3,123 research outputs found
Part time employment and happiness: A cross-country analysis
The relationship between part time employment and job satisfaction is analysed for mothers in Germany, Denmark, the Netherlands, Finland, France, Spain and the UK. The impact of working part time on subjective life satisfaction and mental well-being is additionally analysed for British mothers. Cultural traditions concerning women´s role in society, and institutional differences between the countries are exploited. Results indicate that poor quality jobs can diminish any positive well-being repercussions of part time employment. The results additionally suggest that part time mothers in the UK experience higher levels of job satisfaction but not of overall life satisfaction as compared to their full time counterparts
An experimental methodology for a fuzzy set preference model
A flexible fuzzy set preference model first requires approximate methodologies for implementation. Fuzzy sets must be defined for each individual consumer using computer software, requiring a minimum of time and expertise on the part of the consumer. The amount of information needed in defining sets must also be established. The model itself must adapt fully to the subject's choice of attributes (vague or precise), attribute levels, and importance weights. The resulting individual-level model should be fully adapted to each consumer. The methodologies needed to develop this model will be equally useful in a new generation of intelligent systems which interact with ordinary consumers, controlling electronic devices through fuzzy expert systems or making recommendations based on a variety of inputs. The power of personal computers and their acceptance by consumers has yet to be fully utilized to create interactive knowledge systems that fully adapt their function to the user. Understanding individual consumer preferences is critical to the design of new products and the estimation of demand (market share) for existing products, which in turn is an input to management systems concerned with production and distribution. The question of what to make, for whom to make it and how much to make requires an understanding of the customer's preferences and the trade-offs that exist between alternatives. Conjoint analysis is a widely used methodology which de-composes an overall preference for an object into a combination of preferences for its constituent parts (attributes such as taste and price), which are combined using an appropriate combination function. Preferences are often expressed using linguistic terms which cannot be represented in conjoint models. Current models are also not implemented an individual level, making it difficult to reach meaningful conclusions about the cause of an individual's behavior from an aggregate model. The combination of complex aggregate models and vague linguistic preferences has greatly limited the usefulness and predictive validity of existing preference models. A fuzzy set preference model that uses linguistic variables and a fully interactive implementation should be able to simultaneously address these issues and substantially improve the accuracy of demand estimates. The parallel implementation of crisp and fuzzy conjoint models using identical data not only validates the fuzzy set model but also provides an opportunity to assess the impact of fuzzy set definitions and individual attribute choices implemented in the interactive methodology developed in this research. The generalized experimental tools needed for conjoint models can also be applied to many other types of intelligent systems
A fuzzy set preference model for market share analysis
Consumer preference models are widely used in new product design, marketing management, pricing, and market segmentation. The success of new products depends on accurate market share prediction and design decisions based on consumer preferences. The vague linguistic nature of consumer preferences and product attributes, combined with the substantial differences between individuals, creates a formidable challenge to marketing models. The most widely used methodology is conjoint analysis. Conjoint models, as currently implemented, represent linguistic preferences as ratio or interval-scaled numbers, use only numeric product attributes, and require aggregation of individuals for estimation purposes. It is not surprising that these models are costly to implement, are inflexible, and have a predictive validity that is not substantially better than chance. This affects the accuracy of market share estimates. A fuzzy set preference model can easily represent linguistic variables either in consumer preferences or product attributes with minimal measurement requirements (ordinal scales), while still estimating overall preferences suitable for market share prediction. This approach results in flexible individual-level conjoint models which can provide more accurate market share estimates from a smaller number of more meaningful consumer ratings. Fuzzy sets can be incorporated within existing preference model structures, such as a linear combination, using the techniques developed for conjoint analysis and market share estimation. The purpose of this article is to develop and fully test a fuzzy set preference model which can represent linguistic variables in individual-level models implemented in parallel with existing conjoint models. The potential improvements in market share prediction and predictive validity can substantially improve management decisions about what to make (product design), for whom to make it (market segmentation), and how much to make (market share prediction)
Solar total irradiance in cycle 23
The apparently unusual behaviour of the TSI during the most recent minimum of
solar activity has been interpreted as evidence against solar surface magnetism
as the main driver of the secular change in the TSI. We test claims that the
evolution of the solar surface magnetic field does not reproduce the observed
TSI in cycle 23. We use sensitive, 60-minute averaged MDI magnetograms and
quasi-simultaneous continuum images as an input to our SATIRE-S model and
calculate the TSI variation over cycle 23, sampled roughly twice-monthly. The
computed TSI is then compared to the PMOD composite of TSI measurements and to
the data from two individual instruments, SORCE/TIM and UARS/ACRIM II, that
monitored the TSI during the declining phase of cycle 23 and over the previous
minimum in 1996, respectively. Excellent agreement is found between the trends
shown by the model and almost all sets of measurements. The only exception is
the early, i.e. 1996 to 1998, PMOD data. Whereas the agreement between the
model and the PMOD composite over the period 1999-2009 is almost perfect, the
modelled TSI shows a steeper increase between 1996 and 1999 than implied by the
PMOD composite. On the other hand, the steeper trend in the model agrees
remarkably well with the ACRIM II data. A closer look at the VIRGO data, that
make the basis of the PMOD composite after 1996, reveals that only one of the
two VIRGO instruments, the PMO6V, shows the shallower trend present in the
composite, whereas the DIARAD measurements indicate a steeper trend. We
conclude that (1) the sensitivity changes of the PMO6V radiometers within VIRGO
during the first two years have very likely not been correctly evaluated, and
that (2) the TSI variations over cycle 23 and the change in the TSI levels
between the minima in 1996 and 2008 are consistent with the solar surface
magnetism mechanism
The structure of radiative shock waves. III. The model grid for partially ionized hydrogen gas
The grid of the models of radiative shock waves propagating through partially
ionized hydrogen gas with temperature 3000K <= T_1 <= 8000K and density
10^{-12} gm/cm^3 <= \rho_1 <= 10^{-9}gm/cm^3 is computed for shock velocities
20 km/s <= U_1 <= 90 km/s. The fraction of the total energy of the shock wave
irreversibly lost due to radiation flux ranges from 0.3 to 0.8 for 20 km/s <=
U_1 <= 70 km/s. The postshock gas is compressed mostly due to radiative cooling
in the hydrogen recombination zone and final compression ratios are within 1
<\rho_N/\rho_1 \lesssim 10^2, depending mostly on the shock velocity U_1. The
preshock gas temperature affects the shock wave structure due to the
equilibrium ionization of the unperturbed hydrogen gas, since the rates of
postshock relaxation processes are very sensitive to the number density of
hydrogen ions ahead the discontinuous jump. Both the increase of the preshock
gas temperature and the decrease of the preshock gas density lead to lower
postshock compression ratios. The width of the shock wave decreases with
increasing upstream velocity while the postshock gas is still partially ionized
and increases as soon as the hydrogen is fully ionized. All shock wave models
exhibit stronger upstream radiation flux emerging from the preshock outer
boundary in comparison with downstream radiation flux emerging in the opposite
direction from the postshock outer boundary. The difference between these
fluxes depends on the shock velocity and ranges from 1% to 16% for 20 km/s <=
U_1 <= 60 km/s. The monochromatic radiation flux transported in hydrogen lines
significantly exceeds the flux of the background continuum and all shock wave
models demonstrate the hydrogen lines in emission.Comment: 11 pages, 11 figures, LaTeX, to appear in A
Nonthermal hard X-ray excess in the Coma cluster: resolving the discrepancy between the results of different PDS data analyses
The detection of a nonthermal excess in the Coma cluster spectrum by two
BeppoSAX observations analyzed with the XAS package (Fusco-Femiano et al.) has
been disavowed by an analysis (Rossetti & Molendi) performed with a different
software package (SAXDAS) for the extraction of the spectrum. To resolve this
discrepancy we reanalyze the PDS data considering the same software used by
Rossetti & Molendi. A correct selection of the data and the exclusion of
contaminating sources in the background determination show that also the SAXDAS
analysis reports a nonthermal excess with respect to the thermal emission at
about the same confidence level of that obtained with the XAS package
(~4.8sigma). Besides, we report the lack of the systematic errors investigated
by Rossetti & Molendi and Nevalainen et al. taking into account the whole
sample of the PDS observations off the Galactic plane, as already shown in our
data analysis of Abell 2256 (Fusco-Femiano, Landi & Orlandini). All this
eliminates any ambiguity and confirms the presence of a hard tail in the
spectrum of the Coma cluster.Comment: 12 pages, 2 figures. Accepted for publication in ApJ Letter
The Role of Local Policies on Resource Utilization: Timber Harvesting in St. Tammany Parish, Louisiana
Seemingly unrelated regression was used to investigate if the passage of forestry-related ordinances has had an effect upon timber harvesting activities in St. Tammany Parish, Louisiana. Results indicate that a significant negative relationship exists between a $10,000 road bond ordinance and the level of timber harvest in the Parish.Resource /Energy Economics and Policy,
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