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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.

Long-term multi-objective project selection under uncertainty

Durmus, Beste Gul 09 November 2007 (has links)
No description available.

Life-cycle cost study of ground source heat pumps in hot humid climate zone

Canbek, Cetin 10 November 2010 (has links)
Ground source heat pump (GSHP) systems are gaining recognition as a cost effective and green heating, ventilating and air conditioning (HVAC) alternative in the United States. Still, this technology is not highly utilized due to factors such as high initial investment, lack of confidence and uncertainties in cost items. This study focuses on the reflection of the variations in cost items on the feasibility and life-cycle cost of a typical GSHP system. For this purpose, life-cycle costs were calculated for a typical GSHP system and cost data was gathered for several projects. Possible variations on cost variables are defined. Then, the effect of these variations on life cycle cost is analyzed on a comparative basis with a conventional system. It was concluded that the GSHP systems may not be economically favorable over a conventional HVAC systems without current incentives in hot and humid climate regions.

A lessons learned document for disputes in Florida Department of Transportation projects

Cinkilic, Cagri 13 November 2009 (has links)
The purpose of this research is to identify, analyze and evaluate the current Florida Department of Transportation (FDOT) reports in DRB database and develop a utilized, user friendly lessons learned document for FDOT and contractor. The analysis of the reports in the DRB database illustrated that, most common disputes in governmental transportation projects in Florida are due to unforeseen conditions. Over the course of this research, lessons were developed according to the recommendations made by DRB agents at the end of each case in 262 reports. Parties involved in a FDOT project can check this document to avoid recurrence of the negative outcomes and promote recurrence of the positive outcomes.

Utveckling av säte till kulventil SKV

Jansson, Daniel, Andersson, Lennart January 2007 (has links)
<p>This report contains a degree project made by the mechanical engineering students Lennart Andersson and Daniel Jansson. The project has performed in assignment by SOMAS Valves AB in Säffle. SOMAS are leading in development on control and on/off valves. To maintain this position they always want to improve their products. One way in this development is valves that are more tightened.</p><p>The purpose with our project was to investigate another seat design on a HiCo (High Cobalt Alloy) seat to a SKV 150 PN 25 valve and compare this to an original HiCo seat.</p><p>By modifying the seat on a ball valve we want to achieve a valve that leaks lesser then a valve whit original seat. At the same time the maneuver torque should be retained or better and the wear should not be worse.</p><p>The project begins with a theoretic investigation of valve forces, maneuver torque and seat design. A manufacturing drawing was made in Pro ENGINEER and handed over to SOMAS AB for manufacturing. Four seats are made in the new design and will be compared with four original seats about maneuver torque, tightened and wear. The idea to make a trace in the middle of the seat was that it would tighten earlier.</p><p>Water under pressure is pressed against the valve to test its resistance of leaking, the leaking is measured by a measure glass. The modified seats leaks more then the original seats, even though, according to the theory they should have a higher seat force. Even the maneuver torque is higher on the modified seats, but this increase is not a problem. All seats was tested to watch their resistant to wear, to test this, a valve mounted with seats is opened and closed 600 times (about 3hours). Because of the short wear time it’s hard to see and validated wear, but on the after coming pressure test the valve is more tightened.</p><p>A reason to leaking is the tolerances between the seats and the ball. The reason why the modified valve seat leaks more is probably that the lathe area functions as a channel for the medium.</p><p>The medium which passes the first tightened area can easier find a new way to pass the second tightened area.</p><p>The conclusion is that the new seat design is nothing to go further with, but there are proposals for a new seat design.</p>

Undersökning av svetsförband med avseende på svetsgeometri, diskontinuiteter och blästring med stålkulor / An Examination of Welded Joints Regarding Weld Geometry, Weld Discontinuities and the Effects of Shot Peening

Bergdahl, Stefan January 2006 (has links)
<p>Breakdowns of welded structures are usually a consequence of fatigue loading. Fatigue fractures are commonly initiated in the region close to the weld toe but can also initiate from the weld root and from discontinuities inside the weld. The purpose of this investigation was to examine the weld quality of welded joints produced at Volvo Wheel Loaders factory in Arvika. The goal of the investigation is to give a clearer insight regarding factors influencing the fatigue strength of the welded joints and thereby give a better foundation for fatigue strength calculations.</p><p>The investigation is including examination of the weld geometry, weld discontinuities and the effects of shot peening. Mainly three different methods for collecting test data have been used: Plastic replicas cast on the weld profile, weld specimens from a rear frame belonging to a wheel loader of model L110E/120E and Almen testing of the shot peening.</p><p>The results showed that it is not possible to control even transition between the weld material and the base material without after treatment. The most frequent reason why the welded joints did not fulfill the demands in the Volvo Corporate Standard was leg deviation outside the acceptable limit. The most frequent weld defect was lack of fusion inside the weld. The occurrence of this defect was overrepresented in butt welds. The results also showed that the fatigue enhancing effects of shot peening are with today’s process just being used to a minor degree.</p>

Kostnadseffektivisering av bärcylinder

Andersson, Andreas, Andersson, Anders January 2007 (has links)
<p>Rapporten avser ett examensarbete inom maskiningenjörsprogrammet vid Karlstad universitet, uppdragsgivaren är Metso Paper Karlstad AB.</p><p>Metso Paper tillverkar tissuemaskiner för pappersindustrin och utför även service samt utveckling av dessa produkter. Tissue är mjukpapper och med detta avses hygienpapper och servetter. Fokus i uppgiften var att kostnadseffektivisera bärcylindern, vilken är en ingående komponent i tissuemaskinen. Bärcylindern är en vals som sitter monterad i slutet på maskinen, i det område där det färdiga papperet rullas upp på spolar. De analyserade objekten har dimensionerna; diameter 900mm med längden 2825mm samt diameter1100mm med längden 5550mm.</p><p>Inledningsvis analyserades bärcylinderns huvudfunktioner, vilka kan sammanfattas:</p><p>• Att med vakuum transportera spetsen (smal pappersbana) från spetsblåsningsrännan till anläggningsytan mellan bärcylinder och upprullningsspole.</p><p>• Att stödja pappersbanan under upprullning på spole.</p><p>• Att skapa ett anläggningstryck mot upprullningsspolen så att ett drivande moment uppstår. Moment krävs då upprullningsspolen saknar drivning.</p><p>Uppgiften delades in i två delar för ett enklare tillvägagångssätt, ”nykonstruktion” samt ”förbättring och effektivisering av befintlig konstruktion”</p><p>Nykonstruktion behandlar hållfasthetsberäkning av godstjocklek samt val av alternativa material. Förbättring och effektivisering berör hur den nuvarande konstruktionen kan förenklas och tillverkningsprocessen förbättras. Resultatet påvisar att dagens konstruktion är onödigt överdimensionerad, godstjockleken kan reduceras med bibehållna funktionsegenskaper. Att tillverka mantel i stål istället för gjutgods ger lägre inköpskostnad av material för bärcylinder i diameter 900mm, vid inköp av två mantlar på en gång halveras nästan materialkostnaden.</p><p>För att kunna effektivisera den befintliga konstruktionen och tillverkningsprocessen måste vissa delar av gjutningen utföras med högre noggrannhet, kriterier såsom: godstjocklek, rundhet samt närvaro av restprodukter bör beaktas. Detta för att effektivisera den efterföljande skärande bearbetningen.</p><p>Slutgiltigen finns stor potential att kostnadseffektivisera denna produkt med en kombination av dimensionering, materialval samt effektivare bearbetningsprocess.</p> / <p>The report intends a thesis work within the machine engineer program at Karlstad University, the employee is Metso Paper Karlstad AB</p><p>Metso Paper produces tissue machines for the paper industry and also performs service and development of these products. Tissue is soft paper which includes hygiene paper and table napkins. Focus in the task is to reduce the cost of the reel drum, which is a detailed component in a tissue machine. The reel drum is a drum which is assembled in the end on the paper machine, in the area where the paper is rolled up on spools. The analyzed items have the dimensions; diameter 900mm with the length 2825 mm and diameter1100 mm with the length 5550mm.</p><p>Initially, the reel drum’s main functions were analyzed, which can be summarized:</p><p>• That with vacuum transport the point (narrow paper chute) from the point swindle groove to the surface between the reel drum and the reel spool</p><p>• To support paper during winding on the reel spool</p><p>• To create a pressure against the reel spool so that a driven torque arises. The torque is required because the reel spool has no own power supply.</p><p>The task was divided in two parts for a simpler procedure,” new structure” and ”improvement and efficiency improvement of existing structure”</p><p>New structure treats calculations concerning the thickness of the shell and choices of alternative materials. Improvement and efficiency concerns how the current structure can be simplified and the production process improved. The result demonstrates that today's structure is unnecessary thick, the shell thickness l can be reduced with maintained function properties. To produce the shell in steel instead of cast iron gives lower purchase cost of materials for reel drums in diameter 900mm, buying to shells at the time almost reduces the material cost with 50%</p><p>In order to make the existing structure and the production process more effective must certain parts of the casting be carried out with higher precision, criteria such as: thickness, roundness and presence of rest products should be taken into consideration. Higher casting precision makes the following machine work easier.</p><p>Finally there exists a big potential to reduce the cost of the reel drum. Important criteria’s that is to be considered are: dimensions, materials and more effective processing.</p>

Producktutveckling av mekanisk slitter

Rudby, Peter, Andersson, Erik January 2007 (has links)
<p>Sammanfattning</p><p>Vår uppdragsgivare Metso Paper Karlstad AB är världsledande inom tillverkning av Tissue maskiner (tunn papper). Av Metso Paper fick vi uppgiften att utveckla en Mekanisk Slitter. En mekanisk slitter sitter monterad i slutet av en tissue maskin och har uppgiften att dela pappersbanan i flera delar beroende på hur många slittrar man valt att installera. Varför man delar pappersbanan är för att underlätta efterhanteringen av rullarna.</p><p>Problemet med dagens Mekaniska Slitter är att den inte klarar av de säkerhetskrav som ställs för att få kunna vistas i området där den är installerad. Avståndet som klingan är oskyddad är för stort. Enligt EN 294:1992 skapar dagens utformning ett säkerhetsavstånd på 850mm. Uppgiften presenteras i följande kravspecifikation:</p><p>• Slittern ska konstrueras om med hänsyn tagen till gällande säkerhetsavstånds för att möjliggöra passage under drift.</p><p>• Konstruera för att underlätta underhåll</p><p>• Kostnadseffektivisera sidledsrörelsen</p><p>• Kostnadseffektivisera inmätning i sidled</p><p>• Minimera priset</p><p>Resultatet från kravspecifikation resulterade i följande utformning:</p><p>"Bilder"</p><p>Avståndet mellan det överliggande banföringsstödet och linskyddet dvs det avstånd som klingan är oskyddad är nu 19 mm, enligt EN 294:1992 generar det i ett säkerhetsavstånd på 120 mm detta leder till att man kan vistas i området under drift. Styrningen av linsen möjliggjordes genom at vi nu styr motor och lins linjärt, på föregående modell va det ett enda fast skydd som inte kunde regleras, samt att motor styrdes kring en punkt.</p><p>Sidleds rörelsen med inmätning har vi valt att köpa in detaljer för detta ändamål, på dagens slitter är dessa komponenter egentillverkade och kostar då oerhört mycket i tillvekning. Priset för den ny konstruerade Slittern blev 15000 kr billigare vilket är ett mycket gott resultat</p> / <p>Abstract</p><p>Our commissioner Metso Paper Karlstad AB is world leaders in manufacturing Tissue machines (thin paper machine). Metso Paper gave us the commission to develop a Mechanical slitter. A mechanical slitter are being placed in the ending part of a tissue machine and its assignment is to spilt paperboard in to several peaces depending on how many that are installed. The reason by splitting the board is make it fit in the after handling (conversion machine).</p><p>The problem with the Slitter today is that it doesn’t satisfy the security demands concerning the ability to use the area around the slitter when it’s in operation mode. The security distance depends on the blade and the distances that it’s not covered. According to EN 294:1992 the safety distance is 850mm. The assignment is present in a demandspecification:</p><p>• The Slitter will be constructed considered the security demands to make It possible be around the slitter when its in use.</p><p>• Construct for simplified maintenance.</p><p>• Coastefficient the sidemovements</p><p>• Coastefficient the measurements in sidemovments</p><p>• Minimize the price</p><p>These demands ended up in following result:</p><p>"Pictures"</p><p>The distance between the overlaid papersupport and the linscover has now been reduced; it’s only 19mm and will make it possible to use the area around the slitter. According to EN 294:1992 the safety distance now is 120mm. The ability to steer the linscover render possible by steering the engine linear. On today’s model there is only one fixed cover, and the engine is steered from one fixed point and result in a non linearmotion. Concerning the sidemovment and its measurements we decide to buy it all, because today’s components are manufactured by them selves and are really expensive.</p><p>Our new construction ended up 15000kr cheaper then today’s siltter and we think it’s a really good result.</p>

Kylskåpsinredning : Praktiska funktioner

Andersson, Mattias January 2008 (has links)
No description available.

Design Considerations for Reinforced Concrete Masonry Walls Regarding Moment Magnification

Cowart, Jarred Wade 01 May 2007 (has links)
Currently, regardless of the height of a reinforced masonry wall, engineers are required to consider moment magnification when using strength design provisions. An attempt at finding reasonable h/r limits for consideration of moment magnification is explored. Moment-curvature diagrams were developed using a spreadsheet to define the behavior of 8 inch and 12 inch concrete masonry walls. A series of models were created with axial load, out-of-plane load, height, reinforcing, and wall width as variables. The models were loaded out-of-plane in a finite element program until failure. The results were organized to produce the moment magnification of each wall. Results were summarized to determine height to radius of gyration (h/r) ratio limits for consideration of moment magnification. For walls with axial loads over 5% of the compressive strength times the cross sectional area, practical limits were not found. The limits corresponded to short walls that would not aid engineers in design. For those walls with axial load of 5% and less, walls with h/r ratios of 24 or less would not have to consider the effects of moment magnification, walls with h/r ratios between 24 and 40 would use a simplified method of increasing the static moment by 10%, and walls with h/r ratios over 40 would have to consider current moment magnification procedures.

Evaluation, Comparison, and Design of Two Experimental Bridges in Tennessee

Scoble, Kyle Parker 01 August 2007 (has links)
This thesis describes the design and evaluates the adequacy of the moment connection of an experimental two-span highway bridge designed by the Tennessee Department of Transportation. The Massman Drive bridge is an experimental design that unifies the construction economy of simple span bridges and the structural economy of continuous span bridges. The experimental connection, consisting of cover plates and kicker wedge plates, is used to connect the two adjoining girders over the center pier. As a result, the bridge is designed to function as a continuous bridge during the deck pour and behave compositely with the reinforced concrete deck under the live load. After completing a moment comparison analysis, it is concluded that the Massman Drive bridge indeed acts as continuous over the pier as it was designed. This thesis also compares the measured lateral wheel load distribution factors for two experimental two-span highway bridges designed by the Tennessee Department of Transportation. The measured load distribution factors were then compared to distribution factors from several methods commonly in use such as AASHTO 1996, AASHTO 2001 LRFD, and Henry’s Method. Results from American Association of State Highway and Transportation Officials (AASHTO) 1996 produced load distribution factors that were deemed to be conservative. Interior girder load distribution factors from both the DuPont Access and Massman Drive bridges compared well to the AASHTO 2001 Load and Resistance Factor Design (LRFD) specifications. Exterior girder distribution factors compared well with Henry’s Method, while the values from AASHTO were consistently high. Also, the factors were consistent between the Massman Drive and DuPont Access bridges.

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