<p>Volvo Construction Equipment is a world leading company in construction machinery. Tomaintain the best products, development is prioritized. The master thesis regards sound reductionof the hydraulic system on a wheel loader. The background to the master thesis is asimulation made on the hydraulic system, performed autumn 2005. The result of the simulationshows that the energy of the pressure ripple is reduced when the paralleled hydraulicpumps are phase shifted and reduces each others pump pulsations. The aim of the masterthesis is to investigate if the reduction in pulsations also reduces the hydraulic sound.The test has been made on a wheel loader, model L180F, by measuring the pressure pulsationsin the hydraulic system and sound in the drivers cabin. The machine is equipped withtwo nine pistons hydraulic pumps in parallel to the main hydraulic actuators. The measurementshas been made when the sound is highest from the hydraulic system, which is whenthe lifting cylinders has maximum speed. The measurements has been made for differentangels in a range from 0 to 16 degrees phase shift.The result of the master thesis shows that the pulsations in the hydraulic system is reducedbut the sound does not improve with reduced pulsations. The cause to the resultshould be that the pulsations can not be reduced in the entire hydraulic system. The partof the hydraulic system that can not be affected is close to the drivers cabin floor and hastherefor a big contribution to the sound level in the cabin.Volvo is not recommended to introduce the concept because the lack of result in the soundreduction. The result are very dependent of the engine speed, the temperature and the systempressure which make the concept inappropriate for sound and pressure reduction in a wheelloader application. A recommendation is to investigate the possibility of a pulsation attenuatorafter each of the paralleled hydraulic pumps to reduce the pressure ripple in the wholehydraulic system and the hydraulic sound. Another suggestion for investigation is the possibilityto introduce damped attachment points for the hydraulic components to minimizetransmission of vibration to the main structure.</p>

Volvo Construction Equipment is a world leading company in construction machinery. Tomaintain the best products, development is prioritized. The master thesis regards sound reductionof the hydraulic system on a wheel loader. The background to the master thesis is asimulation made on the hydraulic system, performed autumn 2005. The result of the simulationshows that the energy of the pressure ripple is reduced when the paralleled hydraulicpumps are phase shifted and reduces each others pump pulsations. The aim of the masterthesis is to investigate if the reduction in pulsations also reduces the hydraulic sound.The test has been made on a wheel loader, model L180F, by measuring the pressure pulsationsin the hydraulic system and sound in the drivers cabin. The machine is equipped withtwo nine pistons hydraulic pumps in parallel to the main hydraulic actuators. The measurementshas been made when the sound is highest from the hydraulic system, which is whenthe lifting cylinders has maximum speed. The measurements has been made for differentangels in a range from 0 to 16 degrees phase shift.The result of the master thesis shows that the pulsations in the hydraulic system is reducedbut the sound does not improve with reduced pulsations. The cause to the resultshould be that the pulsations can not be reduced in the entire hydraulic system. The partof the hydraulic system that can not be affected is close to the drivers cabin floor and hastherefor a big contribution to the sound level in the cabin.Volvo is not recommended to introduce the concept because the lack of result in the soundreduction. The result are very dependent of the engine speed, the temperature and the systempressure which make the concept inappropriate for sound and pressure reduction in a wheelloader application. A recommendation is to investigate the possibility of a pulsation attenuatorafter each of the paralleled hydraulic pumps to reduce the pressure ripple in the wholehydraulic system and the hydraulic sound. Another suggestion for investigation is the possibilityto introduce damped attachment points for the hydraulic components to minimizetransmission of vibration to the main structure.

Praktiska inslag i fysikundervisning spelar en betydande roll för elevernas lärande. Praktiska undersökande och utforskande arbetssätt gynnar elevernas kunskapsutveckling och deras uppfattning kring nya begrepp. I skolan och särskilt under gymnasiet börjar eleverna gradvis att utveckla och praktisera sitt lärande och använda sin observations- och analysförmåga för att dra slutsatser. Genom vetenskaplig och teknisk utveckling av exempelvis datorsimuleringsteknik har möjligheter att använda animeringar och interaktiva simuleringar uppkommit för att användas i utbildningssammanhang. I detta examensarbete undersöker vi två olika labborativa läraktiviteter inom fysikundervisning. Labborativa läraktiviteter utgörs dels av laboration med traditionell fysisk utrustning, dels av laboration med digitala PhET (Physics Education Technology) datorsimuleringar. Det område inom fysikundervisningen som omfattas i studien är elevernas möjlighet att utveckla konceptuella uppfattningar och förståelse om parallellkopplade elektriska kretsar. I denna fallstudie har vi följt 40 niondeklassare som vi slumpmässigt delat upp i två kontrollgrupper. 20 elever har arbetat med en traditionell laboration med fysiskt lärmaterial i form av olika elektriska kretskomponenter som ska kopplas ihop medan de andra övriga 20 eleverna har arbetat med en laboration med användning av ett digitalt verktyg i form av Circuit Construction Kit: DC-Lab i- PhET-datorsimuleringsmiljön. Undersökningen handlar om att utforska likheter och skillnader i elevernas upplevelser och uppfattningar av begreppet parallellkopplade elektriska kretsar i de två olika labborativa läraktiviteterna, samt att utforska vilka missuppfattningar som kan uppstå hos eleverna efter att ha deltagit i de två olika labborativa läraktiviteterna. Data utgörs av elevernas svar som fritexter till enkätfrågor efter genomförandet av laborationerna, vilket avspeglar elevernas upplevelser och uppfattningar av begreppet parallellkopplade elektriska kretsar i de två olika labborativa läraktiviteterna. I denna fallstudie används en deduktiv tematisk analysmetod för att identifiera likheter och skillnader i elevernas upplevelser och uppfattningar av den parallellkopplade elektriska kretsen under de två laborativa läraktiviteterna, samt att undersöka vilken laborativ läraktivitet som gynnar elevernas uppfattning av den parallellkopplade elektriska kretsen och deras lärande. Teoretiskt ramverk för analysen baseras på en del av Ingerman m.fl. (2007) kategorisystem. Resultatet av vår studie indikerar att en del av eleverna upplevde och tolkade den parallellkopplade elektriska kretsen på olika sätt under de laborativa läraktiviteterna. En del av eleverna som arbetade med traditionell fysisk utrustning missuppfattade hur den parallellkopplade elektriska kretsen fungerade, medan elever som använde CCK-PhET-simuleringsverktyget uppvisade en högre grad av förståelse om den parallellkopplade elektriska kretsen jämfört med elever som använde traditionell fysisk utrustning. Detta visar hur dessa två olika typer av laborationer kan påverka elevernas kunskapsutveckling och lärande. Resultaten av studien skulle kunna ge lärare inblick för att utforma undervisning som främjar elevernas kunskapsutveckling inom fysikundervisning. / Practical elements in physics education play a significant role in students' learning. Hands-on investigative and exploratory methods promote students' experiences and their understanding of various new concepts. In school, and especially during high school, students gradually develop and practice their learning and use their observational skills and analysis to draw conclusions. Through scientific and technological developments, such as computer simulation technology, opportunities arise to use animations and interactive simulations have emerged for use in educational contexts. In this thesis, we investigate two different lab-based learning activities in physics education. Lab-based learning activities consist of traditional physical equipment experimentation and digital PhET (Physics Education Technology) simulation-based experimentation. The area of physics education covered is students' ability to develop conceptual understandings of parall elelectrical circuits. In this case study, we followed 40 ninth-grade students whom we randomly divided into two control groups. Twenty students worked on a traditional laboratory experiment with physical learning materials consisting of different electrical circuit components that needed to be connected, while the other 20 students worked on a digital laboratory experiment using a Circuit Construction Kit: DC-Lab in the PhET simulation environment. The study aims to explore similarities and differences in students' experiences and perceptions of the concept of parallel electrical circuits in the two different lab-based learning activities, as well as to investigate any misconceptions that may arise in students after participating in the two different lab-based learning activities. Data consists of students' responses as free-text answers to survey questions after completing the experiments, reflecting students' experiences and perceptions of the concept of parallel electrical circuits in the two different lab-based learning activities. In this case study, we use a deductive thematic analysis method to identify similarities and differences in students' experiences and perceptions of the parallel electrical circuit during the two lab-based learning activities, as well as to investigate which lab-based learning activity benefits students' understanding of the parallel electrical circuit and their learning. The theoretical framework for analysis is based on a part of Ingerman et al.'s (2007) categorization system. The results of our study indicate that some students experienced and interpreted the parallel electrical circuit differently during the lab-based learning activities. Some students who worked with traditional physical equipment showed misconceptions about how the parallel electrical circuit worked, while students who used the CCK-PhET simulation tool demonstrated a higher level of understanding of the parallel electrical circuit compared to students who used traditional physical equipment. This shows how the two different types of lab-based learning activities can affect students' knowledge development and learning. The results of the study could provide teachers with input to design teaching that promotes students' knowledge development in physics education.