We consider the problem of scheduling a set of jobs with different processing times and sizes on a single bounded parallel-batch machine with periodic maintenance. Because the machine is in batch-processing model and the capacity is fixed, several jobs can be processed simultaneously in a batch provided that the total size of the jobs in the batch doesn’t exceed the machine capacity. And the processing time of a batch is the largest processing time of the jobs contained in the batch. Meanwhile, the production of each batch is non-resumable, that is, if a batch cannot be completed processing before some maintenance, that batch needs to be processed anew once the machine returns available. Our goal is to minimize the makespan. We first consider two special cases where the jobs have the same sizes or the same processing times, both of which are strongly NP-hard. We present two different approximation algorithms for them and show that these two algorithms have the same tight worst-case ratio of 2. We then consider the general case where the jobs have the arbitrary processing times and arbitrary sizes, for which we propose a 17/5-approximation algorithm.
To explore the association between bullying and HRQoL among Chinese school-aged children and adolescents utilizing a cross-sectional survey design. Bivariate associations were used to determine the correlation between the experience of bullying and lower HRQoL, and multivariate logistic regressions were evaluated. A total of 2,155 participants, 32.57%, reported experiencing bullying: traditional bullying, 27.80% (n = 599) (β = −3.55, p < .001, SE = 0.41), and cyberbullying, 7.47% (n = 161) (β = −2.50, p < .001, SE = 0.71). The degree of traditional bullying (β = −10.28, p < .001, SE = 1.19) was negatively significantly associated with HRQoL. Other determinants of the impact of the bullying in this cohort were the children's school performance and their relationship with parents, teachers and classmates. 相似文献
VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - While existing literature has conceptualized the multiple, complex ways in which NGOs might relate to the state, it has... 相似文献