The technical characteristics of electricity generation and transmission have implications for the way in which economic principles are adapted to evaluate pricing and regulation issues in electricity markets. In particular, there is an externality associated with the way in which electricity flows in networks because of Kirchoff's laws. In this paper, a mathematical programming model is presented that simulates a competitive electricity market, based on the spatial-intertemporal equilibrium models pioneered by Takayama and Judge (1971). The model is used to simulate the operation of a hypothetical electricity market, illustrating some of the issues arising from the network externality. 相似文献
This paper uses a new source of data to study the dramatic increase in cohabiting unions in Great Britain. It analyses, in turn, entry into first partnership, the stability of cohabiting unions and repartnering after dissolution of cohabitation. In excess of 70% of first partnerships are now cohabitations, and these last a relatively short time before being either turned into marriage or dissolved. The shift to cohabitation as the dominant mode of first partnership plays an important role in the delay of first marriage and motherhood. The paper also investigates the factors that are associated with the outcome of cohabitations. 相似文献
In sequential studies, formal interim analyses are usually restricted to a consideration of a single null hypothesis concerning a single parameter of interest. Valid frequentist methods of hypothesis testing and of point and interval estimation for the primary parameter have already been devised for use at the end of such a study. However, the completed data set may warrant a more detailed analysis, involving the estimation of parameters corresponding to effects that were not used to determine when to stop, and yet correlated with those that were. This paper describes methods for setting confidence intervals for secondary parameters in a way which provides the correct coverage probability in repeated frequentist realizations of the sequential design used. The method assumes that information accumulates on the primary and secondary parameters at proportional rates. This requirement will be valid in many potential applications, but only in limited situations in survival analysis. 相似文献
Developmental theories depend on characterizing the input to potential learning mechanisms—infants’ everyday experiences. The current study employed a novel ecological momentary assessment (EMA) to measure two aspects of the physical context of those experiences: body position and location. Infant body position was selected because it relates to the development of a variety of other skills. Caregivers of 3‐, 6‐, 9‐, and 12‐month‐olds reported infants’ body position—held, supine, reclined, prone, sitting, or upright—in response to text message notifications over a week to capture infants’ experiences across the entire range of their daily activities. Findings revealed a tremendous disparity in the distribution of body position experiences over the first year. Younger infants spend more time held, supine, and reclined, whereas older infants spend more time sitting and upright. Body position experiences differed substantially between same‐age infants who possess a motor skill (e.g., ability to sit or walk) compared with those who did not, suggesting that developing motor skills change infants’ everyday experiences. Finally, the success of the methodology suggests that similar EMAs might be used to study a wide range of infants’ naturalistic experiences. 相似文献
There have been few studies investigating the relationship between the built environment and the status of bird distributions in small island tropical urban areas. We present a study investigating the relationship between bird species richness, abundance and assemblage to the built environment in Suva, Fiji. Field surveys were taken at 54 randomly selected sites throughout the city, stratified by three building density classes and the central business district (CBD). At each site bird counts were recorded, along with environmental data such as average building height, within a 150 m radius. Land-use information was obtained from screen digitized high-resolution satellite imagery within the same radius. Distance to undeveloped patches of land within the urban area was calculated using a GIS. Analysis of the effects of the built environment was carried out for all species, and for exotic and native species separately. Abundance of exotics was significantly higher in the central business district (CBD) than all other urban density classes, and significantly higher than natives in all other density classes. We found a negative relationship between native species richness and distance to undeveloped patches, but no relationship for exotics. Species assemblage was not related to urban density class. We conclude that the status of native and exotic bird species in Suva is similar to what has been found in urban areas in temperate climates, and conservation efforts should focus on minimizing the amount of heavily urbanized “core areas” and protecting undeveloped areas of forested vegetation to improve bird biodiversity in small tropical islands cities.
In this paper I argue that something important, and something social, is missing from contemporary accounts of social cognition, social neuroscience and evolutionary social psychology. Contemporary accounts of social cognition focus on cognition directed towards social objects, that is, towards persons and social groups. In contrast, early twentieth century accounts of socially engaged cognition focused upon beliefs and attitudes oriented to the represented beliefs and attitudes of members of social ‘reference groups’ and directed towards both social and non‐social objects. I argue that this earlier conception of socially engaged cognition should be integrated with contemporary research on social cognition, social neuroscience and evolutionary social psychology, since it poses a challenge but also an opportunity for these disciplines. 相似文献
Researchers have theorized about the role of sexual shame as a mechanism through which sexual minority stress manifests into mental health difficulties, such as sexual compulsivity for gay and bisexual men (GBM), and about the resilience-promoting effects of sexual pride. However, no validated measures to date have directly tapped into these constructs rather than using proxies for them, such as internalized homonegativity. We developed the Sexual Shame and Pride Scale (SSPS) and conducted a psychometric evaluation of it using a sample of 260 highly sexually active GBM. The scale had the expected structure in factor analysis and showed evidence of internal consistency and test–retest reliability. Correlational analyses demonstrated the convergent validity of sexual shame and sexual pride with relevant constructs. Regression analyses demonstrated the predictive validity of sexual shame in relation to sexual compulsivity, accounting for unique variability even after adjusting for previously demonstrated etiological factors, and the predictive validity of both shame and pride, which interacted to consistently predict four sexual behavior outcomes. Findings suggest the SSPS is a psychometrically valid and reliable measure that may be useful in future empirical work and highlight preliminary evidence for the role of these constructs in the sexual health of GBM.相似文献
This article describes an unconventional participatory development approach carried out in an informal e‐waste hub in South‐West Hebron, an area that has collected and processed the bulk of Israeli e‐waste for over a decade. Our approach contributes to the critique and recovery of community representation in participatory development and the search for ways to facilitate representative community engagement. Specifically, we describe our use of a novel Delphi‐like method that allowed us to facilitate a broadly endorsed development trajectory within a heterogeneous and conflicted community. We show how the results yielded by this approach diverged from those that were likely to emerge from more facile forms of participation in ways that are important for other similar e‐waste hubs internationally, which face a destructive status quo on the one hand, or the economically ruinous international policies that ban e‐waste trade from “developed” to “developing” countries on the other. Despite real tensions and cleavages within the affected communities, the process described facilitated a shift from deadlocked environmental versus livelihood positions towards building capacity and regulating existing informal e‐waste trades to preserve livelihoods dependent on these. 相似文献