9,602 research outputs found
High-sensitivity tool for studying phonon related mechanical losses in low loss materials
Fundamental mechanical loss mechanisms exist even in very pure materials, for
instance, due to the interactions of excited acoustic waves with thermal
phonons. A reduction of these losses in a certain frequency range is desired in
high precision instruments like gravitational wave detectors. Systematic
analyses of the mechanical losses in those low loss materials are essential for
this aim, performed in a highly sensitive experimental set-up. Our novel method
of mechanical spectroscopy, cryogenic resonant acoustic spectroscopy of bulk
materials (CRA spectroscopy), is well suited to systematically determine losses
at the resonant frequencies of the samples of less than 10^(-9) in the wide
temperature range from 5 to 300 K. A high precision set-up in a specially built
cryostat allows contactless excitation and readout of the oscillations of the
sample. The experimental set-up and measuring procedure are described.
Limitations to our experiment due to external loss mechanisms are analysed. The
influence of the suspension system as well as the sample preparation is
explained.Comment: 4 pages, 3 figures, proceedings of PHONONS07, submitted to Journal of
Physics: Conference Serie
Conservative-dissipative approximation schemes for a generalized Kramers equation
We propose three new discrete variational schemes that capture the
conservative-dissipative structure of a generalized Kramers equation. The first
two schemes are single-step minimization schemes while the third one combines a
streaming and a minimization step. The cost functionals in the schemes are
inspired by the rate functional in the Freidlin-Wentzell theory of large
deviations for the underlying stochastic system. We prove that all three
schemes converge to the solution of the generalized Kramers equation
Twice Chosen: Spouse Matching and Earnings Among Women in First and Second Marriages
This study examines spousal matching for females in second-order marriages. It is based on detailed data from longitudinal Swedish population data registers. We aim to follow women who marry, divorce, and subsequently remarry compared with females who marry and stay married over the course of the study interval. The earnings of both groups are modeled through regression analysis in the year prior to their marriages along with the earnings of each husband. The residuals from the regressions represent unobservables in the process of earnings generation. From the regressions we obtain spouse-to-be pairs of earnings residuals and we measure the correlation of residuals for each marital regime. Overall, we find significant positive correlations for all three of the marital partitions. The correlation tends to be smaller for the first of a sequence of marriages for women who divorce than for women who marry and stay so. For the second of the successive marriages, however, the correlation of the residuals is larger than that for women who marry but once. We also find evidence of “matching” between successive husbands. Women who marry men with unmeasured positive earnings capacities, in the event of divorce, tend to select and match in a similar fashion the second time around.Marital matching; Remarriage; Assortative mating; Earnings
Spin Glass and antiferromagnetism in Kondo lattice disordered systems
The competition between spin glass (SG), antiferromagnetism (AF) and Kondo
effect is studied here in a model which consists of two Kondo sublattices with
a gaussian random interaction between spins in differents sublattices with an
antiferromagnetic mean Jo and standard deviation J. In the present approach
there is no hopping of the conduction electrons between the sublattices and
only spins in different sublattices can interact. The problem is formulated in
the path integral formalism where the spin operators are expressed as bilinear
combinations of Grassmann fields which can be solved at mean field level within
the static approximation and the replica symmetry ansatz. The obtained phase
diagram shows the sequence of phases SG, AF and Kondo state for increasing
Kondo coupling. This sequence agrees qualitatively with experimental data of
the Ce_{2} Au_{1-x} Co_{x} Si_{3} compound.Comment: 7 pages, 1 figure, submitted to EPJ
For To All Those Who Have, More Will be Given: The Matthew Effect, Nonprofit Organizations, and the Adoption of Internet Technology
This study assesses the adoption of Internet-based communication by nonprofit organizations. The research literature posits that the Internet may serve as a ‘leveler’ between rich and poor organizations by lowering the transaction costs of communication, by lowering costs of access to information and by reducing the scale-economy advantages that larger and well-resourced organizations usually enjoy. This literature contrasts with Robert Merton’s Matthew Effect, in which the better-resourced advance and the lesser resourced do not (Merton and Zuckerman 1973(1968)). This study attempts to determine what characteristics distinguish the nonprofit organizations that adopt Internet technologies. This study uses a multi-method approach to ascertain these structural and financial characteristics (Campbell and Fiske 1959; Brewer and Hunter 1989; Judd, Smith et al. 1991). The data collected during this research include case studies of Roman Catholic higher education institutions, content analysis of institutional WWW sites, and a large-scale national survey of randomly chosen nonprofit organizations as a baseline data set on adoption and usage of the Internet among v nonprofit organizations. Results of these analyses suggest that while earlier patterns of adoption perdure in some nonprofit organizations and other organizations have Internet connectivity, as of the year 2000—some six years after the general availability of WWWbased technologies—the adoption of some of these technologies has already occurred, calling into question the Matthew Effect and comparable concerns about a “Digital Divide.” Nearly 90 percent of nonprofit organizations use electronic mail and have access to the Internet as of July 2000. However, only two-thirds of nonprofit organizations have WWW sites and only 20 percent of organizations use their respective WWW sites for electronic fundraising. Regression analysis suggests a positive correlation between the use of Internet technologies and the variables: organization size, assets, information technology (IT) investment, IT personnel, and history of innovation adoption. The same analysis finds a negative correlation between Internet usage and available financial resources
Regulatory Effectiveness in The Electric Utility Industry: An Empirical Analysis
An established result in the theory of the regulated firm is that an effective rate-of-return constraint induces the firm to employ larger proportions of capital inputs to noncapital inputs than would be the case in the absence of the regulatory constraint. This overcapitalization, often referred to as the Averch-Johnson effect, has been the subject of several recent empirical studies of the electric utility industry. The present study adds to this body of literature. It seeks to test for the effectiveness of utility regulation in the context of a cost minimization model which includes the allowed rate of return as an explanatory variable and permits arbitrary elasticities of substitution for any pair of inputs
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