Temporal Aggregation of Stationary and Non-stationary Continuous-Time Processes

Abstract.  We study the autocorrelation structure of aggregates from a continuous-time process. The underlying continuous-time process or some of its higher derivative is assumed to be a stationary continuous-time auto-regressive fractionally integrated moving-average (CARFIMA) process with Hurst parameter H . We derive closed-form expressions for the limiting autocorrelation function and the normalized spectral density of the aggregates, as the extent of aggregation increases to infinity. The limiting model of the aggregates, after appropriate number of differencing, is shown to be some functional of the standard fractional Brownian motion with the same Hurst parameter of the continuous-time process from which the aggregates are measured. These results are then used to assess the loss of forecasting efficiency due to aggregation.     

第6章新官上任

《龟航》是一部职场小说, 同时也是一部代表了特定人群的小说,在这个大时代下,境遇变迁,冲击着每一个人。海归的遭遇更能折射出现实的意义。本刊现独家连载这部原创作品。您从作者清新幽默的文笔下读到的将是新世纪《围城》的深刻和感同身受。     

挑战人生

《龟航》是一部职场小说, 同时也是一部代表了特定人群的小说,在这个大时代下,境遇变迁,冲击着每一个人。海归的遭遇更能折射出现实的意义。本刊现独家连载这部原创作品。您从作者清新幽默的文笔下读到的将是新世纪《围城》的深刻和感同身受。     

Venture philanthropy and social entrepreneurship in community redevelopment

This article provides a case study of Tom Cousins, a social entrepreneur who used his own venture philanthropic investments and leveraged additional resources through extensive public‐private partnerships for the sole intent of redeveloping an area of disinvestment and poverty. In the process, Cousins also provided the visionary, strategic, and operational leadership often associated with the actions and responsibilities of a social entrepreneur. The limited research to date has investigated social entrepreneurship and venture philanthropy as separate and often unrelated concepts. In this study, we analyze the sustained and intensive involvement by Cousins and his foundations and the continued leadership provided in the creation of public‐private partnerships focused on the redevelopment of the East Lake area in Atlanta.     

A class of partially linear single‐index survival models

The authors define a class of “partially linear single‐index” survival models that are more flexible than the classical proportional hazards regression models in their treatment of covariates. The latter enter the proposed model either via a parametric linear form or a nonparametric single‐index form. It is then possible to model both linear and functional effects of covariates on the logarithm of the hazard function and if necessary, to reduce the dimensionality of multiple covariates via the single‐index component. The partially linear hazards model and the single‐index hazards model are special cases of the proposed model. The authors develop a likelihood‐based inference to estimate the model components via an iterative algorithm. They establish an asymptotic distribution theory for the proposed estimators, examine their finite‐sample behaviour through simulation, and use a set of real data to illustrate their approach.     

The Timing of Entry Into Fatherhood in Young, At-Risk Men

Timing of first fatherhood was examined in a sample of 206 at-risk, predominantly White men, followed prospectively for 17 years. An event history analysis was used to test a model wherein antisocial behavior, the contextual and familial factors that may contribute to the development of antisocial behavior, and common correlates of such behavior, including academic failure, substance use, and early initiation of sexual behaviors, lead both directly and indirectly to an early transition to fatherhood. Having a mother who was younger at first birth, low family SES, poor academic skills, failure to use condoms, and being in a cohabitating or marital relationship predicted entry into fatherhood. Implications of the findings for prevention of and intervention with early fathering are discussed.     

Poverty Catchments: Migration,Residential Mobility,and Population Turnover in Impoverished Rural Illinois Communities

Abstract Research has thoroughly documented how out‐migration of the educated and skilled from rural areas leaves behind a poorer population and creates pockets of rural poverty. Recently, studies have recognized that the poor are also geographically mobile and that poverty migration patterns can reinforce rural poverty concentrations. In this process, certain impoverished rural communities in economically depressed regions receive a disproportionate share of poverty migrants, concentrating poverty in certain locations. This paper examines the conditions and processes through which poor rural communities become likely destinations for a highly mobile segment of the rural poor and near‐poor. Utilizing case studies of depressed rural Illinois communities, it investigates how the interplay of community factors and the behavior of migrants transforms rural communities from residentially stable to highly mobile, impoverished places.