DISSECTING PREFERENCE HETEROGENEITY IN CONSUMER STATED CHOICES

This paper investigates alternative methods to account for preference heterogeneity in choice experiments. The main interest lies in assessing the different results obtainable when investigating heterogeneity in various ways. This comparison can be performed on the basis of model performance and, more interesting, by evaluating willingness to pay measures. Preference heterogeneity analysis relates to the methods used to search for it. Socioeconomic variables can be interacted with attributes and/or alternative-specific constants. Similarly one can consider different subsets of data (strata variables) and estimate a multinomial logit model for each of them. Heterogeneity in preferences can be investigated by including it in the systematic component of utility or in the stochastic one. Mixed logit and latent class models are examples of the first approach. The former, in its random variable specification, allows for random taste variations assuming a specific distribution of the attribute coefficients over the population and permit to capture additional heterogeneity by consenting parameters to vary across individuals both randomly and systematically with observable variables. In other words it accounts for heterogeneity in the mean and in the variance of the distribution of the random parameters due to individual characteristics. Latent class models capture heterogeneity by considering a discrete underlying distribution of tastes. The small number of mass points are the unobserved segments or behavioral groups within which preferences are assumed homogeneous. The probability of membership in a latent class can be additionally made a function of individual characteristics. Alternatively, heterogeneity can be incorporated in terms of the random component of utility. The covariance heterogeneity model adopts the second approach representing a generalization of the nested logit model and can be used to explain heteroscedastic error structures in the data. It allows the inclusive value parameter to be a function of choice alternative attributes and/or individual characteristics. An alternative method refers to an extension of the multinomial logit model in which the integration of unobserved heterogeneity is performed through random error components distributed according to a tree. An interesting improvement in modeling preference heterogeneity is related to its simultaneous inclusion in both systematic and stochastic parts. A valid example is the inclusion of an error component part in a random coefficient specification of the mixed multinomial logit model. The empirical data used for comparing the various methods tested relates to departure airport choice in a multi-airport region. The area of study includes two regions in central Italy, Marche and Emilia-Romagna, and four airports: Ancona, Rimini, Forlì and Bologna. A fractional factorial experimental design was adopted to construct a four alternative choice set and five hypothetical choice exercises in each questionnaire. The selection of the potentially most important attributes and their relative levels was developed on the basis of previous research.heterogeneity, airport choice, stated preferences, discrete choice model.

Quality and Public Transport Service Contracts

Public authorities and transport operators are both involved in the provision of public transport services. There is a contrast between the social goals of the former and the private ones of the latter. Regulation plays an important role especially failing competition. Service contracts are the natural method to set bilateral After a brief description of the most important regulatory procedures, we focus our attention on the quality framework in service contracts. In recent years the inclusion of quality requirements in contracts is becoming common practice, especially when adopting price cap regulation. This paper suggests a criterion for service quality definition, measurement and integration in contracts for the production of socially valuable transport services. Using stated preferences methods and choice-based conjoint analysis to analyse customer preferences we estimate the passengers’ evaluation of different service features and calculate a service quality index. A case study demonstrates the procedure to follow for measuring service quality in local public transport.service quality, stated preferences, service contract.

Dynamic response of a damaging masonry wall

A nonlocal damage-plastic model is adopted to describe the nonlinear structural response of masonry structures. The model, based on a macromechanical approach, accounts for strength and stiffness degradation with hysteretic dissipation typically characterizing the masonry response, when it is subjected to horizontal loads. The stiffness recovery due to the crack closure, under cyclic loading, is also introduced by defining two different scalar damage variables for prevailing tensile and compressive states. To explore the effect of such nonlinear phenomena on the masonry structural response, the behavior of an unreinforced slender wall is investigated in the dynamic field. Special attention is devoted to the analysis of the wall frequency response curves (FRCs), obtained by imposing base harmonic accelerations with slowly time-variable frequency. These curves highlight the complexity of the dynamic phenomenon: due to the stiffness decay exhibited by the wall, a continuous variation of its natural frequencies occurs,which in turn modifies the resonance conditions. Finally, the wall response results strongly path-dependent and the characteristics of the wall restoring force lead to multi-valued FRCs

Paying for College: Availability of Need-Based Financial Aid for New Jersey's Working Adults

Examines barriers to low-income working adult students' access to Education Opportunity Fund and Tuition Aid Grants; challenges such as childcare needs; and lack of data for tracking the state's progress in making college affordable. Recommends reforms

A low temperature X-ray single-crystal diffraction and polarised infra-red study of epidote

The effects of low-temperature on the crystal structure of a natural epidote [Ca1.925Fe0.745Al2.265Ti0.004 Si3.037O12(OH), a = 8.8924(7), b = 5.6214(3), c = 10.1547(6) angstrom and beta = 115.396(8)degrees at room conditions, Sp. Gr. P2(1)/m] have been investigated with a series of structure refinements down to 100 K on the basis of X-ray single-crystal diffraction data. The reflection conditions confirm that the space group is maintained within the T-range investigated. Structural refinements at all temperatures show the presence of Fe3+ at the octahedral M(3) site only [%Fe(M3) = 70.6(4)% at 295 K]. Only one independent proton site was located and two possible H-bonds occur, with O(10) as donor and O(4) and O(2) as acceptors. The H-bonding scheme is maintained down to 100 K and is supported by single crystal room-T polarised FTIR data. FTIR Spectra over the region 4,000-2,500 cm(-1) are dominated by the presence of a strongly pleochroic absorption feature which can be assigned to protonation of O(10)-O(4). Previously unobserved splitting of this absorption features is consistent with a NNN influence due to the presence of Al and Fe3+ on the nearby M(3) site. An additional relatively minor absorption feature in FTIR spectra can be tentatively assigned to protonation of O(10)-O(2). Low-T does not affect significantly the tetrahedral and octahedral bond distances and angles, even when distances are corrected for "rigid body motions". A more significant effect is observed for the bond distances of the distorted Ca(1)- and Ca(2)-polyhedra, especially when corrected for "non-correlated motion". The main low-T effect is observed on the vibrational regime of the atomic sites, and in particular for the two Ca-sites. A significant reduction of the magnitude of the thermal displacement ellipsoids, with a variation of U-eq (defined as one-third of the trace of the orthogonalised U-ij tensor) by similar to 40% is observed for the Ca-sites between 295 and 100 K. Within the same T-range, the U-eq of the octahedral and oxygen sites decrease similarly by similar to 35%, whereas those of the tetrahedral cations by similar to 22%

Out-of-plane dynamic response of a tuff masonry wall. Shaking table testing and numerical simulation

The out-of-plane dynamic response of a masonry element is investigated, both experimentally and numerically. The results of shaking table tests on a tuff masonry wall, subjected to harmonic acceleration histories, are presented. An isotropic nonlocal damage-plastic model, accounting for the masonry strength-stiffness degrading and hysteresis mechanisms, is introduced in a finite element procedure to numerically describe the masonry structural response. A simplified scheme is analysed, where the wall is completely restrained at the base and free at the top. The measured top displacement history is compared with that numerically evaluated, obtaining a satisfactory agreement. Moreover, the effects of the onset and evolution of the degrading mechanisms in the masonry wall are highlighted

Self-esteem and mood in obese children and their mothers: A pilot study

Objective: A test-retest pilot study was conducted to examine the relationship between overweight/obesity, self-esteem and mood in a group of school-age children, and the degree to which they changed after a tailored psycho-educational intervention. Before and after administering the psycho-educational training, the following aspects were assessed: the child's weight (BMI); the child's and mother's levels of self-esteem and mood; the mother's perception of their child; and the child's general quality of life. Method: Subject to their prior informed consent, 12 overweight/obese children aged between 8 and 13 years, and their mothers were involved in a psycho-educational intervention, which consisted in four meetings with both the children and their mothers. The study consisted in measuring anthropometric parameters and administering specific psychological tests (the CDI, TMA, BDI, B-SE, and CBCL) to both the children and their mothers before and after the psycho-educational intervention. Results: The results showed that a high BMI was associated with depressive symptoms (anhedonia, negative mood) and low self-esteem (family life, body experience). Low levels of self-esteem were also found in 50% of the mothers, with no correlations between the mother's and child's self-esteem. On analyzing the mothers' clinically significant depressive symptoms (cognitive-affective sphere), it emerged that they included the perception of more problems in their child. After the psycho-educational intervention, there were improvements in: the children's BMI; the children's depressive symptoms and self-esteem; the mothers' depressive symptoms and self-esteem; and the mothers' perceptions of their child's problems. Conclusions: Our case series confirmed the association between overweight/obesity and psychological issues. Overweight/obese children need to be also addressed regarding the psychological fallout of their physical condition. Any intervention must also include the parents, to make them more aware, more committed, and better able to help their child change

Monte Carlo evaluation of the impact of subsequent strokes on backflashover rate

The paper deals with the impact of subsequent strokes on the backflashover rate (BFR) of HV overhead transmission lines (OHLs), assessed by means of an ATP-EMTP Monte Carlo procedure. The application to a typical 150 kV Italian OHL is discussed, simulating several tower grounding system arrangements. Subsequent strokes parameters are added to the statistical simulation variables: Peak current, front time, time-to-half value, lightning polarity, line insulation withstand, lightning location and phase angle of the power frequency voltage. The input data are fed to an ATP-EMTP complete circuit model of the OHL, including line insulation, lightning representation and tower grounding system, the latter simulated by a pi-circuit model able to simulate the effects due to propagation and soil ionization, at modest computational costs. Numerical results evidence a non-negligible BFR increase (in relative terms) due to subsequent strokes: for spatially concentrated grounding systems the BFR increase approximatively vary in inverse proportion with the low frequency grounding resistance, whereas for spatially extended grounding systems the BFR increase depends on the grounding system behavior at high frequencies