We consider the online scheduling problem of minimizing the total weighted and unweighted completion time on identical parallel machines with preemptible jobs. We show a new general lower bound of 21/19 ≈ 1.105 on the competitive ratio of any deterministic online algorithm for the unweighted problem and 16− √ 14 11 ≈ 1.114 for the weighted problem. We then analyze the performance of the natural...

We study policies aiming to minimize the weighted sum of completion times of jobs in the context of coordination mechanisms for selfish scheduling problems. Our goal is to design local policies that achieve a good price of anarchy in the resulting equilibria for unrelated machine scheduling. In short, we present the first constant-factor-approximate coordination mechanisms for this model. First...

introduction contrast-enhanced fluid-attenuated inversion recovery (flair) is one of the mri sequences that can be used for detection and evaluation of pathological changes in the brain. in this work, we have studied the effect of different echo times (te) on the maximum relationship between signal intensity and concentration of the contrast agent using the flair sequence. materials and methods...

The minimization of makespan in open shop with time lags has been to be shown NP-hard the strong sense even for case two machines and unit-time operations. total completion time, however, remained that though it weighted or jobs release dates. This note shows operations is which answers long standing question.

A natural and basic problem in scheduling theory is to provide good average quality of service to a stream of jobs that arrive over time. In this paper we consider the problem of scheduling n jobs that are released over time in order to minimize the average completion time of the set of jobs. In contrast to the problem of minimizing average completion time when all jobs are available at time 0,...

The novice–expert ratio method (NEM) pinpoints user interface design problems by identifying the steps in a task that have a high ratio of novice to expert completion time. This study tested the construct validity of NEM’s ratio measure against common alternatives. Data were collected from 337 participants who separately performed 10 word-completion tasks on a cellular phone interface. The loga...

We investigate a single machine rescheduling problem that arises from an unexpected machine unavailability, after the given set of jobs has already been scheduled to minimize the total weighted completion time. Such a disruption is represented as an unavailable time interval and is revealed to the production planner before any job is processed; the production planner wishes to reschedule the jo...