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In recent years, there has been great attention given to skyline queries that incorporate and provide more flexible query operators that return data items (skylines) which are not being dominated by other data items in all dimensions (attributes) of the database. Many variations in skyline techniques have been proposed in the literature. However, most of these techniques determine skylines by assuming that the values of all dimensions for every data item are available (complete). But this assumption is not always true particularly for large multidimensional database as some values may be missing (not applicable during the computation). In this paper, we proposed an efficient approach for processing skyline queries in incomplete database. The experimental results show that our proposed approach has significantly reduced the number of pairwise comparisons and the processing time in determining the skylines compared to the previous approaches.

BackgroundAdolescent smoking problem has still remained as a public health concern, but factors that attributing to the initiation of adolescent smoking are not well known in Iran.ObjectivesThe aim of this study is to estimate the prevalence of smoking, and its associations among high school male adolescents in Iran, in the context of the theory of planned behavior (TPB).Patients and MethodsThis was a cross-sectional study involving male adolescent students (high school) in the city of Zarandieh, Iran. A multiple-stage sampling protocol was used. The participants completed an anonymous, voluntary, and self-report questionnaire. Prevalence was estimated, and demographic variables, psychological factors, and the theory of planned behavior components were used to indicate factors contributing to adolescents’ cigarette smoking.ResultsIn all, 365 students were entered the study. The mean age of respondents was 16.49 ± 1.11 years. The prevalence of current smoking was 15.1%. The result obtained from logistic regression analysis revealed that all theory of planned behavior (TPB) components [knowledge (OR = 0.75; 95% CI: (0.59-0.97), attitude (OR = 0.75; 95% CI: (0.65-0.86), self-efficacy (OR = 0.82; 95% CI: (0.71-0.95), subjective norms (OR = 0.84; 95% CI: (0.72-0.98)] were significant predating factors for adolescents smoking habits. In addition, having parents who smoke (OR = 4.75; 95% CI: (1.38-12.35), smoking friends (OR = 3.76; 95% CI: (1.20-11.76), and smoking siblings (OR = 4.21; 95% CI: (1.17-11.16) were significant contributing factors to adolescents’ cigarette smoking behavior.ConclusionsThe results showed that the prevalence of cigarette smoking in adolescents was high, and the theory of planned behavior (TPB) components were significant predictors of cigarette smoking. It seems that interventions targeting adolescents’ smoking habits might benefit using the TPB model.

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