Linear response for intermittent maps

We consider the one parameter family $\alpha \mapsto T_\alpha$ ($\alpha \in [0,1)$) of Pomeau-Manneville type interval maps $T_\alpha(x)=x(1+2^\alpha x^\alpha)$ for $x \in [0,1/2)$ and $T_\alpha(x)=2x-1$ for $x \in [1/2, 1]$, with the associated absolutely continuous invariant probability measure $\mu_\alpha$. For $\alpha \in (0,1)$, Sarig and Gou\"ezel proved that the system mixes only polynomially with rate $n^{1-1/\alpha}$ (in particular, there is no spectral gap). We show that for any $\psi\in L^q$, the map $\alpha \to \int_0^1 \psi\, d\mu_\alpha$ is differentiable on $[0,1-1/q)$, and we give a (linear response) formula for the value of the derivative. This is the first time that a linear response formula for the SRB measure is obtained in the setting of slowly mixing dynamics. Our argument shows how cone techniques can be used in this context. For $\alpha \ge 1/2$ we need the $n^{-1/\alpha}$ decorrelation obtained by Gou\"ezel under additional conditions.Comment: Minor typos corrected. To appear in Comm. Math. Phy

Development of a Cohesion Questionnaire for Youth: The Youth Sport Environment Questionnaire

The purpose of the current study was to initiate the development of a psychometrically sound measure of cohesion for youth sport groups. A series of projects were undertaken in a four-phase research program. The initial phase was designed to garner an understanding of how youth sport group members perceived the concept of cohesion through focus groups (n = 56), open-ended questionnaires (n = 280), and a literature review. In Phase 2, information from the initial projects was used in the development of 142 potential items and content validity was assessed. In Phase 3, 227 participants completed a revised 87-item questionnaire. Principal components analyses further reduced the number of items to 17 and suggested a two-factor structure (i.e., task and social cohesion dimensions). Finally, support for the factorial validity of the resultant questionnaire was provided through confirmatory factor analyses with an independent sample (n = 352) in Phase 4. The final version of the questionnaire contains 16 items that assess task and social cohesion in addition to 2 negatively worded spurious items. Specific issues related to assessing youth perceptions of cohesion are discussed and future research directions are suggested

Life and reliability of rotating disks

In aerospace applications, an engineer must be especially cognizant of size and weight constraints which affect design decisions. Although designing at or below the material fatigue limit may be desirable in most industrial applications, in aerospace application it is almost mandatory to design certain components for a finite life at an acceptable probability of survival. Zaretsky outlined such a methodology based in part on the work of W. Weibull (1939, 1951) and G. Lundberg and A. Palmgren (1947a, 1947b, 1952). It is the objective of this work to apply the method of Zaretsky (1987) to statistically predict the life of a generic solid disk with and without bolt holes; determine the effect of disk design variables, thermal loads, and speed on relative life; and develop a generalized equation for determining disk life by incorporating only these variables

The Dynamics of Relief Spending and the Private Urban Labor Market During the New Deal

During the New Deal the Roosevelt Administration dramatically expanded relief spending to combat extraordinarily high rates of unemployment. We examine the dynamic relationships between relief spending and local private labor markets using a new panel data set of monthly relief, private employment and private earnings for major U.S. cities in the 1930s. Impulse response functions derived from a panel VAR model that controls for time and city fixed effects show that a work relief shock in period t-1 led to a decline in private employment and a rise in private monthly earnings. The finding offers evidence consistent with contemporary employers' complaints that work relief made it more difficult to hire, even though work relief officials followed their stated policies to avoid affecting private labor markets directly. Meanwhile, negative shocks to private employment led to increases in work relief, consistent with Roosevelt's stated goal of using relief to promote relief and recovery.

Localization of aeroelastic modes in mistuned high-energy turbines

The effects of blade mistuning on the aerodynamic characteristics of a class of bladed-disk assemblies, namely high energy turbines, are discussed. The specific rotor analyzed is the first stage of turbine blades of the oxidizer turbopump in the Space Shuttle Main Engine. The common occurrence of fatigue cracks for these turbine blades indicates the possibility of high dynamic loading. Since mistuning under conditions of weak interblade coupling has been shown to increase blade response amplitudes drastically for simple structural models of blade assemblies, it provides a plausible explanation for the occurrence of cracks. The focus here is on the effects of frequency mistuning on the aeroelastic stability of the assembly and on the aeroelastic mode shapes

A Comparison of Absorption and Emission Line Abundances in the Nearby Damped Lyman-alpha Galaxy SBS 1543+593

We have used the Space Telescope Imaging Spectrograph (STIS) aboard HST to measure a sulfur abundance of [S/H] = -0.41 +/-0.06 in the interstellar medium (ISM) of the nearby damped Lyman-alpha (DLA) absorbing galaxy SBS 1543+593. A direct comparison between this QSO absorption line abundance on the one hand, and abundances measured from HII region emission line diagnostics on the other, yield the same result: the abundance of sulfur in the neutral ISM is in good agreement with that of oxygen measured in an HII region 3 kpc away. Our result contrasts with those of other recent studies which have claimed order-of-magnitude differences between HI (absorption) and HII (emission) region abundances. We also derive a nickel abundance of [Ni/H] < -0.81, some three times less than that of sulfur, and suggest that the depletion is due to dust, although we cannot rule out an over-abundance of alpha-elements as the cause of the lower metallicity. It is possible that our measure of [S/H] is over-estimated if some SII arises in ionized gas; adopting a plausible star formation rate for the galaxy along the line of sight, and a measurement of the CII* 1335.7 absorption line detected from SBS 1543+593, we determine that the metallicity is unlikely to be smaller than we derive by more than 0.25 dex. We estimate that the cooling rate of the cool neutral medium is log [l_c (ergs s^{-1} H atom^{-1})] = -27.0, the same value as that seen in the high redshift DLA population.Comment: 31 pages; accepted for publication in the Ap

Children’s Perceptions of Cohesion

The general purpose of the two studies reported here was to examine perceptions of team cohesiveness in children aged 9 to 12 years. In Study 1, focus groups were used to examine individual perceptions of cohesion from the perspective of group integration—the group as a totality. In Study 2, open-ended questionnaires were used to examine individual perceptions of cohesion from the perspective of individual attractions to the group. The results showed that children as young as nine years understand the phenomenon known as cohesion. They can discuss the group as a totality, the characteristics of cohesive and non-cohesive teams, and identify the major factors attracting them to and maintaining their involvement in the group. Also, the ability to clearly distinguish between task and social cohesion is present. The results provide insight into the world of child sport and emphasise the importance of group cohesion, affiliation, and other social constructs in children’s involvement and adherence to sport groups

An Experimental Investigation of the Differences in Subjective Pilot Workload across Simulated and Real Flight Conditions

An investigation was undertaken to determine the difference in workload between simulated and real flight conditions. The results from the Modified Cooper-Harper and NASA-TLX did not show significance, however, the theoretical implications from the NASA-TLX subscales were of interest. As this is the first study comparing these two environments utilizing subjective workload measures, more research needs to take place in order to provide reliable and valid findings