Factors Associated With Substance Use Disorders Among Traumatized Homeless Youth

This study aimed to identify homeless youths’ lifestyle and trauma-related risk factors as well as protective factors associated with alcohol use disorder or no disorder and drug use disorder or no disorder. Youth receiving homeless services in Denver (n = 201), Austin (n = 200), and Los Angeles (n = 200; N = 601) completed quantitative interviews assessing demographic information, alcohol and drug use, homeless lifestyle risk factors, trauma-related risk factors, and protective factors. Findings showed differences in trauma-related risk factors between alcohol and drug use disorders, but not homeless lifestyle risks. Protective factors predicted substance use disorders beyond risk factors. Understanding trauma-related risk and protective factors associated with substance use disorders could improve interventions.     

Inference for Time Series Regression Models With Weakly Dependent and Heteroscedastic Errors

Motivated by the need to assess the significance of the trend in some macroeconomic series, this article considers inference of a parameter in parametric trend functions when the errors exhibit certain degrees of nonstationarity with changing unconditional variances. We adopt the recently developed self-normalized approach to avoid the difficulty involved in the estimation of the asymptotic variance of the ordinary least-square estimator. The limiting distribution of the self-normalized quantity is nonpivotal but can be consistently approximated by using the wild bootstrap, which is not consistent in general without studentization. Numerical simulation demonstrates favorable coverage properties of the proposed method in comparison with alternative ones. The U.S. nominal wages series is analyzed to illustrate the finite sample performance. Some technical details are included in the online supplemental material.     

Improving the bandwidth-free inference methods by prewhitening

In this paper we consider inference of parameters in time series regression models. In the traditional inference approach, the heteroskedasticity and autocorrelation consistent (HAC) estimation is often involved to consistently estimate the asymptotic covariance matrix of regression parameter estimator. Since the bandwidth parameter in the HAC estimation is difficult to choose in practice, there has been a recent surge of interest in developing bandwidth-free inference methods. However, existing simulation studies show that these new methods suffer from severe size distortion in the presence of strong temporal dependence for a medium sample size. To remedy the problem, we propose to apply the prewhitening to the inconsistent long-run variance estimator in these methods to reduce the size distortion. The asymptotic distribution of the prewhitened Wald statistic is obtained and the general effectiveness of prewhitening is shown through simulations.     

Changes in characteristics of ego-centred networks of female immigrants married to Korean men

This study explores the relationships between social support and social networks of female immigrants married to South Korean men, using two-year data on migrant wives from the Gyeonggi Welfare Panel and an ego-centred network approach. The results suggest that a larger network with less cohesive ties provides more diverse social support for migrant wives. Migrant wives gradually reduce dependence on their family-in-laws and play roles of support givers for those with the same nationality by sharing their experiences in South Korea. The ego-centred network analysis provides a comprehensive understanding of the social networks of married migrant women in South Korea.     

The binary search decomposition in a decentralized organization

An analytic model of the resource allocation decision process in a decentralized organization is presented. The model follows the philosophy of Kornai and Liptak in its decomposition procedure but employs the binary search technique in its resource allocation process. Briefly, the model provides two important concepts relevant to the decision making process of a decentralized organization: (1) satisficing technique of coordination and (2) simulation of a resource allocation decision process.     

Analysis of Local Acceptance of a Radioactive Waste Disposal Facility

Like many other countries in the world, Korea has struggled to site a facility for radioactive waste for almost 30 years because of the strong opposition from local residents. Finally, in 2005, Gyeongju was established as the first Korean site for a radioactive waste facility. The objectives of this research are to verify Gyeongju citizens' average level of risk perception of a radioactive waste disposal facility as compared to other risks, and to explore the best model for predicting respondents' acceptance level using variables related to cost-benefit, risk perception, and political process. For this purpose, a survey is conducted among Gyeongju residents, the results of which are as follows. First, the local residents' risk perception of an accident in a radioactive waste disposal facility is ranked seventh among a total of 13 risks, which implies that nuclear-related risk is not perceived very highly by Gyeongju residents; however, its characteristics are still somewhat negative. Second, the comparative regression analyses show that the cost-benefit and political process models are more suitable for explaining the respondents' level of acceptance than the risk perception model. This may be the result of the current economic depression in Gyeongju, residents' familiarity with the nuclear industry, or cultural characteristics of risk tolerance.     

Lambda number for the direct product of some family of graphs

An L(2, 1)-labeling for a graph \(G=(V,E)\) is a function f on V such that \(|f(u)-f(v)|\ge 2\) if u and v are adjacent and f(u) and f(v) are distinct if u and v are vertices of distance two. The L(2, 1)-labeling number, or the lambda number \(\lambda (G)\), for G is the minimum span over all L(2, 1)-labelings of G. When \(P_{m}\times C_{n}\) is the direct product of a path \(P_m\) and a cycle \(C_n\), Jha et al. (Discret Appl Math 145:317–325, 2005) computed the lambda number of \(P_{m}\times C_{n}\) for \(n\ge 3\) and \(m=4,5\). They also showed that when \(m\ge 6\) and \(n\ge 7\), \(\lambda (P_{m}\times C_{n})=6\) if and only if n is the multiple of 7 and conjectured that it is 7 if otherwise. They also showed that \(\lambda (C_{7i}\times C_{7j})=6\) for some i, j. In this paper, we show that when \(m\ge 6\) and \(n\ge 3\), \(\lambda (P_m\times C_n)=7\) if and only if n is not a multiple of 7. Consequently the conjecture is proved. Here we also provide the conditions on m and n such that \(\lambda (C_m\times C_n)\le 7\).