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Rotorcraft transmission design is limited by empirical weight trends that are proportional to the power/torque raised to the two-thirds coupled with the relative inexperience industry has with the employment of variable speed transmission to heavy lift helicopters of the order of 100,000 lbs gross weight and 30,000 installed horsepower. The advanced rotorcraft transmission program objectives are to reduce transmission weight by at least 25%, reduce sound pressure levels by at least 10 dB, have a 5000 hr mean time between removal, and also incorporate the use of split torque technology in rotorcraft drivetrains of the future. The major obstacle that challenges rotorcraft drivetrain design is the selection, design, and optimization of a variable speed transmission in the goal of achieving a 50% reduction in rotor speed and its ability to handle high torque with light weight gears, as opposed to using a two-speed transmission which has inherent structural problems and is highly unreliable due to the embodiment of the traction type transmission, complex clutch and brake system. This thesis selects a nontraction pericyclic continuously variable transmission (P-CVT) as the best approach for a single main rotor heavy lift helicopter to target the above mentioned obstacle for drivetrain design and provides advancement in the state of the art of drivetrain design over existing planetary and split torque transmissions currently used in helicopters. The goal of the optimization process was to decrease weight, decrease noise, increase efficiency, and increase safety and reliability. The objective function utilized the minimization of the weight and the constraint is the tooth bending stress of the facegears. The most important parameters of the optimization process are weight, maintainability, and reliability which are cross-functionally related to each other, and these parameters are related to the torques and operating speeds. The analysis of the split torque type P-CVT achieved a weight reduction of 42.5% and 40.7% over planetary and split torque transmissions respectively. In addition, a 19.5 dB sound pressure level reduction was achieved using active gear struts, and also the use of fabricated steel truss like housing provided a higher maintainability and reliability, low cost, and low weight over cast magnesium housing currently employed in helicopters. The static finite element analysis of the split torque type P-CVT, both 2-D and 3-D, yielded stresses below the allowable bending stress of the material. The goal of the finite element analysis is to see if the designed product has met its functional requirements. The safety assessment of the split torque type P-CVT yielded a 99% probability of mission success based on a Monte Carlo simulation using stochastic- petri net analysis and a failure hazard analysis. This was followed by an FTA/RBD analysis which yielded an overall system failure rate of 140.35 failures per million hours, and a preliminary certification and time line of certification was performed. The use of spherical facegears and pericyclic kinematics has advanced the state of the art in drivetrain design primarily in the reduction of weight and noise coupled with high safety, reliability, and efficiency.

<p>Vad är viktigt när hyllsystem till butiker ska säljas, tillverkas och användas? Jo de måste vara användarvänliga alltså lätta att montera, bära och modifiera. De bör även vara smidiga att frakta, de ska då vara lätta (viktmässigt) och inte otympliga. Framförallt måste de vara prisvärda alternativt billiga att köpa, för att uppnå detta bör de bestå av så lite material som möjligt samtidigt som de ska vara lätta att producera.</p><p>Detta var några av de frågeställningar som detta arbete utgått ifrån och de har penetrerats mer eller mindre grundligt.</p><p>För att svara på detta så undersöktes möjligheten att ändra godstjockleken i stolparna till hyllsystemet från 2,5 mm till 2,0 mm, detta skulle vara delvis lösningar till både vikt- och materialfrågan men framförallt prisfrågan då materialet står för en stor del av kostnaden. Detta framkom genom att de olika stolparna räknades på ur flera olika synvinklar för att reda ut om de skulle hålla för denna typ av förändring. De aspekter som bearbetades var böjning av stolpen, att hålen skjuvas sönder (konservburksöppnar-effekt) av krokarna till hyllkonsol och lösfot. Det resultat som framkom var, på vissa storlekar kan förändringen göras utan eftertanke medan på de mindre stolparna krävs lite mer funderande och kanske några praktiska tester innan beslut fattas. Den aspekt som är mest dimensionerande är att stolpen böjs av.</p><p>I och med att användarvänligheten alltid kan förbättras arbetades en lathund fram. Denna lathund är tänkt att slutanvändaren ska ha som hjälpmedel för att kunna lasta varor på hyllorna på rätt sätt, alltså inte överlasta och riskerar att det rasar.</p><p>För att reda ut hur Itab´s system står sig gentemot sina konkurrenter på dessa viktiga punkter utfördes även en konkurrentanalys. Det som testades var främst stabiliteten, monteringsvänligheten och om det fanns några uppenbara skaderisker med stativen. Tyvärr så var det svårt att få fram alla konkurrenter som skulle testas, än viktigare var att Itab´s egna inte var tillgänglig så en jämförelse var inte möjlig, men de konkurrenter som var intresserade av att ha med sina stativ fick gärna det så ett test utfördes. Frågan gällande priset testades inte då denna rapport inte riktar sig till slutanvändaren.</p> / <p>What is the most important aspect when shelves are being sold, manufactured and used? Well they must be user-friendly which means they should be easy to assemble, carry and modify. They should also be easy to ship, weight aspect and not ungainly. Most importantly it must be worth its price or just cheap, to accomplish this one should keep the amount of material to a minimum whilst the manufacturing must be easy.</p><p>These were some of the questions at issue that this work has started from and they have more or less thoroughly been penetrated.</p><p>In an effort to acquire some answers the possibility to reduce the thickness of the poles to the shelves from 2,5 mm to 2,0 mm, this would present partial solutions to both weight and material issues but before all the price issue though the material contributes to a large piece of the cost. This suggestion appeared when the poles were investigated and calculated from different angels to determine if they would hold out to this kind of change. The angels that were investigated are bending of the pole, the holes in the pole will be sheared (ripped like can opener-effect) by the hooks on the shelf consol and the detachable foot. The result that emerged are that some sizes of the poles can endure the change without any thought whilst the smaller poles requires some further testing and pondering before implementing. The aspect that was found to be norm setting was the bending of the pole.</p><p>The fact that the user friendliness always can be improved a helper was designed. The helper is meant for the user is so he/she easily can see how much merchandise (weight) a shelf and pole can withstand. In other words to make sure that the shelf/pole is not overloaded and risk a breakdown.</p><p>To declare where Itabs system is in regards to its competitor on these important questions a competitor analysis was conducted. The primary test-issues were stability, easy to assemble and if there are any apparent hazardous areas on the stand. Unfortunately there were some difficulties in retrieving the stands from some of the competitors or more importantly the stand from Itab themselves. So a comparison was not possible although they who were interested in testing their stands and had sent them in were to be pleased so a test was conducted. The issue regarding the price was not compared though this report is not meant for the users in the stores.</p>

<p>This thesis project has been written and accomplished in cooperation with HABO AB. The objective of the project was to develop a standard stated packaging system. The background to this is that HABO is not pleased with the system currently in use. The system which HABO is currently using consists of to many sizes. The largest benefit of a standard stated system is that it becomes much easier to organize the packaging with the aid of a computer program. If one manages to standardize the packaging system if will be much easier to calculate how much space that is required for the products in the store. It also enables HABO to sell pre defined product groups.</p><p>The basic condition for the system is that it should be compatible with Hestra wall panels and store equipment. The store equipment proved to be very determining during the project. Due to its design the number of possible variations of sizes decreased considerably.</p><p>Much of the work has been simulated in a computer model which has been constructed in ProEngineer. With aid of the model suitable packaging sizes could be tested on Hestras wall panels.</p><p>The work resulted in a system with three different width sizes (74, 116 and 158 mm), compared to the present five. The number of lengths was set to four (118, 182, 246 and 374 mm) in comparison with today where the length is decided for each product individually. In order for the system to work properly it is crucial the HABOs suppliers can guarantee a specified length for all of the different packaging sizes.</p><p>The basic principle is that both SB-pack and Skin-pack should be possible to combine to achieve the most effective system.</p><p>A couple of improvements were also considered. Standard setting of the width proved to be the hardest challenge. Therefore an alternative could be to use a gliding spear instead of Hestras traditional panel. This allows the spear to be continuously variable. This allows more freedom when it comes to designing the packaging. Regarding different types of packaging SB-pack with long back or colored plastic bag is preferred instead of the traditional SB-pack. The products are displayed in a better fashion and it gives a better impression.</p>

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008. / Title from title screen (site viewed Sept. 16, 2008). PDF text: vi, 91 p. : ill. ; 1 Mb. UMI publication number: AAT 3297751. Includes bibliographical references. Also available in microfilm and microfiche formats.

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<p>Problems of understanding fundamental calculus concepts by students in tertiary education colleges and universities are evidenced by a body of research studies conducted in different parts of the world. The researchers have identified, classified and analysed these problems from historical, epistemological, and learning theory perspectives. History is important because mathematical concepts are a result of the developments of the past. The way knowledge is acquired is an epistemological issue and the major purpose of learning is to acquire knowledge. Hence, these three perspectives qualify to be used as lenses in understanding problems that students encounter in a learning situation. The purpose of this study was to investigate the epistemological obstacles that mathematics students at undergraduate level encounter in coming to understand the limit concept. The role played by language and symbolism in understanding the limit concept was also investigated, because communication in the mathematics classroom takes place by using language and symbols.</p>

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