To make progress in the face of failures, long-running parallel applications need to save their state, known as a checkpoint. Unfortunately, current checkpointing techniques are becoming untenable on large-scale supercomputers. Many applications checkpoint all processes simultaneously--a technique that is easy to implement but often saturates the network and file system, causing a significant increase in checkpoint overhead. This thesis introduces compiler-assisted staggered checkpointing, where processes checkpoint at different places in the application text, thereby reducing contention for the network and file system. This checkpointing technique is algorithmically challenging since the number of possible solutions is enormous and the number of desirable solutions is small, but we have developed a compiler algorithm that both places staggered checkpoints in an application and ensures that the solution is desirable. This algorithm successfully places staggered checkpoints in parallel applications configured to use tens of thousands of processes. For our benchmarks, this algorithm successfully finds and places useful recovery lines that are up to 37% faster for all configurations than recovery lines where all processes write their data at approximately the same time. We also analyze the success of staggered checkpointing by investigating sets of application and system characteristics for which it reduces network and file system contention. We find that for many configurations, staggered checkpointing reduces both checkpointing time and overall execution time. To perform these analyses, we develop an event-driven simulator for large-scale systems that estimates the behavior of the network, global file system, and local hardware using predictive models. Our simulator allows us to accurately study applications that have thousands of processes; it on average predicts execution times as 83% of their measured value. / text

Η παρούσα διπλωματική εργασία έχει ως σκοπό την ανάπτυξη εφαρμογής σε iPhone για την προσομοίωση κβαντικών υπολογισμών. Για την υλοποίηση του γραφικού περιβάλλοντος της εφαρμογής αντί για τη native γλώσσα προγραμματισμού για iphone (objective c), καθώς και τα επίσημα εργαλεία της apple επιλέχθηκε η πλατφόρμα phonegap. Αρχικά μελετήθηκαν: πρώτον, οι βασικές έννοιες που διέπουν τους κβαντικούς υπολογιστές και δεύτερον, η χρήση και οι δυνατότητες των διάφορων προγραμματιστικών γλωσσών και εργαλείων. Στη συνέχεια δημιουργήθηκε η γραφική διεπαφή της εφαρμογής με το χρήστη και εν τέλει αναπτύχθηκε η βιβλιοθήκη η οποία εκτελεί τους κβαντικούς υπολογισμούς. / This diploma dissertation presents the development of an iPhone application that simulates the quantum calculation. Instead of using the native programming language for iPhone applications, Objective C, web technologies an PhoneGap where chosen. At first, the theory of quantum calculation was studied. Then the technologies available for developing mobile apps where studied and therefore PhoneGap and web technologies were chosen. Finally the app was developed in two parts, firstly the user interface and finally the library that executes the quantum calculation.

För att bibehålla och öka produktiviteten i skogsbruket behövs nya tekniker och arbetsmetoder. Syftet med detta examensarbete var att, för sektionsgallring med flerträdshantering, ta fram ett fungerande simulatorkoncept genom att utforma ett testbestånd i simulatormiljö. Vidare var syftet att studera maskinförares inlärningsförmåga och upplevelse av simulatormiljön, samt utvärdera möjligheten att använda en simulator vid forskning och tidsstudier. Studien genomfördes genom tidsstudier av fyra maskinförares körningar i en skogsmaskinsimulator och genom en enkät.  Beståndet blev ett väl fungerande arbetsområde med bra stamantal med god översikt där testerna kunde genomföras. Maskinens funktion var mycket snarlika verkliga förhållanden. Testkörningarna visade att inlärningsperioden måste beaktas vid tidsstudier i simulator. Studien indikerar på att det finns goda möjligheter att använda simulator vid inlärning av arbetsmetoder. Flerträdsutrustning och bra arbetsmetoder ger förarna en förbättrad arbetsmiljö vilket leder till en förbättrad produktivitet.

In this project, the perception of distance and the degree of immersion in a game, with two different visualisation techniques, have been evaluated. A bicycle simulator was used, and the game has been tested in a non-immersive virtual reality, by projecting the game on a screen, and using an immersive virtual reality by Oculus Rift. The study provides a preliminary investigation that focuses on how humans can perceive the distance, an overview of the term immersion and how to quantify this component.Regarding the study of the perception of distance, to subjects who have tested the game has been asked their perceptions of distance with respect to a given object. The immersion was studied and evaluated using a questionnaire given to each subject.The results showed an underestimation of distance in both the visualisation of the game, precisely a greater underestimation respect to real distance when the screen was used was found.The degree of immersion did not detect large differences between the two visualisation techniques.

The tribology of a wide range of designs of compliant layer acetabular cups has been evaluated using a simulator. The simulator applied a dynamic load of 2 kN and a sinusoidal motion of ±25 , and measured the frictional resistance directly. In general the friction developed in these joints was extremely low, with friction factors typically below 0.01. When the experimental results were compared with theoretical estimates of friction a poor correlation was found. Further analysis suggested that the design of compliant layer acetabular cups was insensitive to many of the parameters suggested by theory. In particular, the radial clearance and femoral head size were not found to be critical. In addition, methods were proposed and their effectiveness demonstrated to measure friction at the on-set of motion (start-up friction), and the steady state friction in realistic compliant layer knees. The adhesion between compliant layers and a rigid backing have been investigated, with the aim of developing a good bond between them. The peel test was used to demonstrate an excellent diffusion bond between a low modulus medical grade polyurethane, and a similar high modulus grade of polyurethane. The processing conditions used to manufacture the test piece were optimised to maximise the bond strength. The bond was found to be stable after immersion in Ringers solution at 37 C for 52 weeks, and after acetabular cups were subjected to 14 million 4 kN loading cycles. A six station knee wear simulator was designed and commissioned. The simulator applied a dynamic load and an anterior-posterior translation individually to each station, as well as a flexion-extension motion common to all six stations. The simulator was computer controlled entirely using servo hydraulics. Wear rates were obtained from tests lasting up to 8 million cycles conducted on UHMWPE joints.

In a natural gas field, determining the life of the field and deciding the best production technique, meeting the economical considerations is the most important criterion. In this study, a field in Thrace Basin was chosen. Available reservoir data was compiled to figure out the characteristics of the field. The data, then, formatted to be used in the commercial simulator, IMEX, a subprogram of CMG (Computer Modeling Group). The data derived from the reservoir data, used to perform a history match between the field production data and the results of the simulator for a 3 year period between May 2002 and January 2005. After obtaining satisfactory history matching, it was used as a base for future scenarios. Four new scenarios were designed and run to predict future production of the field. Two new wells were defined for the scenarios after determining the best region in history matching. Scenario 1 continues production with existing wells, Scenario 2 includes a new well called W6, Scenario 3 includes another new well, W7 and Scenario 4 includes both new defined wells, W6 and W7. All the scenarios were allowed to continue until 2010 unless the wellhead pressure drops to 500 psi. None of the existing wells reached 2010 but newly defined wells achieved to be on production in 2010. After comparing all scenarios, Scenario 4, production with two new defined wells, W6 and W7, was found to give best performance until 2010. During the scenario 4, between January 2005 and January 2010, 7,632 MMscf gas was produced. The total gas production is 372 MMscf more than Scenario 2, the second best scenario which has a total production of 7,311MMscf. Scenario 3 had 7,260 MMscf and Scenario 1 had 6,821 MMscf respectively. A nodal system analysis is performed in order to see whether the initial flow rates of the wells are close to the optimum flow rates of the wells, Well 1 is found to have 6.9 MMscf/d optimum production rate. W2 has 3.2 MMscf/d, W3 has 8.3 MMscf/d, W4 has 4.8 MMscf/d and W5 has 0.95 MMscf/d optimum production rates respectively.

Mannheim, Univ., Diss., 2003.

Thesis (M.S.)--University of Iowa, 2006. / Supervisor: Lea-Der Chen. Includes bibliographical references (leaves 114-116).

Techn. University, Diss., 2005--Darmstadt.

This thesis revolves around how to verify that the new aircraft simulator that is currently under development at Saab Aeronautics functions as intended. Because the system is still under development, the assignment is about developing various suggestions on how to verify that the new simulator is working properly. After various test proposals have been developed for the system, I will put them to the test with the help of National Instruments software. I will also make a world study to compare how other companies develop their simulators.