Differences in the relationship between traumatic experiences, self-esteem, negative cognition, and Internet addiction symptoms among North Korean adolescent defectors and South Korean adolescents: A preliminary study

Park, Subin,Lee, Yeeun,Jun, Jin Yong Elsevier/North Holland Biomedical Press 2017 Psychiatry research Vol.257 No.-

<P><B>Abstract</B></P> <P>North Korean adolescent defectors experience adaptation difficulties along with a wide range of psychosocial problems, but no study has yet examined their Internet addiction symptoms. We compared early traumatic experiences, self-esteem, negative cognition, and Internet addiction symptoms, as well as the relationships between these variables, between North Korean adolescent defectors and South Korean adolescents. Fifty-six North Korean adolescent defectors and 112 age- and sex- matched South Korean adolescents participated. The analyses examined the relationship between traumatic experiences and Internet addiction symptoms, with negative automatic thoughts or low self-esteem as mediators of these relations. North Korean adolescent defectors tended to have higher levels of negative automatic thoughts and more severe Internet addiction symptoms, as well as better self-esteem, than did South Korean adolescents. Furthermore, only among North Korean adolescent defectors, traumatic experiences were positively associated with Internet addition symptoms via increasing negative automatic thoughts. North Korean adolescent defectors are more susceptible to Internet addiction, negative cognitions, and early traumatic experiences compared to South Korean adolescents. However, the cross-sectional design of this study precludes consideration of the causality of these relationships. Interventions aiming to correct negative cognitions and increase self-esteem may be helpful for North Korean adolescent defectors with problematic Internet use.</P> <P><B>Highlights</B></P> <P> <UL> <LI> North Korean adolescent defectors had higher trauma and Internet addiction (IA). </LI> <LI> North Korean defectors also had greater self-esteem and negative automatic thoughts. </LI> <LI> Self-esteem and negative thoughts were mediators in the relation of trauma and IA. </LI> <LI> Country of origin (North vs. South Korea) moderated the mediating effects. </LI> </UL> </P>

Joint hierarchical generalized linear models with multivariate Gaussian random effects

Molas, M.,Noh, M.,Lee, Y.,Lesaffre, E. North-Holland Pub. Co ; Elsevier Science Ltd 2013 Computational statistics & data analysis Vol.68 No.-

Likelihood based inference for correlated data involves the evaluation of a marginal likelihood integrating out random effects. In general this integral does not have a closed form. Moreover, its numerical evaluation might create difficulties especially when the dimension of random effects is high. H-likelihood inference has been proposed where the explicit evaluation of the integral is avoided. The approach also allows extensions handling e.g. (1) complex design experiments, (2) REML type of inference beyond the class of a linear model and (3) overdispersion modeling. The h-likelihood approach to multivariate generalized linear mixed models is extended. The h-likelihood computational algorithms is blended with a Newton-Raphson procedure for the estimation of the correlation parameters. This allows that components of the joint model are interlinked via correlated Gaussian random effects. Further, correlated random effects are allowed within each component. This approach can serve as a basis for further developments of joint double hierarchical generalized linear models with correlated random effects. The methods are illustrated with a rheumatoid arthritis study dataset, where the correlation between latent trajectories of three endpoints is evaluated.

Many-to-many two-disjoint path covers in cylindrical and toroidal grids

Park, J.H.,Ihm, I. North Holland ; Elsevier Science Ltd 2015 Discrete Applied Mathematics Vol.185 No.-

A many-to-many k-disjoint path cover of a graph joining two disjoint vertex sets S and T of equal size k is a set of k vertex-disjoint paths between S and T that altogether cover every vertex of the graph. The many-to-many k-disjoint path cover is classified as paired if each source in S is further required to be paired with a specific sink in T, or unpaired otherwise. In this paper, we first establish a necessary and sufficient condition for a bipartite cylindrical grid to have a paired many-to-many 2-disjoint path cover joining S and T. Based on this characterization, we then prove that, provided the set S@?T contains the equal numbers of vertices from different parts of the bipartition, the bipartite cylindrical grid always has an unpaired many-to-many 2-disjoint path cover. Additionally, we show that such balanced vertex sets also guarantee the existence of a paired many-to-many 2-disjoint path cover for any bipartite toroidal grid even if an arbitrary edge is removed.

M-type smoothing spline estimators for principal functions

Lee, S.,Shin, H.,Billor, N. North-Holland Pub. Co ; Elsevier Science Ltd 2013 Computational statistics & data analysis Vol.66 No.-

We propose a robust method for estimating principal functions based on MM estimation. Specifically, we formulate functional principal component analysis into alternating penalized M-regression with a bounded loss function. The resulting principal functions are given as M-type smoothing spline estimators. Using the properties of a natural cubic spline, we develop a fast computation algorithm even for long and dense functional data. The proposed method is efficient in that the maximal information from whole observed curve is retained since it partly downweighs abnormally observed individual measurements in a single curve rather than removing or downweighing a whole curve. We demonstrate the performance of the proposed method on simulated and real data and compare it with the conventional functional principal component analysis and other robust functional principal component analysis techniques.

Statistical inference and visualization in scale-space using local likelihood

Park, C.,Huh, J. North-Holland Pub. Co ; Elsevier Science Ltd 2013 Computational statistics & data analysis Vol.57 No.-

SiZer (SIgnificant ZERo crossing of the derivatives) is a graphical scale-space visualization tool that allows for exploratory data analysis with statistical inference. Various SiZer tools have been developed in the last decade, but most of them are not appropriate when the response variable takes discrete values. In this paper, we develop a SiZer for finding significant features using a local likelihood approach with local polynomial estimators. This tool improves the existing one (Li and Marron, 2005) by proposing a theoretically justified quantile in a confidence interval using advanced distribution theory. In addition, we investigate the asymptotic properties of the proposed tool. We conduct a numerical study to demonstrate the sample performance of SiZer using Bernoulli and Poisson models using simulated and real examples.

Robust inference using hierarchical likelihood approach for heavy-tailed longitudinal outcomes with missing data: An alternative to inverse probability weighted generalized estimating equations

Lee, D.,Lee, Y.,Paik, M.C.,Kenward, M.G. North-Holland Pub. Co ; Elsevier Science Ltd 2013 Computational statistics & data analysis Vol.59 No.-

We examine methods appropriate for heavy-tailed longitudinal outcomes with possibly missing data. Generalized estimating equations (GEEs) have been widely used in longitudinal studies when data are not heavy-tailed and, in general, are valid only when data are missing completely at random. Robins et al. (1995) showed how inverse probability weighting in such settings (IPW-GEE) can extend validity to data that are missing at random. When data are completely observed, Preisser and Qaqish (1999) proposed the use of robust GEE methods to handle outliers. A natural extension of this to the setting with missing data is to combine these two methods. One alternative for the same setting is to use hierarchical (h-) likelihood (Lee et al., 2006). Here we compare this approach with that of IPW-GEE for heavy-tailed data in the missing data context.

Credibility theory based on trimming

Kim, J.H.T.,Jeon, Y. North-Holland, Pub. Co ; Elsevier Science Ltd 2013 Insurance, mathematics & economics Vol.53 No.1

The classical credibility theory proposed by Buhlmann has been widely used in general insurance applications. In this paper we propose a credibility theory via truncation of the loss data, or the trimmed mean. The proposed framework contains the classical credibility theory as a special case and is based on the idea of varying the trimming threshold level to investigate the sensitivity of the credibility premium. After showing that the trimmed mean is not a coherent risk measure, we investigate some related asymptotic properties of the structural parameters in credibility. Later a numerical illustration shows that the proposed credibility models can successfully capture the tail risk of the underlying loss model, thus providing a better landscape of the overall risk that insurers assume.

Oscillation of harmonic functions for subordinate Brownian motion and its applications

Kim, P.,Lee, Y. North-Holland Pub. Co ; Elsevier Science Ltd 2013 Stochastic processes and their applications Vol.123 No.2

In this paper, we establish an oscillation estimate of nonnegative harmonic functions for a pure-jump subordinate Brownian motion. The infinitesimal generator of such subordinate Brownian motion is an integro-differential operator. As an application, we give a probabilistic proof of the following form of relative Fatou theorem for such subordinate Brownian motion X in a bounded κ-fat open set; if u is a positive harmonic function with respect to X in a bounded κ-fat open set D and h is a positive harmonic function in D vanishing on D<SUP>c</SUP>, then the non-tangential limit of u/h exists almost everywhere with respect to the Martin-representing measure of h.

Potential theory of subordinate Brownian motions with Gaussian components

Kim, P.,Song, R.,Vondracek, Z. North-Holland Pub. Co ; Elsevier Science Ltd 2013 Stochastic processes and their applications Vol.123 No.3

In this paper we study a subordinate Brownian motion with a Gaussian component and a rather general discontinuous part. The assumption on the subordinator is that its Laplace exponent is a complete Bernstein function with a Levy density satisfying a certain growth condition near zero. The main result is a boundary Harnack principle with explicit boundary decay rate for non-negative harmonic functions of the process in C<SUP>1,1</SUP> open sets. As a consequence of the boundary Harnack principle, we establish sharp two-sided estimates on the Green function of the subordinate Brownian motion in any bounded C<SUP>1,1</SUP> open set D and identify the Martin boundary of D with respect to the subordinate Brownian motion with the Euclidean boundary.

On Gorenstein sequences of socle degrees 4 and 5

Ahn, J.,Shin, Y.S. North-Holland Pub. Co 2013 Journal of pure and applied algebra Vol.217 No.5

We determine a new infinite class of symmetric h-vectors that cannot be Gorenstein sequences, a result left open in the works (Boji and Zanello, 2010 [4], Migliore et al. 2008 [17]). This includes the example h=(1,11,10,11,1), which was previously unknown. Combined with known results, this gives a complete characterization of the Gorenstein sequences for codimension @?11 and socle degree 4. These results allow us to prove that every Gorenstein sequence of socle degree 5 and codimension @?15 is unimodal, which improve the interesting results of [4,17] for socle degree 5. Furthermore, our results turn out to be independent of the characteristic of an infinite field k, while the results in [4] hold only when char(k)≠2.