Flutter and forced response of mistuned rotors using standing wave analysis

A standing wave approach is applied to the analysis of the flutter and forced response of tuned and mistuned rotors. The traditional traveling wave cascade airforces are recast into standing wave arbitrary motion form using Pade approximants, and the resulting equations of motion are written in the matrix form. Applications for vibration modes, flutter, and forced response are discussed. It is noted that the standing wave methods may prove to be more versatile for dealing with certain applications, such as coupling flutter with forced response and dynamic shaft problems, transient impulses on the rotor, low-order engine excitation, bearing motion, and mistuning effects in rotors

Apple orchard frost protection with wind machine operation

Research has shown that wind machines are more effective under conditions of strong thermal inversions. Quantitative relationships between the level of protection and inversion strength, however, are not well known, and there are few reports on the effect of fan operation on energy balance. Whether the wind machines should be started before surface cooling causes turbulence damping and atmospheric stratification or if it is possible to delay starting until just before the critical temperature occurs remains a matter of discussion. Therefore, experiments were conducted on 11 spring frost nights during the 1999 and 2000 to assess the effectiveness of a fan operation on frost protection of an apple orchard under different microclimatic conditions. The 11 frost events were characterized by light winds (0.58–1.92 m s−1) and clear skies for most of the night, resulting in an average accumulated radiative loss of 2.67 ± 0.38 MJ m−2. The air temperature increased immediately after the wind machines were started and the temperature rise depended on inversion strength. For each 1 °C increase in temperature inversion strength between 1.5 and 15 m height, wind machine operation caused a 0.3 °C increase of air temperature at a 1.5 m height within the main area affected by the fan operation. Using multiple regression, the area protected was significantly related to the temperature increase and the inversion strength. Wind machine operation reduced flower damage by 60% in 1999 and 37% in 2000. Distribution of flower damage varied spatially, and it was related to wind drift

Modelling apple flower and fruit damage to frost

Good quality apples are grown in relatively cold areas. However, frost frequently causes damage to flowers and small fruits. When the percentage of frost damage losses is higher than the thinning requirement of the cultivar, production is reduced. In addition to reducing yield, frost damage to the skin and malformation of the fruits often devalues the quality and reduces profits. Critical temperature tables in relation to phenological stage are available for apples and other deciduous crops (Ballard and Proebsting, 1978; Proebsting and Mills, 1978). Some of the data came from field observations using temperatures from standard shelters and some came from excised branch chamber studies. Since plants adapt to the short term temperature environment and there are biological and physical phenomena that influence the critical damage temperature, extrapolation of these critical temperatures to a given crop and environment is questionable. For a thorough discussion see Snyder et al. (2004). In this paper, a program that predicts the fraction of damage to flowers and fruits, and hence the reduction of high quality production, is presented and validated using minimum temperature data and the observed fraction of damaged apple flowers of three cultivars from 13 locations over two years of multiple frost events

A Simple Colorimetric Method for the Estimation of Relative Numbers of Lactobacilli in the Saliva

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67295/2/10.1177_00220345400190040101.pd

ELM triggering conditions for the integrated modeling of H-mode plasmas

Recent advances in the integrated modeling of ELMy H-mode plasmas are presented. A model for the H-mode pedestal and for the triggering of ELMs predicts the height, width, and shape of the H-mode pedestal and the frequency and width of ELMs. Formation of the pedestal and the L-H transition is the direct result of ExB flow shear suppression of anomalous transport. The periodic ELM crashes are triggered by either the ballooning or peeling MHD instabilities. The BALOO, DCON, and ELITE ideal MHD stability codes are used to derive a new parametric expression for the peeling-ballooning threshold. The new dependence for the peeling-ballooning threshold is implemented in the ASTRA transport code. Results of integrated modeling of DIII-D like discharges are presented and compared with experimental observations. The results from the ideal MHD stability codes are compared with results from the resistive MHD stability code NIMROD.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

A wider Europe? The view from Russia, Belarus and Ukraine

On the evidence of national surveys conducted between 2000 and 2006, there is a declining sense of European self-identity in the three Slavic post-Soviet republics of Russia, Belarus and Ukraine. Attitudes towards the European Union and the possibility of membership are broadly supportive, but with a substantial proportion who find it difficult to express a view, and substantial proportions are poorly informed in comparison with the general public in EU member or prospective member countries. Those who are better informed are more likely to favour EU membership and vice versa. Generally, socioeconomic characteristics (except for age and region) are relatively poor predictors of support for EU membership as compared with attitudinal variables. But ‘Europeanness’ should not be seen as a given, and much will depend on whether EU member countries emphasize what is common to east and west or establish ‘new dividing lines’ in place of those of the cold war

Random Convex Hulls and Extreme Value Statistics

In this paper we study the statistical properties of convex hulls of $N$ random points in a plane chosen according to a given distribution. The points may be chosen independently or they may be correlated. After a non-exhaustive survey of the somewhat sporadic literature and diverse methods used in the random convex hull problem, we present a unifying approach, based on the notion of support function of a closed curve and the associated Cauchy's formulae, that allows us to compute exactly the mean perimeter and the mean area enclosed by the convex polygon both in case of independent as well as correlated points. Our method demonstrates a beautiful link between the random convex hull problem and the subject of extreme value statistics. As an example of correlated points, we study here in detail the case when the points represent the vertices of $n$ independent random walks. In the continuum time limit this reduces to $n$ independent planar Brownian trajectories for which we compute exactly, for all $n$, the mean perimeter and the mean area of their global convex hull. Our results have relevant applications in ecology in estimating the home range of a herd of animals. Some of these results were announced recently in a short communication [Phys. Rev. Lett. {\bf 103}, 140602 (2009)].Comment: 61 pages (pedagogical review); invited contribution to the special issue of J. Stat. Phys. celebrating the 50 years of Yeshiba/Rutgers meeting

Sex Segregation and Salary Structure in Academia

This article reports a study of aggregate unit salary levels, within a major research university. We analyze these salary levels, as they are influenced by unit sex composition, and modified by unit attainment levels—where unit refers to the departments, colleges and schools, and other academic divisions of the university. We investigate three central issues of sex and salary, previously overlooked in salary studies of academic employees: Do high proportions of women depress men's unit salary levels ("competition" hypothesis)? Are women's salary levels higher in male-dominated, and lower in female-dominated, units ("concentration" hypothesis)? Are men salary-compensated for working with women ("compensation" hypothesis)? The findings support none of these hypotheses. Rather, the relationship between unit sex composition and salary rests upon the connection between units' composition and attainment levels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69126/2/10.1177_073088848100800103.pd