominal system. This lead to the boundary equations of the root, areas for control systems with frequency-dependent uncertainty. Numerical examples of the control systems with multiplicative perturbations including frequency-dependent terms are presented to verify this calculation method. Finally, its applications to the design of robust control systems, e.g., passive adaptive control systems are also discussed.

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Molecular Characterisation of Nilagiri Sheep (Ovis aries) of South India Based on Microsatellites

  • Girish, Haris;Sivaselvam, S.N.;Karthickeyan, S.M.K.;Saravanan, R.
    • Asian-Australasian Journal of Animal Sciences
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    • v.20 no.5
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    • pp.633-637
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    • 2007
  • Genetic variation in Nilagiri sheep, the only apparel wool breed in South India was studied using 25 FAO recommended ovine-specific microsatellite markers. The number of observed alleles ranged from 3 to 8 with a mean of 5 across all loci. The size of alleles ranged from 72 to 228 bp. The frequency of alleles ranged from 0.0104 to 0.5781. In total, 125 alleles were observed at the 25 loci studied. The effective number of alleles ranged from 2.18 to 6.49. The mean number of effective alleles was 3.84 across all loci. All the 25 loci were found to be highly polymorphic. The PIC values ranged from 0.4587 to 0.8277 with a mean of 0.6485. Of 25 microsatellites studied, 17 were in Hardy-Weinberg Equilibrium proportions. The observed heterozygosity ranged from 0.4222 to 1.000 with a mean value of 0.7610 whereas the expected heterozygosity ranged from 0.5415 to 0.8459 with a mean value of 0.7213. Except six loci, the other loci revealed negative within-population inbreeding estimates (FIS) indicating excess of heterozygotes in the population of Nilagiri sheep.