In their challenge-point framework (CPF) Guadagnoli and Lee’s (2004) argue that learning is maximized when a person faces an optimal level of challenge during practice. It is suggested that challenge level can be manipulated through the combination of different practice variables. The purpose of this study was to investigate how practice schedule and self-controlled feedback frequency manipulations affect performance and learning of motor skills. Participants (n=96) attempted to learn three versions of a key-pressing task. The task consisted of pressing five computer keys in specified sequences in a goal criterion time. Participants were assigned to either a blocked practice schedule with self-controlled feedback (BLK-SC), a random practice schedule with self-controlled feedback (RND-SC), a blocked practice schedule with yoked feedback (BLK-YK), a random practice schedule with yoked feedback (RND-YK), a blocked practice schedule and 100 percent feedback (BLK-100), or a random practice schedule with 100 percent feedback (RND-100). Participants in the blocked conditions practiced 30 trials of each task according to a blocked practice schedule. Participants in the random conditions practiced 30 trial of each task according to a random practice schedule. Participants in the self-controlled feedback condition were allowed to choose whether or not to receive feedback on each trial. Yoked participants had their feedback schedule matched to a participant with similar characteristics in the self-control condition. Participants in the 100% feedback condition received feedback after every trial. Participants were also asked to complete the NASA Task Load Index (Hart & Staveland, 1988) and an adapted Perceived Competence for Learning scale (adapted from Williams & Deci, 1996) after the completion of the 5th and 90th trial. After 24 hr participants performed a retention test. The results indicated no difference between groups during retention or for the NASA-TLX and PCL scores. The feedback frequency analysis indicated no differences between BLK-SC and RND-SC groups. In general, the findings of the present study show that the effects of practice schedule conditions can be offset by self-controlled feedback manipulations. They also suggest that a number of different combinations of practice schedules and feedback frequencies can lead to similar challenge levels.

Compared to conventional Steiner tree signal net routing, non-tree topology is often superior in many aspects including timing performance, tolerance to open faults and variations. In nano-scale VLSI designs, interconnect delay is a performance bottleneck and variation effects are increasingly problematic. Therefore the advantages of non-tree topology are particularly appealing for timing critical net routings in nano-scale VLSI designs. We propose Steiner network construction heuristics which can generate either tree or non-tree of signal net with different slack wirelength tradeoffs, and handle both long path and short path constraints. Extensive experiments in different scenarios show that our heuristics usually improve timing slack by hundreds of pico seconds compared to traditional tree approaches while increasing only slightly in wirelength. These results show that our algorithm is a very promising approach for timing critical net routings.

The purpose of this thesis is to derive and analyze the theoretical limits for estimatingthe symboltiming delayof Multiple-Input Multiple-Output (MIMO)systems. Two main N X M system models are considered, where N represents the number of transmit antennas and M denotes the number of receive antennas, the 2 X 2 system used by S.-A. Yangand J. Wu and the 4 X 4system used by Y.-C. Wu and E. Serpedin. The second model has been extended to take into account the symbol time-varying fading. The theoretical estimation limits are shown by several bounds: modified Cramer-Rao bound (MCRB), Cramer-Rao bound (CRB) and Barankin bound (BB). BB will be exploited to obtain accurate information regarding the necessary length of data to obtain good estimation. Two scenarios for synchronization are presented: data-aided (DA) and non-data-aided (NDA). Two models for the fading process are considered: block fading and symbol time-varying fading, respectively, the second case being assumed to be Rayleigh distributed. The asymptotic Cramer-Rao bounds for low signal-to-noise ratio (low-SNR) and for high-SNR are derived and the performance of several estimators is presented. The performance variation of bounds and estimators is studied byvarying different parameters, such as the number of antennas, the length of data taken into consideration during the estimation process, the SNR, the oversampling factor, the power and the Doppler frequency shift of the fading.

“Regional Policy in a Multiregional Setting: When the Poorest are Hurt by Subsidies” Regional subsidies have a positive short-term effect on the recipient regions, but as they alter migration patterns the long-term effects are less clear. This paper demonstrates using a three-region general equilibrium model that subsidising the poorest region may be to its detriment in the long term and thereby increase inter-regional inequality, if the subsidy draws firms from a nearby region that would function better as a production centre. The result has important implications for the design of regional policies, which are often applied simply according to per-capita incomes.  “Learning to Export and the Timing of Entry to Export Markets” Standard trade models are essentially static and do not explain why entry to export markets would be delayed after the instant a firm is formed. This paper proposes a model that endogenously generates the timing of entry to new markets through a learning mechanism. Firms in the model gain experience by entering markets, which eases entry to subsequent markets. The mechanism motivates delays in entry to some markets. More productive firms are less sensitive to the learning effect and thus enter markets sooner and begin by exporting to larger markets. These predictions are confirmed using Swedish firm-level data.  “Airports and the Production of Goods and Services” This paper estimates the effects of airport infrastructure on local employment in certain sectors, using data from the United States. Airport sizes are instrumented for using the 1944 National Airport Plan of the Civil Aeronautics Administration. Airport size is found to have a positive effect on local employment in tradable services, with an elasticity of approximately 0.1, and a negative effect on manufacturing. There is no measurable effect on non-tradable services. The results are relevant to the evaluation of airport improvement projects, which are often carried out using public funds.

The success of the Internet has brought significant changes to the telecommunication industry. One of the remarkable outcomes of this evolution is Voice over IP (VoIP), which enables realtime voice communications over packet switched networks for a lower cost than traditional public switched telephone networks (PSTN). Nevertheless, security and privacy vulnerabilities pose a significant challenge to hindering VoIP from being widely deployed. The main object of this thesis is to define and elaborate unexplored security and privacy risks on standardized VoIP protocols and their implementations as well as to develop suitable countermeasures. Three research questions are addressed to achieve this objective: Question 1:  What are potential unexplored threats in a SIP VoIP network with regard to availability, confidentiality and privacy by means of unwanted traffic and information disclosure? Question 2:  How far are existing security and privacy mechanisms sufficient to counteract these threats and what are their shortcomings? Question 3:  How can new countermeasures be designed for minimizing or preventing the consequences caused by these threats efficiently in practice? Part I of the thesis concentrates on the threats caused by "unwanted traffic", which includes Denial of Service (DoS) attacks and voice spam. They generate unwanted traffic to consume the resources and annoy users. Part II of this thesis explores unauthorized information disclosure in VoIP traffic. Confidential user data such as calling records, identity information, PIN code and data revealing a user's social networks might be disclosed or partially disclosed from VoIP traffic. We studied both threats and countermeasures by conducting experiments or using theoretical assessment. Part II also presents a survey research related to threats and countermeasures for anonymous VoIP communication.

Den här uppsatsen undersöker och analyserar AP-fondernas förvaltning av det svenska pensionskapitalet i relation till dess uppdrag utifrån finansiell teori och tidigare forskning. Halvårsdata och information om fondernas allokering har samlats in från AP-fondernas respektive webbplatser mellan åren 2001 och 2009. Studien har använt ett flertal modeller för att analysera AP-fondernas historiska utveckling. Treynorkvot, Sharpekvot, Informationskvot, Morningstar rating och Jensens alfa har använts för att undersöka fondernas riskjusterade avkastning. Treynor och Mazuys market timing modell har använts för att undersöka huruvida fonderna har förmågan att förutse större marknadsrörelser. Fonderna har utvärderats utifrån tre olika jämförelseindex: ett externt och två interna index. Individer i pensionssystemet får inte välja hur större delen av deras pensionsavsättningar ska förvaltas. Däremot påverkas pensionstagarna i allra högsta grad av hur fonderna utvecklas. AP-fondernas informationsgivning är inte förenlig med dess policy och det påverkar därför vad utomstående kan utvärdera. AP-fonderna har under den valda tidsperioden inte nått målen som är uppsatta för verksamheten. Vidare förefaller det sig som att AP-fonderna är överviktade mot aktier i allmänhet och mot svenska aktier i synnerhet. Det visar sig också att tillgångsallokeringen är den absolut viktigaste faktorn för fondernas utveckling och därmed viktigare än aktiv förvaltning. AP-fonderna uppvisar en positiv riskjusterad avkastning under perioden oberoende vilket mått som används, dock uppvisar inte alla statistisk signifikans. Beroende på vilket jämförelseindex som används skiljer sig resultaten åt. Tredje AP-fonden har dock högst riskjusterad avkastning oavsett vilket jämförelseindex som används. I Morningstar rating får fonderna i genomsnitt två stjärnor av fem möjliga vilket innebär att de presterat under genomsnittet bland internationella pensionsfonder. Argumentet att använda fyra buffertfonder till förvaltning av kapitalet från inkomstpensionen har inte uppfyllts. Studien menar vidare att det finns tecken på stordriftsfördelar och att en eventuell sammanslagning skulle kunna ge en effektivare förvaltning.

The aim of this investigation was to find out how students react to and make use of oral and written feedback given to them in class. Another aim was to find out if they preferred one form over the other and whether they make more use of that form. The investigation was conducted at a Swedish upper secondary school and consisted of a questionnaire survey and interviews with groups of students and with their teachers. The interviews with the students focused on clarifying some of the results from the questionnaire. The teacher interviews gave the teachers a chance to give their version of what they thought worked better and why they chose to work that way.   The results showed that students welcome feedback, especially positive feedback used for encouragement. However, they also thought that there was a higher limit to the amount of feedback they could benefit from. Too much of one sort could be ignored or perceived as discouraging. The feedback mostly used in class was oral feedback. This was also what the students thought they benefited from the most since it invited to discussion about their work. Most of the students thought the feedback should be delivered in private because it could be embarrassing to receive feedback in front of their peers. Nevertheless, feedback on pronunciation and smaller errors that could be of use for their peers as well was acceptable in front of the class.

XMM-Newton is a X-ray telescope launched december 1999, by the European Space Agency, ESA. On board XMM-Newton are two EPIC-MOS X-ray detectors. The detectors are build by Charged Coupled Devices (CCDs), of Metal Oxide Semi-conductor type. The EPIC-MOS cameras have four science operating modes. This project aims to evaluate the calibration for one of these four modes, the timing mode. The evaluation is divided into two parts. The first part is the evaluation of the flux calibration, performed by analysing various observation made in timing mode. The second part is the evaluation of timing properties by performing timing analysis of XMM-Newton observations of the Crab nebula compared to observations made in the radio wavelengths.

<p>Abstract</p><p>DNA replication is an integral part of the cell cycle. Every time a cell divides, the entire genome has to be copied once and only once in a timely manner. In order to accomplish this, DNA replication begins at many points throughout the genome. These start sites are called origins of replication, and they are initiated in a temporal manner throughout S phase. How these origins are selected and regulated is poorly understood. Saccharomyces cerevisiae and Schizosaccharomyces pombe have autonomously replicating sequences (ARS) that can replicate plasmids extrachromosomally and function as origins in the genome. Metazoans, however, have shown no evidence of ARS activity.</p><p>DNA replication is a multistep process with several opportunities for regulation. Potential origins are marked with the origin recognition complex (ORC), a six subunit complex. In S. cerevisiae, ORC binds to the ARS consensus sequence (ACS), but no sequence specificity is seen in S. pombe or in metazoans. Therefore, factors other than sequence play a role in origin selection.</p><p>In G1, the pre-replicative (pre-RC) complex assembles at potential origins. This involves the recruitment of Cdc6 and Cdt1 to ORC, which then recruits MCM2-7 to the origin. In S phase, a subset of these pre-RC marked origins are initiated for replication. These origins are not fired simultaneously; instead, origins are fired in a temporal manner, with some firing early, some firing late, and some not firing at all.</p><p>The temporal firing of origins leads to wide regions of the genome being copied at different times during S phase. , which makes up the replication timing profile of the genome. These regions are not random, and several correlations between replication timing and both transcriptional activity and chromosomal landscape. Regions of the genome with high transcriptional activity tend to replicate earlier in S phase, and it is well know that the gene rich euchromatin replicates earlier than the gene poor heterochromatin. Additionally, areas of the genome with activating chromatin marks also replicate earlier than regions with repressive marks. Though many correlations have been observed, no single mark or transcriptional player has been shown to directly influence replication timing.</p><p>We mapped the replication timing profiles of three cell lines derived from Drosophila melanogaster by pulsing cells with the nucleotide analog bromodeoxyuridine (BrdU), enriching for actively replicating DNA labeled with BrdU, sequencing with high throughput sequencing and mapping the sequences back to the genome. We found that the X chromosome of the male cell lines replicated earlier than the X chromosome in the female cell line or the autosomes. We were then able to compare the replication timing profiles to data sets for chromatin marks acquired through the modENCODE (model organism Encyclopedia Of DNA Elements). We found that the early replicating regions of the male X chromosomes correlates with acetylation of lysine 16 on histone 4 (H4K16).</p><p>Hyperacetylation of H4K16 on the X chromosome in males is a consequence of dosage compensation in D. melanogaster. Like many organisms, D. melanogaster females have two X chromosomes while males have one. To compensate for this difference, males upregulate the genes on the X chromosome two-fold. This upregulation is regulated by the dosage compensation complex (DCC), which is restricted to the X chromosome. This complex includes a histone acetyl transferase, MOF, which acetylates H4K16. This hyperacetylation allows for increased transcription of the X chromosome. </p><p>We hypothesized that the activities of the DCC and the hyperacetylation of H4K16 also influences DNA replication timing. To test this, I knocked down components of the DCC (MSL2 and MOF) using RNAi. Cells were arrested in early S phase with hydroxyurea, released, and pulsed with the nucleotide analog EdU. The cells were arrested in metaphase and labeled for H4K16 acetylation and EdU. We found that male cells were preferentially labeled with EdU on the X chromosome, which corresponded with H4k16 acetylation. When the DCC was knocked down, H4K16 acetylation was lost along with preferential EdU labeling on the X chromosome. These results suggest that the DCC and H4K16 acetylation are necessary for early replication of the X chromosome. Additionally, early origin mapping of different cell lines showed that while ORC density does not differ between male and female cell lines, early origin usage is increased on the X chromosome of males, suggesting that this phenomenon is regulated at the level of activation, not pre-RC formation. Other experiments in female cell lines have been unclear about whether the DCC and subsequent H4K16Ac is sufficient for early X replication. However, these results are exciting because this is, to our knowledge, the first mark that has been found to directly influence replication timing.</p><p>In addition to these timing studies, I attempted to design a new way to map origins. A consequence of unidirectional replication with bidirectional replication fork movement is Okazaki fragments. These are short nascent strands on the lagging strand of replicating DNA. Because these fragments are small, we can isolate them by size and map them back to the genome. Okazaki density could tell us about origin usage and any directional preferences of origins. The process proved to be tedious, and although they mapped back with a higher density around ORC binding sites than randomly sheared DNA, little information about origin usage was garnered from the data. Additionally, the process proved difficult to repeat.</p><p>In these studies, we examined the replication timing program in D. melanogaster. We found that the male X chromosome replicates earlier in S phase, and this early replication is regulated by the DCC. However, it is unclear if the change in chromatin landscape directly influences replication or if the replication program is responding to other dosage compensation cues on the X chromosome. Regardless, we have found one the first conditions in which a mark directly influences the DNA replication timing program.&#8195;</p> / Dissertation

The automotive industry has been in a marathon of advancement over the past decades. This is partly due to global environmental concerns about increasing amount of air pollutants such as NOx (oxides of nitrogen), CO (carbon monoxide) and particulate matters (PM) and decreasing fossil fuel resources. Recently due to stringent emission regulations such as US EPA (Environmental Protection Agency) and CARB (California Air Resource Board), improvement in fuel economy and reduction in the exhaust gas emissions have become the two major challenges for engine manufacturers. To fulfill the requirements of these regulations, the IC engines including gasoline and diesel engines have experienced significant modifications during the past decades. Incorporating the fully flexible valvetrains in production IC engines is one of the several ways to improve the performance of these engines. The ultimate goal of this PhD thesis is to conduct feasibility study on development of a reliable fully flexible hydraulic valvetrain for automotive engines. Camless valvetrains such as electro-hydraulic, electro-mechanical and electro-pneumatic valve actuators have been developed and extensively studied by several engine component manufacturers and researchers. Unlike conventional camshaft driven systems and cam-based variable valve timing (VVT) techniques, these systems offer valve timings and lift control that are fully independent of crankshaft position and engine speed. These systems are key technical enablers for HCCI, 2/4 stroke-switching gasoline and air hybrid technologies, each of which is a high fuel efficiency technology. Although the flexibility of the camless valvetrains is limitless, they are generally more complex and expensive than cam-based systems and require more study on areas of reliability, fail safety, durability, repeatability and robustness. On the contrary, the cam-based variable valve timing systems are more reliable, durable, repeatable and robust but much less flexible and much more complex in design. In this research work, a new hydraulic variable valve actuation system (VVA) is proposed, designed, prototyped and tested. The proposed system consists of a two rotary spool valves each of which actuated either by a combination of engine crankshaft and a phase shifter or by a variable speed servo-motor. The proposed actuation system offers the same level of flexibility as camless valvetrains while its reliability, repeatability and robustness are comparable with cam driven systems. In this system, the engine valve opening and closing events can be advanced or retarded without any constraint as well as the final valve lift. Transition from regenerative braking or air motor mode to conventional mode in air hybrid engines can be easily realized using the proposed valvetrain. The proposed VVA system, as a stand-alone unit, is modeled, designed, prototyped and successfully tested. The mathematical model of the system is verified by the experimental data and used as a numerical test bench for evaluating the performance of the designed control systems. The system test setup is equipped with valve timing and lift controllers and it is tested to measure repeatability, flexibility and control precision of the valve actuation system. For fast and accurate engine valve lift control, a simplified dynamic model of the system (average model) is derived based on the energy and mass conservation principles. A discrete time sliding mode controller is designed based on the system average model and it is implemented and tested on the experimental setup. To improve the energy efficiency and robustness of the proposed valve actuator, the system design parameters are subjected to an optimization using the genetic algorithm method. Finally, an energy recovery system is proposed, designed and tested to reduce the hydraulic valvetrain power consumption. The presented study is only a small portion of the growing research in this area, and it is hoped that the results obtained here will lead to the realization of a more reliable, repeatable, and flexible engine valve system.