Search

Many computer systems, such as those for open system environments or multimedia services, need an efficient schedulability test for online admission control of new jobs. Although various polynomial time schedulability tests have been proposed, they often fail to decide the schedulability of the system precisely when the system is heavily loaded. On the other hand, most precise schedulability tests proposed to date have a high complexity and may not be suitable for online tests. In this paper, we present new efficient online schedulability tests for both the periodic process model and the multiframe process model in uniprocessor environments. The schedulability tests are shown to be more precise and efficient than any existing polynomial-time schedulability tests. Moreover, the tests can be done incrementally as each new task arrives at the system. Our proposed tests can also be used for the multiframe model where a task may have different computation times in different periods. We show the performance of the proposed schedulability tests in several simulation experiments. [ABSTRACT FROM AUTHOR]

Replacing power-hungry disks with NAND-flash-based solid-state disks (SSDs) is a recently emerging trend in flash-memory applications. One important SSD design issue is achieving a good balance between cost, performance, and lifetime. This study introduces a hybrid approach to large SSDs that combines MLC NAND flash and SLC NAND flash. Each of these flash architectures has its own drawbacks and benefits, and this study proposes that the two can complement each other. However, there are technical challenges pertaining to data placement, data migration, and wear leveling in heterogeneous NAND flash. The experimental results of our study show that combining 256 MB SLC flash with 20 GB MLC flash produces a hybrid SSD. This hybrid SSD is 1.8 times faster than a purely MLC-flash-based SSD in terms of average response time and improves energy consumption by 46 percent. The proposed hybrid SSD costs only four percent more than a purely MLC-flash-based SSD. The extra cost of a hybrid SSD is very limited and rewarding. [ABSTRACT FROM AUTHOR]

Background: To elucidate clinical experience associated with rare cases of small bowel volvulus among adults, we conducted a retrospective study. Methods: From January 1993 to March 2003 inclusively, we reviewed the presentation and management of 19 patients featuring small bowel volvulus. All study-included patients underwent surgical treatment to confirm their diagnosis. We also analyzed their signs, symptoms, radiological examination details, clinical course and surgical results. Results: The mean age of the study-included 19 patients (13 males, six females) was 61.3 years (range = 16–83 years). All patients suffering from small bowel volvulus were categorized as displaying either primary (no obvious predisposing factors) or secondary volvulus (specific predisposing anatomical abnormalities present). Among them, nine patients were categorized as having primary volvulus, and the remaining 10 were patients with secondary volvulus; this comprised one pregnancy, two malignant stromal tumors of the jejunum, six jejunal diverticula, and one adhesion band. Nine examples of volvulus occurred in the jejunum, four in the ileum, and six in both jejunum and ileum. There were five examples of a counter clockwise rotation of small bowel volvulus. Two patients exhibited bowel wall gangrene, both of whom died subsequent to surgery. The overall mortality rate was 11%. Conclusions: Although small bowel volvulus is rarely seen among adults, when a patient presents with intestinal obstruction, the possibility of small bowel volvulus must be considered. Early surgical intervention should be undertaken in order to prevent vascular compromise. © 2005 Blackwell Publishing Asia Pty Ltd [ABSTRACT FROM AUTHOR]