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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Proton location in acid center dot center dot center dot pyridine hydrogen bonds of multi-component crystals

Seaton, Colin C. 17 April 2014 (has links)
No / The design of new functional crystalline materials requires an understanding of the factors that control salt and co-crystal formation. These states often only differ in the location of the proton and are influenced by chemical and crystallographic factors. The interaction between a carboxylic acid and a pyridine is a frequently used supramolecular synthon in crystal engineering which can exist as either a co-crystal (CO2H center dot center dot center dot N) or salt (CO2-center dot center dot center dot HN+). The results of a Cambridge Structure Database search indicate that the nature of the functional groups on the pyridine play a stronger role in selection of the phase than those of the acid. However, the nature of the local hydrogen bonding of the interaction also adjusts the potential for proton transfer. This was demonstrated by ab initio modelling of the energy landscape for binary and ternary co-crystals by inclusion of varying components of the local environment.
2

Analys av databasstruktur och stored procedure i syfte att öka prestanda vid hämtning av data

Polprasert, Natthakon, Ahmadi, Mobin January 2019 (has links)
The Company X has a database that continuously increasing which causes the response time when retrieving data from the database increases the more data that is retrieved. Therefore, the company want an analysis of the database structures and stored procedures to see if there is a more efficient way to store and retrieve large datasets. Performance can have different meanings. Within the subject of computer systems, it could be factors such as transaction throughput, response time and storage space. But within the scope of this work performance is limited to the response time. One of the tables in the database is normalized and a few techniques are implemented for stored procedure that the company has not implemented to see if there have been any improvements in performance when retrieving data. The respond time for the various techniques implemented was measured in order to make a comparison on performance. The purpose of this thesis is to analyse database tables and how stored procedure can be improved to find a sustainable solution for the database in the future. Question to the work are: How can the database structure be improved with the aim of increasing performance of data retrieval? Which techniques can improve stored procedure performance when it comes to retrieving large amount of data? The result of this work was that normalization has reduced the respond time for large data retrieval. One of the stored procedure techniques which is called sp_executesql was one of the best techniques which improved the performance of execution time the most when it came to retrieve large amount of data. / Företaget X har en databas som kontinuerligt ökar i storlek vilket detta leder till att svarstiden vid hämtning av data från databasen öka ju mer data som hämtas. Därför vill företaget X att databasstrukturen och stored procedure skulle analyseras för att se om det fanns ett effektivare sätt att lagra samt hämta stora mängder data på. Prestanda kan ha olika betydelser; inom databassystem handlar det om olika faktorer som transaktionsgenomströmning, svarstid och lagringsutrymme. I detta arbete begränsas prestanda till svarstiden. En av tabellerna i databasen normaliseras och sedan implementeras ett antal tekniker för stored procedure som företaget inte har implementerat. Detta för att kunna se om det har skett förbättringar i prestanda vid hämtning av data. Därefter mätes svarstiden för de olika teknikerna som implementerades för att kunna göra en jämförelse på prestanda. Syftet med arbetet är att analysera databastabeller samt analysera hur stored procedure kan förbättras för att hitta en hållbar lösning för databasen i framtiden. Frågeställningar till arbetet är: Hur kan databasstrukturen förbättras i syfte att öka prestanda vid hämtning av data? Samt vilka tekniker kan förbättra prestanda för stored procedure vid hämtning av stora datamängder? Resultatet av arbetet blev att med hjälp av normalisering har svarstiden minskat för hämtning av stora datamängder samt att sp_executesql är den teknik inom stored procedure som är överlägset bäst av de tekniker som har implementerats när det gäller prestanda vid hämtning av stora datamängder.
3

Implementation and evaluation of data persistence tools for temporal versioned data models / Implementation och utvärdering av persistensverktyg för temporala versionshanterade datamodeller

Knutsson, Tor January 2009 (has links)
<p>The purpose of this thesis was to investigate different concepts and tools which could support the development of a middleware which persists a temporal and versioned relational data model in an enterprise environment. Further requirements for the target application was that changes to the data model had to be facilitated, so that a small change to the model would not result in changes in several files and application layers. Other requirements include permissioning and audit tracing. In the thesis the reader is presented with a comparison of a set of tools for enterprise development and object/relational mapping. One of the tools, a code generator, is chosen as a good candidate to match the requirements of the project. An implementation is presented, where the chosen tool is used. An XML-based language which is used to define a data model and to provide input data for the tool is presented. Other concepts concerning the implementation is then described in detail. Finally, the author discusses alternative solutions and future improvements.</p>
4

Implementation and evaluation of data persistence tools for temporal versioned data models / Implementation och utvärdering av persistensverktyg för temporala versionshanterade datamodeller

Knutsson, Tor January 2009 (has links)
The purpose of this thesis was to investigate different concepts and tools which could support the development of a middleware which persists a temporal and versioned relational data model in an enterprise environment. Further requirements for the target application was that changes to the data model had to be facilitated, so that a small change to the model would not result in changes in several files and application layers. Other requirements include permissioning and audit tracing. In the thesis the reader is presented with a comparison of a set of tools for enterprise development and object/relational mapping. One of the tools, a code generator, is chosen as a good candidate to match the requirements of the project. An implementation is presented, where the chosen tool is used. An XML-based language which is used to define a data model and to provide input data for the tool is presented. Other concepts concerning the implementation is then described in detail. Finally, the author discusses alternative solutions and future improvements.

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