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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.
91

Simulating Chemical Reactions of Glass Powder in Cement Using Silica, Calcium Hydroxide and Sodium Hydroxide

Young, Sarah 04 1900 (has links)
<p>The use of supplementary cementitious materials (SCM) decreases the environmental impact of the cement industry. SCMs are commercial by-products that possess pozzolanic properties. Recycled glass powder, classified as a SCM, when added as a cement replacement reacts with the available lime in the cement to form calcium silicate hydrate (C-S-H) products. In contrast with other SCMs, glass is siliceous and thus the reaction can also cause alkali silica reaction (ASR) which causes expansion and cracking. This study was completed in order to characterize the chemical reactions and their rate using a simplified system that mimics glass particles in hardened cement paste.</p> <p>Silica powder was added to solutions containing calcium hydroxide and/or sodium hydroxide. The rate of dissolution of the silica was monitored as well as the composition of the reaction products. Dissolution rates of silica with varying concentrations of silica, calcium hydroxide and sodium hydroxide, were fitted to the Hixson-Crowell cubic root law. The precipitate composition of the reaction product was represented by means of triaxial plots. It was found that silicate ions enter the solutions containing sodium hydroxide and containing both sodium hydroxide and calcium hydroxide. The rate is proportional to the quantity of sodium ions in the solution and to the pH. Also, higher concentrations of silica generally cause higher dissolution rates. The solutions with a pH of 13.48 and with lower silica concentrations created reaction products that were similar to C-S-H while the solutions with higher pH levels formed ASR after thirty days. The C-S-H prevented further dissolution of the silica. The formation of the ASR reaction products did not prevent further dissolution of the silica and they continued to dissolve until most of the silica had entered the solution.</p> / Master of Applied Science (MASc)
92

Modeling, Analysis, and Design of Subcarrier Multiplexing on Multimode Fiber

Kanprachar, Surachet 11 April 2003 (has links)
This dissertation focuses on the use of subcarrier multiplexing (SCM) in multimode fibers, utilizing carrier frequencies above what is generally utilized for multimode fiber transmission, to achieve high bit rates. In the high frequency region (i.e., frequencies larger than the intermodal bandwidth), the magnitude response of multimode fiber does not decrease monotonically as a function of the frequency but is shown to become relatively flat (but with several deep nulls) with an amplitude below that at DC. The statistical properties of this frequency response at high frequencies are analyzed. The probability density function of the magnitude response at high frequencies is found to be a Rayleigh density function. The average amplitude in this high frequency region does not depend on the frequency but depends on the number of modes supported by the fiber. To transmit a high bit rate signal over the multimode fiber, subcarrier multiplexing is adopted. The performance of the SCM multimode fiber system is presented. The performance of the SCM system is significantly degraded if there are some subcarriers located at the deep nulls of the fiber. Equalization and spread spectrum techniques are investigated but are shown to be not effective in combating the effects of these nulls. To cancel the effects of these deep nulls, training process and diversity coding are considered. The basic theory of diversity coding is given. It is found that the performances of the system with training process and the system with diversity coding are almost identical. However, diversity coding is more appropriate since it requires less system complexity. Finally, the practical limits and capacity of the SCM multimode fiber system are investigated. It is shown that a signal with a bit rate of 1.45 Gbps can be transmitted over a distance up to 5 km. / Ph. D.
93

Addressing Europe’s Declining Fertility Rates : A Case Study of Housing Support Policy in Hungary

Podör, Anna, Skracic, Antonia January 2024 (has links)
Declining fertility rates are an increasingly important topic in today’s Europe. Fertility rates play a significant role in sustaining a stable population and ensuring economic growth and innovation. The purpose of this thesis is to evaluate the effectiveness of CSOK, a Hungarian housing policy specifically aimed at increasing fertility rates. The research relies on theories such as Becker’s new home economics theory, Quantity-quality trade-off theory, and Willis’s economic theory of family. The study of housing prices and fertility is also provided to understand the relationship between housing and fertility better. The benchmark country for this thesis is Hungary. Using the Synthetic Control Method (SCM), we construct a synthetic Hungary to match pretreatment outcomes closely. The findings of this thesis show that the policy has no positive effect on fertility rates and is inefficient in spending government resources. The study highlights the significance of governmental trust, emphasizing the importance of stable economic conditions and a family-friendly environment to effectively increase fertility rates.
94

Klimatreducerad betong med slagg : Inverkan av accelererande tillsatsmedel / Climate-enhanced concrete with slag : Influence of accelerating additives

Backlund, Erik, Liberg, Henrik, Karlsson, Malte January 2024 (has links)
Betong är världens mest använda byggnadsmaterial och en stor utsläppskälla av koldioxid. Det är framför allt produktion av cementet i betongen som bidrar till koldioxidutsläppen. Globalt sett är produktionen av cement den tredje största orsaken till koldioxidutsläpp, 8 % av världens utsläpp. Därför ligger det stort intresse i att minska mängden cement i betongen för att nå lägre klimatpåverkan. Ett sätt att göra detta på är att delvis byta ut cementet mot andra tillsatsmaterial med cementliknande egenskaper, till exempel slagg. Det största problemet med detta är att betongens härdningstid förlängs. Detta arbete genomförs tillsammans med RISE för att hjälpa Hedareds Sand och Betong att ställa om till klimatförbättrad betong i sina prefabelement. För att göra detta måste härdningstiden i den klimatförbättrade betongen sänkas. Denna studie ska därför undersöka om accelererande tillsatsmedel kan korta härdningstiden i slaggbetong. För att undersöka detta användes två experimentella metoder: isotermisk kalorimetri och gjutning med tryckprovning. Resultatet från den isotermiska kalorimetrin visade att acceleratorn Master X-Seed 140 gav kortast induktionsperiod och klart högre värmeflöde än referensprovet. Resultatet från gjutningen visade att den prövade betongen nådde en tryckhållfasthet på 29,73 MPa efter 24 timmar. Vilket är 62,5 % högre än referensprovet utan accelerator och tydligt över kravet på 16 MPa efter 24 timmar. Slutsatsen som gick att dra efter detta arbete var att acceleratorn visade mycket god effekt på tryckhållfastheten och ger utökade möjligheter att använda klimatförbättrad betong inom prefabindustrin. / Concrete is the world's most widely used building material and a significant source of carbon dioxide emissions. It is primarily the production of cement in concrete that contributes to these emissions. Globally, cement production is the third-largest contributor to carbon dioxide emissions, accounting for 8 % of the world's emissions. Therefore, there is considerable interest in reducing the amount of cement in concrete to achieve lower climate impact. One way to do this is by partially replacing cement with other supplementary materials with cement-like properties, such as slag. The main challenge with this approach is that it extends the curing time of the concrete. This work is conducted in collaboration with RISE to assist Hedareds Sand and Betong in transitioning to climate-enhanced concrete in their precast elements. To achieve this, the curing time in the climate-enhanced concrete must be reduced. This study aims to investigate whether accelerating admixtures can shorten the curing time in slag concrete. Two experimental methods were used to investigate this: isothermal calorimetry and casting with pressure testing. The results from isothermal calorimetry showed that the accelerator Master X-Seed 140 had the shortest induction period and significantly higher heat flow than the reference sample. The results from casting showed that the tested concrete reached a compressive strength of 29,73 MPa after 24 hours, which is 62,5 % higher than the reference sample without accelerator and clearly exceeds the requirement of 16 MPa after 24 hours. The conclusion drawn from this work was that the accelerator demonstrated a very good effect on compressive strength and provides expanded opportunities for using climate-enhanced concrete in the precast industry.
95

Sustainability through Buyer-Supplier Relationships : A Qualitative Study about Buyer- Supplier influences on Supply Chain Sustainability in Swedish SMEs

Björkman, Folke, Green, Jonathan January 2024 (has links)
This thesis looks at the challenges of establishing environmentally sustainable supply chains in Swedish Small and Medium Enterprises (SMEs) through the lens of buyer-supplier relationships. Despite SMEs' important role in innovation and employment, there is little research on sustainability in this sector, particularly on buyer-supplier dynamics. Existing literature emphasizes the potential benefits of strong buyer-supplier relationships but does not investigate into their role in SME sustainability efforts. This study aims to fill this gap and provide insights into the barriers to sustainable supply chain development in Swedish SMEs. It aims to educate policymakers and practitioners about the importance of fostering long-term partnerships within SME supply chains. The purpose of this study is to explore how buyer-supplier relationships influence sustainable practices in the supply chains of Swedish SMEs. Utilizing qualitative research methods, the research involved interviews with multiple SMEs to gather insights into the dynamics of these relationships and their effect on sustainability efforts. The study examines the role of trust, communication, and mutual sustainability goals in strengthening these relationships. The findings indicate that robust, trust-based buyer-supplier relationships are essential for fostering sustainable supply chain practices. Such relationships enable better collaboration, which is crucial for SMEs aiming to overcome limitations related to their size and bargaining power. The study also shows that a variety of factors influence SMEs' efforts to become more environmentally sustainable. Examples include industry, customer and supplier size, and new regulations. This thesis contributes to the literature by describing specific challenges and effective practices relevant to Swedish SMEs and suggests that enhancing the quality of buyer-supplier interactions can significantly impact their sustainability outcomes. Practical recommendations are offered for SMEs to optimize their supply chain sustainability, highlighting the importance of strategic partnerships in achieving environmental goals.
96

"Modelo de avaliação do processo de gerência de configuração de software" / "Evaluation model of software configuration management process"

Cia, Thais Miranda 10 May 2006 (has links)
A gerência de configuração vem sendo estudada desde os anos sessenta. Inicialmente, era aplicada da mesma forma para software e hardware, sendo que no final dos anos setenta já havia padrões de gerência de configuração específicos para software. Com a crescente demanda por qualidade de software, as práticas de gerência de configuração vem sendo cada vez mais utilizadas no desenvolvimento de software, uma vez que a gerência de configuração de software é um dos processos fundamentais para se ter qualidade no desenvolvimento e manutenção de software. Embora cada vez mais amplamente utilizado, não existe um consenso de práticas e nomenclaturas sobre as práticas de gerência de configuração. Dessa forma, o objetivo deste trabalho é elaborar um modelo de avaliação do processo de Gerência de Configuração, que permite avaliar as práticas e processos fundamentais para a implantação da gerência de configuração, levando em consideração as práticas e processos descritos nas principais normas internacionais de desenvolvimento de software. Esse modelo de avaliação também permite que as ferramentas disponíveis para gerência de configuração sejam avaliadas, identificando quais práticas e processos elas auxiliam na execução. / The Configuration Management has been studied since the 70’s. In the beginning it was applied in the same way for software and hardware, but in the late 70’s there were some specific configuration management patterns defined for software. The demand for software quality has increased recently, this way the configuration management practices have been more used in software development, because the software configuration management is one of the most important processes to assess quality during software development or maintenance. Although its use is increasing, there is no consensus about the configuration management practices and the names applied to them. The objective of this work is to elaborate an evaluation model for configuration management process, to evaluate the practices and the fundamental processes to perform configuration management, based on the most important software development standards. This evaluation model can also be used to evaluate configuration management tools, identifying what practices and process it help to execute.
97

"Modelo de avaliação do processo de gerência de configuração de software" / "Evaluation model of software configuration management process"

Thais Miranda Cia 10 May 2006 (has links)
A gerência de configuração vem sendo estudada desde os anos sessenta. Inicialmente, era aplicada da mesma forma para software e hardware, sendo que no final dos anos setenta já havia padrões de gerência de configuração específicos para software. Com a crescente demanda por qualidade de software, as práticas de gerência de configuração vem sendo cada vez mais utilizadas no desenvolvimento de software, uma vez que a gerência de configuração de software é um dos processos fundamentais para se ter qualidade no desenvolvimento e manutenção de software. Embora cada vez mais amplamente utilizado, não existe um consenso de práticas e nomenclaturas sobre as práticas de gerência de configuração. Dessa forma, o objetivo deste trabalho é elaborar um modelo de avaliação do processo de Gerência de Configuração, que permite avaliar as práticas e processos fundamentais para a implantação da gerência de configuração, levando em consideração as práticas e processos descritos nas principais normas internacionais de desenvolvimento de software. Esse modelo de avaliação também permite que as ferramentas disponíveis para gerência de configuração sejam avaliadas, identificando quais práticas e processos elas auxiliam na execução. / The Configuration Management has been studied since the 70’s. In the beginning it was applied in the same way for software and hardware, but in the late 70’s there were some specific configuration management patterns defined for software. The demand for software quality has increased recently, this way the configuration management practices have been more used in software development, because the software configuration management is one of the most important processes to assess quality during software development or maintenance. Although its use is increasing, there is no consensus about the configuration management practices and the names applied to them. The objective of this work is to elaborate an evaluation model for configuration management process, to evaluate the practices and the fundamental processes to perform configuration management, based on the most important software development standards. This evaluation model can also be used to evaluate configuration management tools, identifying what practices and process it help to execute.
98

Interna flöden och processer på Å&R Carton : processbaserad verksamhetsanalys och förbättringsförslag för ledtidsreduktion / Internal Processes at Å&R Carton : Process Based Analys and Proposals to Reduce Time in the Supply Chain

Gustafson, Anders January 2003 (has links)
<p>Denna rapport syftar till att, på Å&R Carton i Norrköping, analysera de interna flödena och processerna samt ge förslag på hur ledtider ska kunna reduceras väsentligt. Ett sätt att uppfylla syftet är att dela in verksamheten i processer genom olika metoder och kriterier förprocessbestämning. Valda metoder i rapporten är; kvalitativ ansats med hög validitet och reliabilitet, processbaserad verksamhetsanalys och procedurbeskrivning. </p><p>Genom omfattande litteraturstudier, insamlande av data i form av intervjuer, benchmarking, platsundersökningar och interna dokument har nulägesmodeller arbetats fram. Analysen av dessa visar bland annat på att såväl planeringsprocessen som inköpsprocessen idag inte fungerar värdeadderande och bör ses över. Därutöver finns också andra processer som bidrar till ett komplext flöde. Dessa behöver effektiviseras eller ändras för att korta ledtider. Vidare visar analysen på att en omfattande attitydsundersökning behövs, dels för att komma till rätta med vissa stämningar och dels för att på sikt skapa en effektiv arbetsmiljö. </p><p>Till förbättringsförslagen hör, förutom en attitydsundersökning, förslaget att utarbeta tydliga mål och strategier. Sedan måste dessa kommuniceras till samtliga anställda, till exempel genom arbetsgrupper. Vidare föreslås att Å&R Carton tittar på automatisk datafångst som ett mycket kostnadseffektivt sätt att kontrollera det totala flödet. På lång sikt bör också företaget titta på att implementera processorientering. Dock behöver företaget först och främst se till att skapa en förändringsvillig attityd för att nå framgång i sitt effektiviseringsarbete. Slutsatsen blir att Å&R Carton har stor potential att väsentligt förkorta sina ledtider om företaget hanterar situationen rätt. För att lyckas kan delar av denna rapport användas där det viktigaste är att en engagerad ledning visar vägen. </p> / <p>The purpose of this final thesis is to analyse the internal processes at Å&R Carton in Norrköping and give proposals to reduce time in the Supply Chain. One way to fulfill the purpose is to use Process Based Analys and split the organisation in different processes. Process Based Models have then been constructed by studying litterature, benchmarking, internal documents and making a lot of interviews. The analys shows that different processes must be changed to make the flow through the Supply Chain more efficient. The analys give us also recommendations like attitude investigations and implementation of ECR. The conclusion is that Å&R Carton have great potential to reduce time in the Supply Chain if the management are active, follow the recommendations and show the employees the way about.</p>
99

Interna flöden och processer på Å&amp;R Carton : processbaserad verksamhetsanalys och förbättringsförslag för ledtidsreduktion / Internal Processes at Å&amp;R Carton : Process Based Analys and Proposals to Reduce Time in the Supply Chain

Gustafson, Anders January 2003 (has links)
Denna rapport syftar till att, på Å&amp;R Carton i Norrköping, analysera de interna flödena och processerna samt ge förslag på hur ledtider ska kunna reduceras väsentligt. Ett sätt att uppfylla syftet är att dela in verksamheten i processer genom olika metoder och kriterier förprocessbestämning. Valda metoder i rapporten är; kvalitativ ansats med hög validitet och reliabilitet, processbaserad verksamhetsanalys och procedurbeskrivning. Genom omfattande litteraturstudier, insamlande av data i form av intervjuer, benchmarking, platsundersökningar och interna dokument har nulägesmodeller arbetats fram. Analysen av dessa visar bland annat på att såväl planeringsprocessen som inköpsprocessen idag inte fungerar värdeadderande och bör ses över. Därutöver finns också andra processer som bidrar till ett komplext flöde. Dessa behöver effektiviseras eller ändras för att korta ledtider. Vidare visar analysen på att en omfattande attitydsundersökning behövs, dels för att komma till rätta med vissa stämningar och dels för att på sikt skapa en effektiv arbetsmiljö. Till förbättringsförslagen hör, förutom en attitydsundersökning, förslaget att utarbeta tydliga mål och strategier. Sedan måste dessa kommuniceras till samtliga anställda, till exempel genom arbetsgrupper. Vidare föreslås att Å&amp;R Carton tittar på automatisk datafångst som ett mycket kostnadseffektivt sätt att kontrollera det totala flödet. På lång sikt bör också företaget titta på att implementera processorientering. Dock behöver företaget först och främst se till att skapa en förändringsvillig attityd för att nå framgång i sitt effektiviseringsarbete. Slutsatsen blir att Å&amp;R Carton har stor potential att väsentligt förkorta sina ledtider om företaget hanterar situationen rätt. För att lyckas kan delar av denna rapport användas där det viktigaste är att en engagerad ledning visar vägen. / The purpose of this final thesis is to analyse the internal processes at Å&amp;R Carton in Norrköping and give proposals to reduce time in the Supply Chain. One way to fulfill the purpose is to use Process Based Analys and split the organisation in different processes. Process Based Models have then been constructed by studying litterature, benchmarking, internal documents and making a lot of interviews. The analys shows that different processes must be changed to make the flow through the Supply Chain more efficient. The analys give us also recommendations like attitude investigations and implementation of ECR. The conclusion is that Å&amp;R Carton have great potential to reduce time in the Supply Chain if the management are active, follow the recommendations and show the employees the way about.
100

e-Supply Chain Management Study on Taiwan Flat Cold-Rolled Steel Industry

Shih, Meng-Hsun 20 May 2002 (has links)
Taiwan steel industry has stepped from grown-up into mature period. Especially, the midstream and downstream of steel industries will face the problems of sterner challenges and overcapacity, because of the oversupply of global steel. Not only the prices of oil, coal, water and power have climbed, but also the shipping cost has increased continuously. The improvement of Supply-Chain-Management (SCM) has become a significant issue under the circumstances. The SCM of Taiwan flat cold-rolled steel industry is different from the other ones that it doesn¡¦t use BOM. The main feature of Technical System ¡V ¡§Standard of Operation¡¨(SOP) is the kernel module that links the sales order entry, production management, purchasing, ¡Ketc. The production type is to input a sole coil and output many sub-coils. It is not like the electronic industry to assemble many parts on a product. It only coats the surface of steel with microelements, such as oil, zinc, aluminum and paint. The feature makes it impossible to apply SCM or ERP package directly on this industry. The procedures of this study are mainly through the interview of steel companies, and review on the relevant reference documents related to the subject of those have been published domestically and internationally, meanwhile to get a better understanding on the most recent development of Supply Chain Management and e-business of steel industry. Besides, through the comparison of the similar companies, it is likely to understand the associated topics and models on the SCM and e-Business for flat cold-rolled steel industry. The key point is to analyze the characters of supply chain system of Taiwan cold-rolled steel industry and consider the features of flat cold-rolled steel ¡V SOP and coil- based Standard Cost system, to establish an appropriate e-SCM model, exploring the suitable information technologies and applications to improve the drawbacks of present SCM. Finally, to make a recommendation for the industry as their reference when they plan for the implementation of e-SCM.

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