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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.
31

A New Nonparametric Procedure for the k-sample Problem

Wilcock, Samuel Phillip 18 September 2001 (has links)
The k-sample data setting is one of the most common data settings used today. The null hypothesis that is most generally of interest for these methods is that the k-samples have the same location. Currently there are several procedures available for the individual who has data of this type. The most often used method is commonly called the ANOVA F-test. This test assumes that all of the underlying distributions are normal, with equal variances. Thus the only allowable difference in the distributions is a possible shift, under the alternative hypothesis. Under the null hypothesis, it is assumed that all k distributions are identical, not just equally located. Current nonparametric methods for the k-sample setting require a variety of restrictions on the distribution of the data. The most commonly used method is that due to Kruskal and Wallis (1952). The method, commonly called the Kruskal-Wallis test, does not assume that the data come from normal populations, though they must still be continuous, but maintains the requirement that the populations must be identical under the null, and may differ only by a possible shift under the alternative. In this work a new procedure is developed which is exactly distribution free when the distributions are equivalent and continuous under the null hypothesis, and simulations are used to study the properties of the test when the distributions are continuous and have the same medians under the null. The power of the statistic under alternatives is also studied. The test bears a resemblance to the two sample sign type tests, which will be pointed out as the development is shown. / Ph. D.
32

Secure Quantum Encryption

St-Jules, Michael January 2016 (has links)
To the field of cryptography, quantum mechanics is a game changer. The exploitation of quantum mechanical properties through the manipulation of quantum information, the information encoded in the state of quantum systems, would allow many protocols in use today to be broken as well as lead to the expansion of cryptography to new protocols. In this thesis, quantum encryption, i.e. encryption schemes for quantum data, is defined, along with several definitions of security, broadly divisible into semantic security and ciphertext indistinguishability, which are proven equivalent, in analogy to the foundational result by Goldwasser and Micali. Private- and public-key quantum encryption schemes are also constructed from quantum-secure cryptographic primitives, and their security is proven. Most of the results are in the joint paper Computational Security of Quantum Encryption, to appear in the 9th International Conference on Information Theoretic Security (ICITS2016).
33

Condition Monitoring of MV Remotely Controlled Distributed Disconnectors

Thanopoulos, Sotirios January 2017 (has links)
During the last decades, the power grid is getting rapidly digitalised in order to contribute to theestablishment of Smart Grids and evaluate efficiently the extracted bidirectional data from the powersystem infrastructure. This thesis focuses on the MV grid, since its design and operation have changedmainly because of distributed generation installations and the increased demand of information fromstakeholders. Thus, asset management constitutes a significant tool that can increase the reliability ofthe MV network’s operation and its level of control. Studies have shown that a maintenance planbased on condition monitoring of power system apparatuses would be more effective compared to theimplemented time-based scheduled maintenance.This project focuses on MV remotely controlled disconnectors since studies have shown that theirnumber of failures is double compared to manually operated ones. Since maneuverability andsecondary function are the causes of a major failure with the highest occurrence rate, motor currentmonitoring is studied in this thesis. Some devices that have the capability to monitor disconnectors’motor current, are presented. Additionally, the obtained max motor current measurements areevaluated through a parametric and a non-parametric statistical test. The main challenge of this thesisis to show whether the behaviour of motor current can be an indicator regarding to the disconnector’scondition status.Hence, the impact of different factors on the behaviour of motor current is investigated. It is concludedthat disconnectors without a failure during the studied period are more likely to have max motorcurrent measurements higher than 8A and especially in the interval [10-12]A. The difference in motorcurrent of disconnectors with a work order and without failure is more significant in 2015/2016. Itseems that under the aforementioned values of max motor current, a disconnector is more probable tohave the capability to operate properly. It is also concluded that in case of malfunction “Mellanläge”,the value of max motor current is lower than 8A with higher probability and it maybe indicates aproblem of the studied disconnector.Through the comparison in pairs, it could be concluded that the effect of the external environmentalconditions is not so high on the behaviour of disconnectors’ max motor current measurements. Incontrast, it seems that the implementation of a work order, the number of operations and if adisconnector is installed more northerly in Zone 3 play a more significant role on the behaviour of thisdisconnector’s max motor current measurements. Consequently, based on the aforementioned results itis shown that some of the investigated factors could constitute an indicator whether a disconnector ismore or less probable to have the capability to operate properly.Finally, it is calculated the reduction in the interruption cost that could be achieved in case ofimplementation of motor current monitoring on Vattenfall’s remotely controlled distributeddisconnectors. / Under de senaste årtiondena har kraftnät blivit snabbt digitaliserad För att bidra till upprättandet hosSmart Grids och effektivt utvärdera de extraherade dubbelriktade data från kraftsystemetsinfrastruktur. Denna exjobbsrapport fokuserar på MV-nätet, eftersom dess design och drift harförändrats främst på grund av distribuerade produktionsanläggningar och ökad efterfrågan påinformation från intressenter. Därför utgör ”asset management’’ ett viktigt verktyg som kan öka elnätstillförlitligheten och styrning. Studier har visat att elnäts underhåll baserad på tillståndsövervakningpå kraftsystemkomponenter skulle kunna vara effektivare jämfört med tidsbaserade schemalagdaunderhåll.Detta exjobb fokuserar på MV-fjärrstyrda frånskiljare eftersom studier har visat att deras felfrekvensär dubbelt högre jämfört med manuella. Eftersom problem i manövrerbarhet och sekundär funktionkan orsaka allvarliga fel med hög frekvens, har studien fokuserats på motorströmövervakningen idetta exjobb. Vissa produkter som har förmåga att övervaka frånskiljares motorström, presenteras.Dessutom utvärderas de maximala motorströmsmätningarna genom både parametriskt och ickeparametrisktstatistiskt test. Huvudutmaningen i denna avhandling är att utreda om motors strömmarkan vara en indikator för frånskiljares tillstånd.Olika faktorer hos motorströmmar har också undersökts. Det dras slutsatsen att frånskiljare utanmisslyckande manövern under den studerade perioden är mer benägna att ha maximalamotorströmmar högre än 8A och speciellt i intervallet [10-12] A. Skillnaden i motors strömmar hosfrånskiljare med arbetsorder och utan fel är mer signifikant under åren 2015/2016. Det verkar som attenligt ovan nämnda värden på max motorström, är en frånskiljare mer sannolikt att fungera korrekt.Det kommer också fram till att i händelse av "Mellanläge" är värdet av max motorströmmar lägre än8A med högre sannolikhet, detta kan kanske indikera ett problem hos frånskiljaren.Genom jämförelsen kan man dra slutsatsen att effekten av de yttre miljöförhållandena inte är så högpå maximala motorströmmar hos frånskiljare. Däremot verkar det som om genomförandet av enarbetsorder, antalet operationer och om en frånskiljare är installerad i zon 3 spelar en viktig roll föruppförandet av denna frånskiljares maximala motors strömmen. På grundval av det ovan nämndaresultatet framgår det att några av de undersökta faktorerna kan utgöra en indikator på att om enfrånskiljare är mer eller mindre sannolikt att ha förmågan att fungera korrekt.Slutligen visar beräkningar att minskningen av avbrottskostnaden kan uppnås vid genomförande avmotorströmövervakning på Vattenfalls fjärrstyrda distribuerade frånskiljare.
34

Context-Based Authentication and Lightweight Group Key Establishment Protocol for IoT Devices

Ferrari, Nico January 2019 (has links)
The concept of the Internet of Things is driven by advancements of the Internet with the interconnection of heterogeneous smart objects using different networking and communication technologies. With the rapidly increasing number of interconnected devices present in the life of a person, providing authentication and secure communication between them is considered a key challenge. The integration of Wireless Sensor Networks in the Internet of Things creates new obstacles due to the necessity of finding a balance between the resources utilization and the applied security solutions. In multicast group communications, the energy consumption, bandwidth and processing overhead at the nodes are minimized in comparison to a point-to-point communication system. To securely transmit a message in order to maintain confidentiality of the data and the user’s privacy, usually involves human interaction or the pre-agreement upon some key, the latter unknown to an external attacker. In this thesis, the author proposed an authentication protocol based on the similar context between the correct devices and lightweight computationally secure group-key establishment, avoiding any kind of human involvement. The goal is achieved by having the devices calculate a fingerprint from their ambient context and through a fuzzy commitment scheme generating a commitment respectively opening value which is used to generate a common secret key between them. The tests are effected on real world data accumulated from different environments. The proposed scheme is based on elliptic curve cryptography and cryptographic one-way accumulators. Its feasibility is analyzed by implementing the group key establishment phase in the Contiki operating system and by simulating it with the Cooja simulator. Furthermore, the applicability of the protocol is analyzed and justified by an analysis of the storage overhead, communication overhead, and energy consumption. The simulator shows an energy consumption of only 112 mJ per node for group key establishment. The results obtained in this thesis demonstrate the feasibility of the scheme, it’s computational, and communication costs are further comparable to other similar approaches.
35

以GeoJSON壓縮技術增進網路資料傳輸效能之研究 / Efficiency improvement of spatial data transmission by GeoJSON compression techniques

陳欣瑜, Chen,Hsin Yu Unknown Date (has links)
標準化的地理資料交換格式是開放式地理資訊系統不可或缺的一環,可提供不同的平台經由統一的交換格式而順利進行資料交換。GeoJSON除了具備基本的資料互通性外,其結構簡單且容易讀取的特性為地理資訊服務軟體帶來許多效益。然而座標資料量之多寡直接影響資料傳輸效能,為提昇傳輸效率,必須配合有效的資料壓縮技術以降低傳輸之資料量。此外,GeoJSON壓縮方法的設計與結構訴求,也須融合GeoJSON的概念,以簡單、方便運用與容易了解為目標。 本研究提出一套GeoJSON壓縮技術進行空間資料的壓縮,以降低資料量而增進Web GIS地理資料傳輸的效能。除評估其壓縮效率,並透過不同規模以及不同型態的地理資料,分析影響壓縮效率的原因。最後藉由HTTP壓縮技術輔助,並從資料傳遞的時間與壓縮率,評估本研究提出的方法所帶來的成效。我們同時以單向雜湊函數,建立資料傳遞時的檢查機制,以確保資料傳遞時的正確性與一致性。 實作中,我們採用GeoJSON壓縮技術,進行座標資料的大小減量實驗,結果顯示本研究方法可以得到不錯的壓縮成果與傳輸效能,並且可避免資料傳輸發生問題。 / Standardized GIS data exchanging format is an essential part of Open GIS. This enables GIS data providers, software developers, and system integrators to exchange GIS data from different platform. The simple structure of GeoJSON not only has the data interoperability potential but also has the characteristics of easy processed and readability. These properties directly benefit the GIS service software. However, the amount of spatial information encoded in GIS documents usually has direct impact to the efficiency of GIS data transmission. In order to improve the data transmission efficiency, one has to reduce the amount of spatial data transmitted through data compression techniques. In this thesis, we proposed a data compression mechanism for spatial data. Our mechanism, co-operated with the concept of GeoJSON, aim at simple, easy to understand, and easy to use, can reduce the amount of spatial data transmitted and improve the transmission efficiency. We analyzed the compression ratio of various data types and data amounts through different base parameters. We also measured the system response time reduced using this method and compared with the combination of using our method as well as the HTTP compression modules. A one-way hashing technique is used to ensure data accuracy and consistency during the transmission processes. The experimental results show that our GeoJSON-based compression mechanism can significantly reduce the file size of spatial data and improve the efficiency of spatial data transmission. In addition, the data communication errors can be avoided.
36

Volvo Logistics Corporation Returnable Packaging System : a model for analysing cost savings when switching packaging system

Beselin Hallberg, Jacob, Uhrbom, Per January 2008 (has links)
This thesis is a study for analysing costs affected by packaging in a producing industry. The purpose is to develop a model that will calculate and present possible cost savings for the customer by using Volvo Logistics Corporations, VLC’s, returnable packaging instead of other packaging solutions. The thesis is based on qualitative data gained from both theoretical and empirical studies. The methodology for gaining information has been to study theoretical sources such as course literature and articles, as well as through interviews and consolidation with staff at Volvo Logistics Corporations office in Gothenburg. The model is constructed in Microsoft Excel and consists of six different sheets. The first sheet is a front page that summarises the costs calculated in the other sheets and presents the possible cost savings. After the front page there are three sheets with calculations for the costs in different scenarios, Today’s Situation, VLC Packaging Solution (Pre implementation) and VLC Packaging Solution (Post implementation). The first sheet, Today’s Situation, presents the result of the model that will calculate the customers’ current costs that are associated with packaging. The different costs presented in the model are costs for unloading, repacking, today’s cost for an internal packaging solution, quality related costs, one-way packaging costs and the costs for other packaging solutions. The next sheet, VLC Packaging Solution (Pre), presents an estimation of the cost for thecustomer when using VLC’s returnable packaging system. The estimation will serve as an investment tool, for calculating possible cost savings compared to the present situation. The different costs that will be discussed are handling costs, quality related costs, distribution cost, transaction cost, and investment cost. The third and final calculation sheet, VLC Packaging Solution (Post), presents the actual costs for the customer after the implementation. When the costs have been calculated they will be used to evaluate the actual cost savings for the customer. The last two sheets are a data sheet, which consists of data needed for the calculations in the previous sheets, and an instruction sheet where there are instructions to the different calculations in the model. The conclusion shows that the objective to create a model for calculating the costs for different packaging systems and present possible cost savings is fulfilled.
37

Volvo Logistics Corporation Returnable Packaging System : a model for analysing cost savings when switching packaging system

Beselin Hallberg, Jacob, Uhrbom, Per January 2008 (has links)
<p>This thesis is a study for analysing costs affected by packaging in a producing industry. The purpose is to develop a model that will calculate and present possible cost savings for the customer by using Volvo Logistics Corporations, VLC’s, returnable packaging instead of other packaging solutions.</p><p>The thesis is based on qualitative data gained from both theoretical and empirical studies. The methodology for gaining information has been to study theoretical sources such as course literature and articles, as well as through interviews and consolidation with staff at Volvo Logistics Corporations office in Gothenburg.</p><p>The model is constructed in Microsoft Excel and consists of six different sheets. The first sheet is a front page that summarises the costs calculated in the other sheets and presents the possible cost savings. After the front page there are three sheets with calculations for the costs in different scenarios, Today’s Situation, VLC Packaging Solution (Pre implementation) and VLC Packaging Solution (Post implementation). The first sheet, Today’s Situation, presents the result of the model that will calculate the customers’ current costs that are associated with packaging. The different costs presented in the model are costs for unloading, repacking, today’s cost for an internal packaging solution, quality related costs, one-way packaging costs and the costs for other packaging solutions. The next sheet, VLC Packaging Solution (Pre), presents an estimation of the cost for thecustomer when using VLC’s returnable packaging system. The estimation will serve as an investment tool, for calculating possible cost savings compared to the present situation. The different costs that will be discussed are handling costs, quality related costs, distribution cost, transaction cost, and investment cost. The third and final calculation sheet, VLC Packaging Solution (Post), presents the actual costs for the customer after the implementation. When the costs have been calculated they will be used to evaluate the actual cost savings for the customer. The last two sheets are a data sheet, which consists of data needed for the calculations in the previous sheets, and an instruction sheet where there are instructions to the different calculations in the model.</p><p>The conclusion shows that the objective to create a model for calculating the costs for different packaging systems and present possible cost savings is fulfilled.</p>
38

Long-Term Deflection Of One-Way Concrete Slab Strips Containing Steel And GFRP Reinforcement

Darabi, Mohammadali 14 September 2011 (has links)
Fibre reinforced polymers (FRP’s) are considered an alternative to steel reinforcement in concrete structures because of their noncorrosive nature and nonmagnetic properties. FRP materials are, however, brittle and have a lower stiffness compared to steel. The latter property can lead to deflection and crack control problems in FRP-reinforced concrete flexural members under service loads. A considerable amount of information is available for short-term deflection of FRP-reinforced concrete members, but data on long-term deflections are scarce. This study presents the results of monotonic (short-term) and sustained (long-term) loading tests of 12 concrete shallow beams reinforced with either steel or glass FRP (GFRP) bars. The short-term load-deflection responses of the members are evaluated using existing deflection prediction models (Branson’s and Bischoff’s), and the long-term deflection results (monitored over a period of one year) are used to evaluate the existing ACI code and CSA standard approaches for estimating long-term deflection. The GFRP-reinforced concrete beams exhibited greater amounts of both immediate deflection (under sustained load) and long-term deflections over time, than the steel-reinforced concrete beams. The long-term deflections of both the steel- and GFRP-reinforced concrete beams are overestimated when using the ACI and CSA approaches. Although ACI Committee 440 recommends use of lower values of the long-term deflection multiplier for GFRP-reinforced concrete beams, results obtained from this study suggest that the same longterm multiplier values may be used for GFRP- and steel-reinforced concrete beams loaded at between 115 to 157 days of concrete age.
39

Communication accommodation theory in conversation with second language learners

Rahimian, Mahdi 22 August 2013 (has links)
In this research, Communicative Accommodation Theory (CAT) is investigated while native speakers address nonnative peers. For the intentions of this research, three native speakers of Canadian English were asked to have conversations with native and nonnative peers. The conversations were in the form of giving directions on the map. Later on, the participants’ formants and vowel durations were measured and used for comparing native-nonnative peer effect(s) on the speakers’ vowel formants and duration. Based on the analyses, it is suggested that accommodation may take place based on providing stereotypical vowel durations and formants, as well as reducing inter-token variations in the nonnative peer context.
40

Communication accommodation theory in conversation with second language learners

Rahimian, Mahdi 22 August 2013 (has links)
In this research, Communicative Accommodation Theory (CAT) is investigated while native speakers address nonnative peers. For the intentions of this research, three native speakers of Canadian English were asked to have conversations with native and nonnative peers. The conversations were in the form of giving directions on the map. Later on, the participants’ formants and vowel durations were measured and used for comparing native-nonnative peer effect(s) on the speakers’ vowel formants and duration. Based on the analyses, it is suggested that accommodation may take place based on providing stereotypical vowel durations and formants, as well as reducing inter-token variations in the nonnative peer context.

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