Relevant bibliographies by topics / Unbalanced sex ratio

Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers

Academic literature on the topic 'Unbalanced sex ratio'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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Journal articles on the topic "Unbalanced sex ratio"

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Paini, Dean R., and Winston J. Bailey. "Seasonal sex ratio and unbalanced investment sex ratio in the Banksia bee Hylaeus alcyoneus." Ecological Entomology 27, no. 6 (November 13, 2002): 713–19. http://dx.doi.org/10.1046/j.1365-2311.2002.00459.x.

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XING, Cai, Xi ZHANG, and Jian-Lin NIU. "The Effect of Unbalanced Sex Ratio on Human Behavior." Advances in Psychological Science 20, no. 10 (June 14, 2013): 1679–89. http://dx.doi.org/10.3724/sp.j.1042.2012.01679.

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Manzur, A., I. Cárdenas, R. Macaya, C. Almendra, G. Gajardo, M. Bianchi, and G. Durruty. "Unbalanced sex ratio in newborns obtained by intrauterine inseminations." International Congress Series 1271 (September 2004): 341–44. http://dx.doi.org/10.1016/j.ics.2004.06.021.

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Poston, Dudley L., Eugenia Conde, and Bethany DeSalvo. "China's unbalanced sex ratio at birth, millions of excess bachelors and societal implications." Vulnerable Children and Youth Studies 6, no. 4 (December 2011): 314–20. http://dx.doi.org/10.1080/17450128.2011.630428.

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Kempenaers, Bart. "Polygyny in the blue tit: unbalanced sex ratio and female aggression restrict mate choice." Animal Behaviour 47, no. 4 (April 1994): 943–57. http://dx.doi.org/10.1006/anbe.1994.1126.

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Janzen, Fredric J., David M. Delaney, Timothy S. Mitchell, and Daniel A. Warner. "Do Covariances Between Maternal Behavior and Embryonic Physiology Drive Sex-Ratio Evolution Under Environmental Sex Determination?" Journal of Heredity 110, no. 4 (April 15, 2019): 411–21. http://dx.doi.org/10.1093/jhered/esz021.

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Abstract Fisherian sex-ratio theory predicts sexual species should have a balanced primary sex ratio. However, organisms with environmental sex determination (ESD) are particularly vulnerable to experiencing skewed sex ratios when environmental conditions vary. Theoretical work has modeled sex-ratio dynamics for animals with ESD with regard to 2 traits predicted to be responsive to sex-ratio selection: 1) maternal oviposition behavior and 2) sensitivity of embryonic sex determination to environmental conditions, and much research has since focused on how these traits influence offspring sex ratios. However, relatively few studies have provided estimates of univariate quantitative genetic parameters for these 2 traits, and the existence of phenotypic or genetic covariances among these traits has not been assessed. Here, we leverage studies on 3 species of reptiles (2 turtle species and a lizard) with temperature-dependent sex determination (TSD) to assess phenotypic covariances between measures of maternal oviposition behavior and thermal sensitivity of the sex-determining pathway. These studies quantified maternal behaviors that relate to nest temperature and sex ratio of offspring incubated under controlled conditions. A positive covariance between these traits would enhance the efficiency of sex-ratio selection when primary sex ratio is unbalanced. However, we detected no such covariance between measures of these categories of traits in the 3 study species. These results suggest that maternal oviposition behavior and thermal sensitivity of sex determination in embryos might evolve independently. Such information is critical to understand how animals with TSD will respond to rapidly changing environments that induce sex-ratio selection.
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Servan, J., P. Zaborski, M. Dorizzi, and C. Pieau. "Female-biased sex ratio in adults of the turtle Emys orbicularis at the northern limit of its distribution in France: a probable consequence of interaction of temperature with genotypic sex determination." Canadian Journal of Zoology 67, no. 5 (May 1, 1989): 1279–84. http://dx.doi.org/10.1139/z89-182.

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Adult sex ratio in the turtle Emys orbicularis was determined in populations from seven ponds in Brenne (Indre, France). In all populations, the sex ratio was biased toward females. Among 290 captured animals, the male:female ratio was close to 0.5. Among different demographic factors that could affect the adult sex ratio, the most influential was probably the sex ratio of hatchlings. In Emys orbicularis, a ZZ male/ZW female system of genotypic sex determination has been postulated. Moreover, gonad differentiation is dependent on temperature and sex-reversed individuals can occur. To evaluate the importance of sex reversal among adult females, the blood of 78 animals was typed for the serologically detectable H-Y antigen, used as a tool to identify sexual genotype. In 73 of them, the H-Y phenotype was positive, conforming with female genotype, but in the other 5 females, it was negative (as in genotypic males), revealing that the sexual phenotype of these animals had been inverted. As the percentage of these sex-reversed genotypic males is low, the influence of temperature would appear not to be the sole cause of the observed unbalanced sex ratio. The female bias can be partly explained by the interaction of temperature with the ZZ/ZW system of genotypic sex determination. Indeed, in this system, sexual inversion under the influence of an epigenetic factor increases the ratio of genotypic females (ZW and WW) in the progeny.
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de Almeida, João Paulo Felix Augusto, Robson Guimarães dos Santos, and Tamí Mott. "Sex ratios and natal origins of green turtles from feeding grounds in the Southwest Atlantic Ocean." ICES Journal of Marine Science 78, no. 5 (May 19, 2021): 1840–48. http://dx.doi.org/10.1093/icesjms/fsab093.

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Abstract Potential effects of climate change on living species are a widely debated topic. Species with temperature-dependent sex determination can be particularly impacted by warmer temperatures because unbalanced sex ratios could threaten population viability. In sea turtles, sex ratio estimates have highlighted the potential feminization of current populations, which tends to increase since warmer temperatures would generate more females. Here, we evaluated temporal variation in sex ratios of green turtles from feeding grounds of the Southwest Atlantic Ocean (SWA) using data from a 7-year time frame, from 2010 to 2016. We also evaluated natal origins of female and male green turtles from SWA based on mitochondrial DNA. Sex ratios of juvenile and adult green turtles were generally female-skewed across collection years. We identified 11 haplotypes in northeast SWA, and the haplotype composition of females and males was slightly different. Likewise, the estimated the natal origins of females and males were divergent. Ascension Island was estimated to be the main source of females while Guinea Bissau was estimated to be the main source of males. Studies evaluating natal origins of females and males independently are rare, this study provides one of the first assessments of the kind for green turtles in the SWA.
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Aryal, Shreyashi, and Balkrishna Kalakheti. "Sex ratio at Birth in a Tertiary Care Hospital in Western Nepal are the Trends Changing?" Journal of Nepal Paediatric Society 36, no. 1 (October 22, 2016): 68–71. http://dx.doi.org/10.3126/jnps.v36i1.15086.

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Introduction: Sex ratio at birth remains unchanged in absence of human intervention. A tendency of skewing towards males is seen in Asian population attributable to various reasons, foremost being abortions. The decreasing number of female population is a form of gender discrimination and has serious implications for both sexes in the future. The purpose of this study was to analyze the trends of sex ratio at birth among deliveries at Lumbini Medical College Teaching Hospital, Palpa, Nepal over the past eight years.Materials and Methods: A retrospective audit of deliveries from 1st January 2008 to 31st December 2015 was carried out. Sex ratio at birth was calculated and its relationship with maternal age, birth order and number of previous abortions was analyzed.Results: The total number of live-births during the study period was 9394 consisting of 5008 male and 4350 female with an overall sex ratio at birth of 112.6. Every year, there was an increasing trend in total number of live births and sex ratio at birth. The number of male births increased with increase in parity but there was no statistical difference seen between maternal age, parity and number of abortions for male and female births.Conclusion: The sex ratio at birth in hospital deliveries is unbalanced with inclination towards male, more so in women with high parity. Additional research exploring the reason for increase in male births is needed, so that potential programs which can reverse this trend can be implemented.J Nepal Paediatr Soc 2016;36(1):68-71
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Veevers, Jean E. "The “Real” Marriage Squeeze." Sociological Perspectives 31, no. 2 (April 1988): 169–89. http://dx.doi.org/10.2307/1389081.

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Among persons in midlife, about one in five is unmarried. The sex ratio in this group is about 80, which is markedly unbalanced. Although changes in fertility and in mortality are contributing factors, the “real” squeeze is due largely to the ubiquitous norm that husbands should be older than their wives. This mating gradient is the most significant determinant of the competition for mates as it is experienced by older unmarried women compared with older unmarried men. The nature and magnitude of this marriage squeeze are demonstrated using Canadian vital statistics and census data. Age differentials of brides and grooms in all marriages registered in 1981 are used to create “availability indices” that estimate the number of unmarried persons of the opposite sex that are potentially available for every 100 unmarried persons. For men, availability indices are low in the 20s, and they increase with advancing age to about one-to-one in the 50s. For women, access to potential grooms is highest in the 20s and decreases with advancing age until, in the 50s, there are only 50 potential grooms per 100 unmarried women. The implications of unbalanced sex ratios are discussed with reference to changes in marriage and the family. Markedly skewed sex ratios may shift the balance of power between the sexes and produce a demographic reaffirmation of the double standard.
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Dissertations / Theses on the topic "Unbalanced sex ratio"

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Stearmer, Steven Matthew. "The Sex Ratio Tipping Point: An Exploration of Crime during Frontier America." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2833.

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Prior research confirms that the number of men in a population is associated with elevated levels of crime. The connection between higher numbers of males relative to females and crime is far less studied in larger aggregate populations, and the nature of the relationship is less clear. This study seeks to answer three questions: are unbalanced sex ratios associated with crime at the state level? At what level does the skew begin to matter? How quickly is the impact observed? These questions are examined through analysis of a novel longitudinal dataset of social characteristics and crime indicators for frontier American states between 1850 and 1920. Fixed effects longitudinal analysis reveals a positive association at the state level between skewed sex ratios - towards both men and women - and crime. This study concludes that any deviation from an equal sex ratio is associated with higher levels in crime, and this impact was demonstrated to occur within a short time frame.
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Scherf, Alexander [Verfasser], and Alexander [Akademischer Betreuer] Schmidt-Catran. "Surplus men : Factors and consequences of unbalanced sex ratios in Germany / Alexander Scherf ; Betreuer: Alexander Schmidt-Catran." Mannheim : Universitätsbibliothek Mannheim, 2020. http://d-nb.info/1203541864/34.

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Books on the topic "Unbalanced sex ratio"

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Shi heng de liang xing "tian ping": Guangdong Sheng chu sheng xing bie bi wen ti tan tao = Lopsided balance in sex : discuss in the unbalance of birth sex ratio in Guangdong province. Beijing Shi: She hui ke xue wen xian chu ban she, 2008.

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Book chapters on the topic "Unbalanced sex ratio"

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Poston, Dudley L., and Li Zhang. "China’s Unbalanced Sex Ratio at Birth: How Many Surplus Boys Have Been Born in China Since the 1980s?" In Gender Policy and HIV in China, 57–69. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-1-4020-9900-7_4.

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Kearney, Robert N., and Barbara Diane Miller. "Unbalanced Sex Ratios." In Internal Migration in Sri Lanka and Its Social Consequences, 39–63. Routledge, 2019. http://dx.doi.org/10.4324/9780429043550-2.

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"Eels at the Edge: Science, Status, and Conservation Concerns." In Eels at the Edge: Science, Status, and Conservation Concerns, edited by Valérie Tremblay. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781888569964.ch6.

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<em>Abstract.—</em>The American eel <em>Anguilla rostrata </em>is declining in the St. Lawrence River watershed, where sex ratio is highly unbalanced in favor of females. Since the American eel is a panmictic species, this demographic dominance is implicated in reproductive potential of the species. The major objective of this study was to evaluate the reproductive strategies of five subpopulations of female eels. It was assumed that fecundity varies among subpopulations according to their migration distance because of the tradeoff between energy allocated to gonads and to somatic tissues. Thirty female silver eels were collected from each of five locations in the St. Lawrence watershed 2,850–4,300 km from the spawning area. Among subpopulations, mean length ranged from 67.9 to 104.3 cm, weight from 595 to 2,366 g, fecundity from 6.5 to 14.5 million oocytes, age from 20 to 23 years, gonadosomatic index from 2.9 to 4.1%, and somatic lipid content from 17.5 to 21.7%. Because of panmixia, no genetic influence on intersite variability is expected. Environmental differences in growth habitats and individual fitness might determine acquisition and allocation of resources, as well as subsequent variability in traits that would affect reproduction. In contrast to previous hypotheses, variations in such traits were attributed to eel size rather than migration distance. The number of oocytes per silver eel was positively correlated with length rather than negatively correlated with migration distance. In the St. Lawrence watershed, large eels are highly fecund regardless of their distance from the spawning ground.
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Ungemah, Joe. "Connection." In Punching the Clock, 16–31. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780190061241.003.0002.

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This chapter brings to life how successful relationships in and outside the workplace are established and maintained. The chapter recounts the development of attachment theory and how our earliest interactions set the stage for all our future relationships. Individuals who benefited from secure relationships are likely to navigate the tenuous nature of the modern workplace more effectively. The chapter also takes a tour of John Gottman’s Love Lab, which has become famous for its ability to break down the ingredients of long-lasting and happy marriages, a finding that has profound implications for professional relationships. When the Magic Ratio of positive to negative interactions becomes unbalanced or if any of the Four Horsemen of criticism, contempt, defensiveness, or stonewalling rear their ugly heads, those in a relationship are forewarned to act quickly and decisively.
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Conference papers on the topic "Unbalanced sex ratio"

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Zhu, Changsheng. "Experimental Study on the Vibration Control Capability of a Hybrid Squeeze Film Damper." In ASME Turbo Expo 2001: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/2001-gt-0252.

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In order to improve the highly nonlinear characteristics of the conventional hydrodynamic squeeze film damper (SFD) in high journal eccentricity ratios and make its dynamic characteristics controllable, a hybrid (combination hydrostatic and hydrodynamic) squeeze film damper (HSFD) is presented. The effectiveness of the hybrid squeeze film damper in attenuating vibration of rotor systems and in improving the high non-linearity of oil film forces of the conventional hydrodynamic SFD is experimentally studied in this paper with a rigid rotor and a flexible rotor. The steady state unbalance responses of rotor-HSFD systems are compared with those of rotor-SFD systems in different radial clearance ratios. It is shown that the HSFD has very good linear dynamic characteristics and can effectively attenuate vibration of rotor systems, especially in larger rotor unbalances and large radial clearance ratios.
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Hai, Pham Minh, and Philip Bonello. "A Computational Parametric Analysis of the Vibration of a Three-Spool Aero-Engine Under Multi-Frequency Unbalance Excitation." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22801.

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The integration of squeeze-film dampers (SFDs) in aero-engine assemblies is a highly cost-effective means of introducing damping in an otherwise lightly damped structure. However, their deployment requires careful unbalance response calculations that take due account of the SFDs’ nonlinearity, particularly when they are unsupported by a centralising spring. Until recently, such calculations were prohibitive due to the large number of assembly modes that typically need to be considered. This problem has been overcome by the authors through the novel Impulsive Receptance Method (IRM) and the Receptance Harmonic Balance Method (RHBM), which efficiently solve the nonlinear problem in the time and frequency domains respectively. These methods have been illustrated on a realistic twin-spool engine and have been shown to be effective for both single frequency unbalance (SFU) excitation (unbalance on a single rotor) and multi-frequency unbalance (MFU) excitation (unbalance on both rotors). In the present paper, the methods are applied to a realistic three-spool engine and the aims are two fold: i) to present some preliminary results of a parametric study into a three-spool aero-engine assembly; ii) to propose a technique that makes use of both IRM and RHBM in producing the speed responses under MFU excitation (from all three rotors), with a realistic speed relation between the rotors. The latter technique is necessary since the speed ratio will vary along a realistic speed characteristic and the authors have previously solved the twin-spool MFU problem under a constant speed ratio condition. The approach used here is to approximate the speed characteristic by one in which the speed ratios are ratios of low integers, enabling the use of RHBM to finish off (to steady state) time-transient solutions obtained through IRM. The parameter study shows that the application of simple bump-spring supports to selected, otherwise unsupported, SFDs, along with slight sealing, should have a beneficial effect on the dynamic response of aero-engines with heavy rotors.
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Fujiwara, Hiroyuki, Hirot Oyama, Norihisa Anegawa, and Osami Matsushita. "Evaluation of Q-Values of a Rotor-Bearing System Using a Modal Open Loop Transfer Function." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50459.

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One of the key features of vibration characteristics (e.g., critical speed, damping ratio, Q-value, instability margin, etc.) of a rotor-bearing system can be described by their eigenvalues. The eigenvalues are conventionally evaluated by feed forward excitations, e.g., hammering test, harmonic sweep excitation, and unbalance response measurement. However it has been difficult to identify their damping ratios under various conditions. In this paper, we introduce a new method using a modal open loop transfer function. This method provides a more accurate Q-value and can help to identify the damping ratio by considering only the mode which we want to measure. We applied this method to a few models and some test rigs: 1) 3DOF model (simulation), 2) A flexible rotor equipped with active magnetic bearings (experiment). As a result, we concluded: 1) As the number of sensors is increased, the accuracy of the measurement also increases. 2) Our new method is more effective in terms of the accuracy of modal damping ratio than the conventional method is.
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Sheu, Geeng Jen. "Dynamics of a Spinning Hollow Rayleigh Beam in General Boundary Conditions." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53402.

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The analytical solutions of the whirl speed, the critical speed and the mode shape of a spinning hollow beam in six general boundary conditions are presented in this paper. The beam is represented by a Rayleigh model with the rotatory moment inertia and the gyroscopic effects. It is shown that the critical speed be written in a function of the whirl ratio (λ) defined by the spinning speed over the whirl speed, the hollowness ratio (α) defined by the hollow area over the total area of the cross section, and the slenderness ratio (l) defined by the beam’s length over its outer radius. Only a finite number of critical speeds exist, and hence finite precessional modes can be found during overall operation ranges when λ &gt; 1/2, and the number is independent of the boundary conditions. The steady state unbalanced response can be therefore expressed analytically in terms of the finite precessional modes in resonance.
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Ma, Yanhong, Jie Hong, Dayi Zhang, and Hong Wang. "Study of Transient Characteristic of a Simple Rigid Rotor Supported on a Squeeze Film Damper With Valvular Metal Rubber Squeeze Film Ring." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27585.

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An efficient oil film damper known as a squeeze film damper with valvular metal rubber squeeze film ring (SFD/VMR) was developed for more effective and reliable vibration control, and especially for improving the blade loss dynamics of high-speed rotors based on the conventional squeeze film damper (SFD). The immobile squeeze film ring of the SFD was replaced by the elastic squeeze film ring with the valvular metal rubber subassembly (VMR) of the SFD/VMR. The squeeze film force properties of the SFD/VMR was improved, because it can passively adjust the squeeze film clearance by taking advantage of the elastic deformation of the VMR and can control the squeeze film clearance in a suitable range. The characteristics of squeeze film stiffness and damping coefficients, as well as the steady-state unbalance response of a simple rigid rotor supported on SFD/VMR and SFD, were reported in a previous literature[1]. In this paper, the transient response of the rigid rotor supported on SFD/VMR and SFD subjected to sudden unbalance of blade loss are inverstigated. Time transient simulation and experimental results indicated that SFD/VMR can operate effectively under much greater unbalance compared with SFD, especially under relative large impact loads of blade loss. The SFD/VMR can suppress the occurrence of the nonlinear vibration phenomenon markedly, such as the bistable jump up phenomenon. Furthermore, the effective eccentricities of SFD/VMR with small transfer ratio (T&lt;1.2) extend to two times of SFD, and optimum film stiffness and damping distribution within the whole film clearance can be achieved.
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Hasan, Nazmul. "Passenger Track Curve Design Criteria: Comfort Criteria, Equivalent Comfort Criteria, and Application." In 2011 Joint Rail Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/jrc2011-56012.

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It is generally recognized by FRA, AREMA, Amtrak, OSHA, and many other applicable authorities that the maximum acceptable rate of radial acceleration for passengers comfort is 0.1g, where ‘g’ is 9.81 m/s/s [1]. Jerk is limited to 0.03g/s [1]. Roll is limited to 1 deg/sec. In this paper all values computed with the aforesaid standard values are referred to as the maximum desirable values as these may be exceeded if needed. Currently there is no procedure in the literature to compute the maximum desirable values. From these comfort criteria the formulae for superelevation run off, rate of change of curvature, radius, and spiral angle etc. are derived. Applications of these formulae and further potential applications thereof are presented. This study is intended for conventional non-tilting train. The equilibrium (Eq), actual (Ea), and unbalance superelevation (Eu) run-off are calculated to be 45 mm/sec, 26 mm/sec and 19 mm/sec respectively. From the run-off rates, the maximum desirable actual and unbalance superlevation comes out to be 87 mm and 63 mm respectively. The desirable ratio between unbalance and actual super-elevation comes to be 0.72. This helps in proportioning equilibrium superelevation to ensure comfort. Equations of spiral length are derived by proportioning 3.33 sec’s ride with the maximum desirable values of superelevation and these equations are found to be exactly the same as those derived another way in the paper no. JRC 2010-36050.
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Yang, S. M., G. J. Sheu, and C. D. Yang. "Analytical Solution of Whirl Speed and Mode Shape for Rotating Shafts." In ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-264.

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The analytical solution of whirl speed and mode shape of a rotating shaft in six boundary conditions is presented in this paper. The shaft is modelled by a Rayleigh beam with rotatory inertia and gyroscopic effects, and the boundary conditions are (1) short-short, (2) long-long, (3) long-free, (4) free-free, (5) long-short, and (6) short-free bearings. It is shown that the whirl speed can be written analytically by a function of the whirl ratio (λ) defined by the rotating speed over the whirl speed and the slenderness ratio (l) defined by the length of the shaft over its radius. The number of whirl speeds, contrary to common belief, is finite when λ > 1/2. For the first time, the rotating system’s unbalanced response can be written analytically in an exact form by a finite number of vibration modes with the corresponding generalized coordinates.
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Gupta, K., and S. Chatterjee. "Dynamics of an Improved Inter Shaft Squeeze Film Damper: Theory and Experiment." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27534.

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Intershaft rolling element bearings are commonly used in aero gas turbine rotors primarily to reduce the length of the engine as well as to avoid obstruction to gas flow path at the turbine end. In order to reduce cross-excitation between the LP and HP shafts of two spool rotor, researchers have proposed introduction of squeeze film in the inter shaft bearing. However, Inter Shaft Squeeze Film Damper (ISSFD) becomes unstable above a threshold operating speeds. In the present work, an improved ISSFD which is inherently stable, is analyzed and tested. It has two rolling element bearings, one each mounted on LP and HP rotor shafts. The two bearings are configured such that the squeeze film is formed between the two non rotating races/surfaces. A centralizing spring between the two races, and a supporting spring between the ground/frame and one of the non rotating races are provided. Two design modifications of this system are analyzed and tested experimentally. Experiments on an improvised two spool rotor setup under unbalance excitation are conducted for all the three designs of ISSFD. In theoretical simulations, various design parameters are varied over a wide range. Theoretical analysis as well as the experiments show that an optimum value of radial clearance exists for a given design to have maximum damping, and a damping ratio of the order of 10% and more is achievable in an ISSFD.
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Murthy, Raghavendra, Marc P. Mignolet, and Aly El-Shafei. "Nonparametric Stochastic Modeling of Uncertainty in Rotordynamics." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59700.

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A systematic and rational approach is presented for the consideration of uncertainty in rotordynamics systems, i.e. in rotor mass and gyroscopic matrices, stiffness matrix, and bearing coefficients. The approach is based on the nonparametric stochastic modeling technique which permits the consideration of both data and modeling uncertainty. The former is induced by a lack of exact knowledge of properties such as density, Young’s modulus, etc. The latter occurs in the generation of the computational model from the physical structure as some of its features are invariably ignored, e.g. small anisotropies, or approximately represented, e.g. detailed meshing of gears. The nonparametric stochastic modeling approach, which is briefly reviewed first, introduces uncertainty in reduced order models through the randomization of their system matrices (e.g. stiffness, mass, and damping matrices of nonrotating structural dynamic systems). Here, this methodology is first extended to permit the consideration of uncertainty in symmetric and asymmetric rotor dynamic systems. Its application is next demonstrated on a symmetric rotor on linear bearings and uncertainties on the rotor stiffness (stiffness matrix) and/or mass properties (mass and gyroscopic matrices) are introduced that maintain the symmetry of the rotor. The effects of these uncertainties on the Campbell diagram, damping ratios, mode shapes, forced unbalance response, and oil whip instability threshold are analyzed. The generalization of these concepts to uncertainty in the bearing coefficients is achieved next. Finally, the consideration of uncertainty in asymmetric rotors is addressed and exemplified.
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Hong, Jie, Meng Chen, and Shuguo Liu. "Application of Whole Engine Finite Element Models in Aero-Engine Rotordynamic Simulation Analysis." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27162.

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The thrust-to-weight ratio of aero-engine is increasing, the structure stiffness is reducing along with its weight, the mechanical exciting force and aerodynamic force become more and more intricate, for these reasons, dynamic interaction of different structures have to be taken into account in aero-engine vibration analysis. In traditional methods, as transfer matrix method and finite element method based on beam element, the rotor is reduced as mass point and beams, so the true dynamic interaction between the disk and shaft can’t be calculated. In this paper, MSC/NASTRAN was developed by adding the effect of gyroscopic moment to the 8 nodes solid element CHEXA with DMAP (direct matrix abstraction program) language. A rotordynamic analysis of a whole engine model based on three-dimensional (3-D) solid element was performed using the program. Firstly, an unbalance response calculation of the casing was performed to predict the translation function (dynamic stiffness) at the bearing support, as well as their effects on rotor dynamics. In the analysis of solid element models and beam element models, the effects of the coupled disks and shafts vibration as well as the corner stiffness between shafts and disks on rotor dynamics were compared, the results shown that various vibration modes could be accurately calculated using the model based on solid element. A phenomenon of the coupled rotor bending and casing vibration was captured, it was shown the third rotor critical speed of the coupled rotor bending and casing vibration mode was a frequency range. The method to predict critical speeds and mode shapes of the rotor considering dynamic interaction between the rotor and casing was investigated. Finally, a simulation platform for aero-engine dynamic analysis was set up, on which the whole engine model could be found and thermal load or aero force could be considered for different purposes. It was concluded that the true dynamic interaction between the rotor and casing as well as the disk and shaft could be captured using the whole engine model based on solid element. Further more, the foreground of the thermal and tip clearance analysis of turbine blades based on the whole engine model was discussed.
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