Disk performance for random access fares significantly worse compared to sequential access. Time required to transfer random blocks to or from disk is dominated by seeking and rotational delay. To improve the throughput and reduce the latency, one can apply techniques to increase the sequentiality of disk accesses, such as block rearrangement and replication. We introduce an approach to improve read performance by replicating blocks into file system free space at the block level. This makes the replication module independent of the file system and therefore easier to implement and verify. A solution that requires no changes to the file system is also easier to adopt. Supporting a new file system is a matter of writing a user-space component that understands its free block data structures. We implemented a prototype as a stacked device driver for Linux and evaluated its performance on a number of workloads.

BAKGRUND Under sommaren 2013 lyftes en fråga i Europa om det fanns ett behov av en standard för kommersiella diskmaskiner. Svenska aktörer, exempelvis Svensk dagligvaruhandel, kontrollmyndigheter och Sveriges Kommuner och Landsting, svarade ja. Tidigare forskning har tytt på att otillräckligt rena diskmaskiner kan påverka diskresultatet och att smutsiga ytor kan förorena livsmedel och leda till matförgiftning. SYFTE Att studera diskmaskiners renhet och om detta hade något samband med renheten på diskgodset. METOD Tio restauranger i Örebro kommun valdes ut genom ett bekvämlighetsurval. Diskmaskiner kontrollerades med utgångspunkt från en frågeguide och diskgods testades med ATP-mätare. För att analysera resultaten användes pivottabeller i Microsoft Excel och samband signifikanstestades med Chi2-test. RESULTAT Av tio kontrollerade diskmaskiner bedömdes åtta som smutsiga. Drygt hälften av det testade diskgodset fick godkänt, en liten del fick godkänt med anmärkning och cirka en tredjedel fick underkänt. Det diskgods som var smutsigt hade i större utsträckning diskats i smutsiga maskiner. Sambandet mellan olika rengöringsbrister i maskinerna och diskresultat testades, men signifikant samband konstaterades bara mellan förekomst av rödmögel och smutsigt diskgods. Inga tydliga samband sågs med andra variabler kopplade till diskhanteringen. SLUTSATS Diskgods som för ögat ser rent ut är inte alltid det. Det är en fördel om diskmaskinen rengörs ordentligt, men det finns också visst stöd för att rengöring av området runt omkring maskinen, samt hantering, förvaring och slitage har inverkan på diskgodsets renhet. Att diskutera diskhantering vid kontrollbesök kan leda till att ett viktigt område som ibland hamnar i skymundan uppmärksammas. / BACKGROUND A question regarding the need of a standard for commercial dishwashers was raised in Europe during the summer of 2013. Actors in Sweden said yes. Earlier studies has implied that dirty dishwashers could affect the cleanliness of wash ware and that dirty surfaces could contaminate food and lead to food poisoning. OBJECTIVE The aim of this study was to examine the cleanliness of dishwashers and to see if it had some link to the cleanliness of the wash ware. METHOD Food inspections were made at ten restaurants which were selected through a convenience selection.The dishwashers were checked with a study protokol and wash ware were tested with a luminometer. The results were analysed in Microsoft Excel and possible links were tried statistically with Chi2-tests. RESULTS Eight out of ten dishwashers were dirty. A little more than half of the tested wash ware were clean, a few articles were approved with a mark and about a third were dirty. The dirty wash ware were more often washed in a dirty dishwasher. The links between faults in the dishwashers and the ATP-results of the washed goods were tested, but a significant link were only found between red mould and dirty wash ware. For other factors that could affect the cleanliness of the wash ware, no clear links  were to be seen. CONCLUSION Wash ware that seems to be clean aren’t always clean enough. It’s good to keep the dishwasher clean, but there is also some support for that keeping the area around the dishwasher clean, handle and store the wash ware in a appropriate way and to be using wash ware in a good condition impacts the washing-up result. Highlighting the wash routine can lead to more attention to an area that otherwise might tend to be a little bit forgotten.

An understanding of the shape and nature of galaxy density profiles remains a major challenge to galaxy structure studies. The physical mechanisms thought to control these profiles include star formation rates and dynamical interactions, but we focus in this thesis on the contribution of dynamical parameters associated with the dark and baryonic matter. We follow the evolution of mass density profiles, and investigate the development of a truncation radius. Using GADGET-2, an N-body/SPH code with a prescription for star formation and feedback, and the SHARCNET computational facilities, we have generated over 200 galaxy models covering a full range of structural parameters. The galaxy models have a minimum of 1.4 million particles and most are evolved over a period of 10 Gyr. We find that the evolution of the galaxy mass density profile is controlled by the ratio of the disk mass fraction, $m_{d}$, to the halo spin parameter, $\lambda$. The strength of the two-component structure in disk profiles and speed at which this structure develops, is directly proportional to $m_{d}/\lambda$. While the development of a two-component profile is coupled to bar formation, not all barred galaxies develop a two-component profile. We also show that the slope of the outer profile is in close agreement with that of the initial profile and remains stable over time, whereas the inner profile slope evolves considerably. This result will greatly improve comparisons of observed with predicted measures of galaxy density profiles. Our galaxy database is the largest of its kind and a valuable resource for many potential galaxy structural studies. We conclude with a list of future investigations based on our study and new database. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2007-07-30 14:46:24.568

Simulations were performed to determine the effect of turbulence on protoplanets as they accrete inside of a planetary gas disk at the stage of planet formation that involves interactions between relatively large, similar sized bodies. The effect of turbulence was implemented into an existing N-Body code using a parameterization of magnetohydrodynamic (MHD) turbulence performed by Laughlin et. al. (2004). The investigation focussed on the effect of turbulent perturbations on planetary dynamics and accretion at various locations in the disk, particularly at large semimajor axis. At these distances, protoplanet collisions are generally less frequent due to the large induced eccentricities from close encounters and due to the trapping of protoplanets in mutual resonances. It is, however, essential that large protoplanets develop at these distances since some must eventually grow large enough to accrete the massive gas envelopes indicative of the giant planets. The interaction between a protoplanet and the surrounding gas disk creates a torque imbalance acting on the protoplanet, which is generally believed to result in the rapid inward spiraling of the protoplanet. In order to create a fixed region in the disk within which protoplanets may interact without migrating into the central star, two scenarios were considered that would inhibit the inward migration of the protoplanets. The first scenario involved a gas disk that had been truncated at the inner edge, referred to as a planet trap, and the second involved the existence of a stationary giant planet within a gap in the disk, referred to as a planet barrier. Each scenario was tested using different density profiles of the gas disk, different numbers and masses of initial protoplanets, various rates of gas disk decay and also four different levels of turbulence intensities. The results demonstrated that the addition of turbulence to the gas disk promotes planet mixing and results in an increased number of collisions between planets, even at large heliocentric distances. A turbulent disk has the tendency to create a final system where the planets are, on average, larger than those produced in a non-turbulent disk. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2009-09-17 14:41:52.607

Disk performance for random access fares significantly worse compared to sequential access. Time required to transfer random blocks to or from disk is dominated by seeking and rotational delay. To improve the throughput and reduce the latency, one can apply techniques to increase the sequentiality of disk accesses, such as block rearrangement and replication. We introduce an approach to improve read performance by replicating blocks into file system free space at the block level. This makes the replication module independent of the file system and therefore easier to implement and verify. A solution that requires no changes to the file system is also easier to adopt. Supporting a new file system is a matter of writing a user-space component that understands its free block data structures. We implemented a prototype as a stacked device driver for Linux and evaluated its performance on a number of workloads.

Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

The literature on atomization of melts has been reviewed. Models have been developed and applied to analyze the phenomena associated with centrifugal atomization of melts using rotating disk method. Some suggestions and guidelines for the development and operation of a centrifugal atomizer have been given. Previous experiments of melt atomization and present observations of water disintegration at the edge of a rotating disk have confirmed that the disintegration of melts or water occurs in one of three basic modes: direct droplet formation (DDF), ligament formation (LF) and film formation (FF). Wave theories have been used to analyze the disintegration of melts in the different regimes. The equations for the fastest growing wave number have been derived. Models for the calculation of powder particle sizes have been suggested and the calculated results have compared with available experimental data in the literature. Calculations have shown that disk diameter and disk rotating speed are two very important atomizing parameters. The type of melt and melt superheat also affect the powder particles size. In general, fine powder particles can be obtained by increasing disk rotating speed and using large diameter disk, provided that the melt does not solidify on the disk. In the DDF regime waves forming at the periphery of a disk are responsible for the break up of melts. The fastest growing wave number depends on the disk speed, disk diameter and properties of melt. In the FF regime sheet wave theory of Dombrowski and Johns was used to study the collapse of the melt sheet. The fastest growing wave number is a complex function of the speed and thickness of film and the properties of melt and atomizer atmosphere. The effects of disk diameter, disk rotating speed and melt flow rate on atomization are achieved through influencing the speed and thickness of film. The studies on the flow of melts on rotating disks have shown that the film forming on the disk was very thin, about tens of microns and the tangential velocity of melts was much higher than the radial velocity. The analysis of heat transfer of melts on a rotating disk has shown that partial solidification of melts on the disk is possible. To obtain a good atomization condition it is necessary to control the partial freezing of melts on the disk. A large melt superheat and a high melt flow rate are required to prevent melts from freezing on the disk. The use of a small diameter disk can also avoid freezing of the melt on the disk. Combining the calculations of heat transfer on the disk with the prediction of wave theory for particle sizes, it is shown that a disk of small diameter rotating at high speed is desirable for the production of fine powders. The cooling ability obtained by centrifugal atomization using the rotating disk method depends on the design of atomizer, the operating conditions and the type of material to be atomized. A large diameter disk on which solidification of melt is avoided and a high disk rotating speed result to the formation of fine powder particles which experience a high cooling rate. The nucleation undercooling of melt depends on particle size, disk speed, material to be atomized and the nucleation condition. A small particle size and a high disk speed lead to a large undercooling. The times for the completion of solidification of powder particle of typical sizes produced by centrifugal atomization have been calculated and their effects on the atomizer vessel diameter have been discussed.

Disk performance for random access fares significantly worse compared to sequential access. Time required to transfer random blocks to or from disk is dominated by seeking and rotational delay. To improve the throughput and reduce the latency, one can apply techniques to increase the sequentiality of disk accesses, such as block rearrangement and replication. We introduce an approach to improve read performance by replicating blocks into file system free space at the block level. This makes the replication module independent of the file system and therefore easier to implement and verify. A solution that requires no changes to the file system is also easier to adopt. Supporting a new file system is a matter of writing a user-space component that understands its free block data structures. We implemented a prototype as a stacked device driver for Linux and evaluated its performance on a number of workloads. / Science, Faculty of / Computer Science, Department of / Graduate

Disk based model checking does not receive much attention in the model checking field becasue of its costly time overhead. In this thesis, we present a new disk based algorithm that can get close to or faster verification speed than a RAM based algorithm that has enough memory to complete its verification. This algorithm also outperforms Stern and Dill's original disk based algorithm. The algorithm partitions the state space to several files, and swaps files into and out of memory during verification. Compared with the RAM only algorithm, the new algoritm reduces hash table insertion time by reducing the cost and growth of the hash load. Compared with Stern's disk based algorithm, the new disk based algorithm significantly reduces disk vs memory comparsion but increases disk read/write time. The size of the model the new algorithm can verify is bound to the available disk size instead of the available RAM size.

In recent years, thousands of exoplanets have been discovered around a variety of stellar hosts. The disks of gas and dust surrounding young stars are the location and source of material for planet formation. The properties of these protoplanetary disks therefore directly affect the planetary systems that may form. However, the details of the planet formation process are still unclear. In this dissertation, I constrain planet formation mechanisms by measuring the properties of protoplanetary disks, focusing on mass, dust grain growth, and dust settling. I use physically-motivated models and an Artificial Neural Network along with a Markov Chain Monte Carlo (MCMC) fitting procedure to obtain these and other disk properties. This dissertation compiles the largest sample to date of consistently-modeled protoplanetary disks, probing how disk properties vary with host mass and age. The occurrence of planetary companions increases as stellar mass decreases. Thus, brown dwarfs (BDs), with smaller masses than pre-main-sequence stars, may commonly host planets. Studying properties of BD disks and comparing them to pre- main-sequence star disks is therefore important for constraining their planet-forming potential. I present spectral energy distribution (SED) models for BD and pre-main- sequence star disks in four star-forming regions. The SEDs consist of archival photometry data spanning optical to millimeter wavelengths. I model the BD disk SEDs using physically-motivated radiative transfer code; pre-main-sequence star SEDs are modeled using a newly-developed MCMC fitting procedure that allows for a more complete analysis of the disk properties. I compare disk masses and dust settling in these two disk categories to gauge how host mass affects these properties. Typical disk lifetimes are a few tens of millions of years; planet formation likely occurs within the first few million years or less. Comparing how disk properties vary between star-forming regions of different ages can help pinpoint the timeline for planet formation. I present SED models for BDs in four star-forming regions and pre-main-sequence stars in eleven star-forming regions. I obtain the disk masses, dust grain sizes, and amount of dust settling in the disks and discuss the differences and similarities of these properties across regions of varying age.