We study the operation of the segment cleaner in a log structured le system. When the segment cleaner is active, response time for user read requests is adversely aaected. Thus, it is desirable to run the segment cleaner when the read traac is low. We propose a simple strategy for scheduling the segment cleaner that seems to perform an order of magnitude better than a random baseline policy. We...

This paper details the design and implementation of a le system cleaner for a log-structured le system for Linux. This user-level cleaner reclaims disk space which is occupied by blocks no longer referenced by any le in the le system. The current functionality of our cleaner is very limited, but some initial data suggests that performance scales linearly with the amount of data to be cleaned.

We developed and optimized a block-type ultrasonic horn that can be used for cutting hard materials. The proposed sonotrode consists of an aluminum tungsten carbide blade to increase the designed initial block has double slots exponential stepped profile. finite element model analyzed characteristics natural frequency displacement. formulated DOE table response surface perform sensitivity analy...

OBJECTIVE To test an air cleaner and health coach intervention to reduce secondhand smoke exposure compared with air cleaners alone or no air cleaners in reducing particulate matter (PM), air nicotine, and urine cotinine concentrations and increasing symptom-free days in children with asthma residing with a smoker. DESIGN Randomized controlled trial, with randomization embedded in study datab...

Dental healthcare workers (DHCWs) are at high risk of occupational exposure to droplets and aerosol particles emitted from patients' mouths during treatment. We evaluated the effectiveness of an air cleaner in reducing droplet and aerosol contamination by positioning the device in four different locations in an actual dental clinic. We applied computational fluid dynamics (CFD) methods to solve...

This study examined the potential for coal mine roof bolter dust to be a source of a worker’s exposure to respirable quartz. For the models of roof bolter studied, the dust from bolt hole drilling is collected by a dry vacuum exhaust system. The collected dust-laden air passes through a cyclone size-separator (pre-cleaner) and into a collector box containing two additional cyclones and a filter...

Safety of the wheels for high-speed train was investigated when the tread cleaner, which play a role in the increase of adhesion and the removal of dirt, is failed and stuck in wheel tread. The present study was performed on the basis of analyses of a combination of mechanical and thermal load due to the failure of tread cleaner during severe conditions. The finite element method was used to an...

Trade growth for a relatively poor country is thought to shift the composition of industrial output towards dirtier products, aggravating environmental damage. China's rapidly growing trade and serious environmental degradation appear to be no exception. However, much of China's trade growth is attributable to the international fragmentation of production. This kind of trade could be cleaner, i...