Discrete tomography: Magic numbers for NN-fold symmetry

We consider the problem of distinguishing convex subsets of $n$-cyclotomic model sets $\varLambda$ by (discrete parallel) X-rays in prescribed $\varLambda$-directions. In this context, a `magic number' $m_{\varLambda}$ has the property that any two convex subsets of $\varLambda$ can be distinguished by their X-rays in any set of $m_{\varLambda}$ prescribed $\varLambda$-directions. Recent calculations suggest that (with one exception in the case $n=4$) the least possible magic number for $n$-cyclotomic model sets might just be $N+1$, where $N=\operatorname{lcm}(n,2)$.Comment: 5 pages, 2 figures; new computer calculations based on the results of arXiv:1101.4149 and arXiv:1211.6318; presented at ICQ 12 (Cracow, Poland

Maxwell-compensated design of asymmetric gradient waveforms for tensor-valued diffusion encoding

Purpose: Asymmetric gradient waveforms are attractive for diffusion encoding due to their superior efficiency, however, the asymmetry may cause a residual gradient moment at the end of the encoding. Depending on the experiment setup, this residual moment may cause significant signal bias and image artifacts. The purpose of this study was to develop an asymmetric gradient waveform design for tensor-valued diffusion encoding that is not affected by concomitant gradient. Methods: The Maxwell index was proposed as a scalar invariant that captures the effect of concomitant gradients and was constrained in the numerical optimization to 100 (mT/m)$^2$ms to yield Maxwell-compensated waveforms. The efficacy of this design was tested in an oil phantom, and in a healthy human brain. For reference, waveforms from literature were included in the analysis. Simulations were performed to investigate if the design was valid for a wide range of experiments and if it could predict the signal bias. Results: Maxwell-compensated waveforms showed no signal bias in oil or in the brain. By contrast, several waveforms from literature showed gross signal bias. In the brain, the bias was large enough to markedly affect both signal and parameter maps, and the bias could be accurately predicted by theory. Conclusion: Constraining the Maxwell index in the optimization of asymmetric gradient waveforms yields efficient tensor-valued encoding with concomitant gradients that have a negligible effect on the signal. This waveform design is especially relevant in combination with strong gradients, long encoding times, thick slices, simultaneous multi-slice acquisition and large/oblique FOVs

The impact of horizontal projections on external fire spread - A numerical comparative study

The aim of the report was to investigate and compare the effect of horizontal projections along with different spandrel heights between the unprotected openings in the building facade. The effect was more specifically the effect on the risk level in regards to the external vertical fire spread. Furthermore, based upon the performance requirements of the Swedish building regulations (BBR), the aim was to compare the effects of the different protection methods. From the validation study it was shown that FDS version 6.2.0 is well suited as calculation tool for the problem area given the presented settings. The main conclusions drawn from the report was that the use of at least a 60 cm deep horizontal projection results in lesser consequences and lower risk levels at the facade above the projection compared with the scenarios built up by different spandrel heights. Also, the conclusion was that the use of at least a 60 cm deep horizontal projection results in lower risk levels above the projection compared with the risk level accepted in the prescriptive part of the BBR. The opposite was seen for the 20 cm and 30 cm deep horizontal projections. The use of 60, 80 and 100 cm deep horizontal projections resulted in 15-50 % reduction in the relative exposure of adiabatic surface temperature at the facade 1.2 m above the underlying opening. The main horizontal projections used in the report were 20 cm thick rectangular non-combustible balconies with open sides and no separation walls, extending 0.4 m on each side of the underlying openings. Based on the findings in this report, a spandrel distance of at least 1.2 m in the building exterior as stated by the BBR can be replaced by at least a 60 cm deep horizontal projection positioned at any height above the underlying opening. However, additional simulations on other setups are needed to determine the general use of this outcome. Furthermore, recommendations were given on the design of BBR for the problem area.Balkongplattor som alternativ till bröstning i byggnadsfasaden Tidigare forskning har visat att brandspridning i bostadshus ofta sker vertikalt via fönster i byggnadsfasaden. Samtidigt visar sig nivån på brandskyddet mot detta skilja sig åt mellan olika länders byggnadsregler. Att det finns oenighet i frågan antyder att ytterligare forskning behövs inom ämnet. I avsnitt 5:553 av de svenska byggreglerna (BBR 22) anges kraven för fönster i yttervägg. Fönster placerade ovanför varandra i höjdled mellan skilda brandceller i samma byggnad ska utformas så att brandspridning mellan brandcellerna begränsas. Enligt de förenklade reglerna uppfylls detta om avståndet mellan fönstren är minst 1,2 m. Om avståndet är mindre än 1,2 m måste antingen ett av fönstren vara brandklassad i klass E 30 eller båda i klass E 15. Därutöver får de brandklassade fönstren endast vara öppningsbara med verktyg, nyckel eller liknande. Utformningen av BBR i frågan skapar problem eftersom dagens byggnader ofta innehåller stora glaspartier längs med byggnadsfasaden för att skapa större ljusinsläpp. Även fasadutformningar som franska balkonger med öppningsbara dörrsektioner innebär potentiella problem. Problemet är mer specifikt att utformningarna av dessa glaspartier kan täcka stora delar av fasaden i höjdled, vilket innebär att bröstningskravet på 1,2 m hotas vid normal bjälklagshöjd. För en fransk balkong innebär detta att de endast får öppnas med nyckel, alternativt ska utrustas med dörrstängare, vilket sällan är önskvärt med en fransk balkong. Ett sätt att lösa problemet med reducerad bröstning som ett resultat av nya fasadutformningar vore att anlägga en balkongplatta med lämplig utformning mellan fönstren i fasaden. Plattan skulle avleda flammorna bort från byggnadsfasaden, vilket således hade reducerat brandpåverkan på den ovanliggande fasaden och därigenom hämmat den vertikala brandspridningen. Tillämpningen av balkongplattor hade kunnat fungera som ett alternativ till de förenklade reglerna, vilket hade kunnat leda till samma risknivåer gällande den vertikala brandspridningen för positioner på fasaden ovanför balkongplattan jämfört med positioner längs med bröstningshöjden på 1,2 m. I ”Balkongplattors påverkan på extern brandspridning - En numerisk jämförande studie” undersöks och jämförs effekten av balkongplattor och olika bröstningshöjder mellan icke brandklassade fönster i byggnadsfasaden. Mer specifikt undersöks påverkan på risknivån med hänsyn till den externa vertikala brandspridningen. Vidare jämförs denna påverkan mellan de olika skyddsmetoderna med de förenklade reglerna i de svenska byggreglerna (BBR) som grund. För att ta reda på ovanstående används programmet FDS version 6.2.0 som beräkningsverktyg. För att kunna bedöma rimligheten i beräkningarna och i allmänhet utvärdera programmet för problemområdet, har en valideringsstudie utförts. Beräkningar i FDS valideras mot data från ett storskaligt brandförsök på en modifierad SP Fire 105 test rigg, vars geometri är nära knuten till problemområdet. Den generella slutsatsen är att FDS väl uppskattar gas- och yttemperaturer såväl som infallande strålning. För att uppnå likvärdigt resultat nära branden krävs emellertid en fin mesh-upplösning, närmare bestämt ett D^*/δx av åtminstone 30. Ur valideringsstudien framgår det att FDS version 6.2.0 är väl lämpad som beräkningsverktyg för problemområdet givet de presenterade inställningarna i studien. Resultaten från valideringsstudien tas i beaktning under beräkningarna i den jämförande analysen. I den jämförande analysen uppskattas med hjälp av FDS konsekvensen på den ovanliggande fasaden från en brand i en underliggande lägenhet. Konsekvensen beskrivs av den adiabatiska yttemperaturen samt FDS-variabeln incident heat flux och åskådliggörs i olika diagram med konsekvensen som en funktion av höjden ovanför den underliggande öppningen. I dessa diagram jämförs sedan konsekvenserna från scenarier med olika djupa balkongplattor i fasaden mot scenarier med olika bröstningshöjder mellan öppningarna. Genom att låta konsekvenserna från bröstningsfallet utgöra den representerade risknivån kan ändringen i risknivå studeras i diagrammen efter införandet av olika balkongplattor. Därefter kan slutsatser dras om huruvida risknivån stiger eller sjunker efter införandet av dessa balkongplattor jämfört med olika bröstningshöjder samt bröstningskravet enligt BBR. Den generella slutsatsen är att användningen av åtminstone en 60 cm djup balkongplatta resulterar i mindre konsekvenser och lägre risknivåer ovanför plattan jämfört med scenarier uppbyggda av olika bröstningshöjder. Det motsatta ses för de 20 cm och 30 cm djupa balkongplattorna. Den generella slutsatsen är även att användningen av åtminstone en 60 cm djup balkongplatta resulterar i lägre risknivåer ovanför plattan jämfört med den risknivå som är accepterad i de allmänna råden i BBR. Det motsatta ses även här för de 20 cm och 30 cm djupa balkongplattorna. Användningen av 60, 80 och 100 cm djupa balkongplattor resulterar i 15-50 % reduktion av den relativa exponeringen av adiabatisk yttemperatur på fasaden, 1,2 m ovanför den underliggande öppningen. De huvudsakligen använda balkongplattorna i rapporten är 20 cm tjocka, rektangulära och icke-brännbara balkonger med öppna sidor samt inga skiljeväggar, utstickande 0,4 m åt var sida om den underliggande öppningen. Två typer av öppningar i den obrännbara fasaden studeras: en 0,8 m (B) * 2 m (H) dörr och ett 1,2 m (B) * 1,2 m (H) fönster. I några av scenarierna placeras balkongplattorna precis ovanför den underliggande öppningen. Givet förutsättningarna i studien kan därmed en bröstning av 1,2 m som anges i de svenska byggreglerna ersättas med åtminstone en 60 cm djup balkongplatta placerad på en valfri höjd ovanför den underliggande öppningen. Dock behövs ytterligare simuleringar med andra uppställningar för att fastställa resultatets allmänna tillämpning. En rekommendation till de svenska byggreglerna vore att vidare utreda möjligheterna till att använda balkongplattor som skydd, enligt ovan, för att sedan utveckla de allmänna råden likt utformningen av de Nya Zeeländska byggnadsreglerna. Detta är fördelaktigt eftersom de senare reglerna erbjuder antingen valet av en eller kombinationer av de skyddsmetoder som testas i rapporten. Detta skulle medföra att flexibla skyddsmetoder erbjuds i BBR som fortfarande resulterar i samma risknivåer jämfört med dagens bröstningskrav på 1,2 m, samt att likadana risknivåer skulle kunna förväntas i olika byggnader även vid tillämpande av balkonger som ersättning för bröstningen

NMR Diffusion Studies of Association in Surfactant Systems Inclusion Complexes, Micellar Solutions and Microemulsions

The aim of this thesis has been to investigate self-diffusion behavior of host-guest complex, microemulsion and polymer solution. Pulsed Field Gradient NMR (PFG-NMR) was shown to provide detailed molecular information in all system studied. The general strategy was to measyre the diffusivities of the species and from there get molecular insight into the aggregation and dynamics of the system. Guest host interaction has been studied between β-cyclodextrin (β-CD) and different cationic surfactant. The equilibrium constant (K11) increases as a function of the number of CH2 groups in the surfactant chain. It could be concluded that the cavity of β-CD could incorporate approximately 10-12 CH2 groups and that it is the hydrophobic interaction that mainly is responsible for the inclusion complex formed. The interaction between the gemini surfactant and β-CD formed a 2:1 (CD:gemini) complex in a two step mechanism with the first association constant higher than the second one (K2:1), but both relatively small in comparison with the analogue singled tailed surfactant. The values of the K11 and K21 increased with gemini spacer length which indicate that the available space on the gemini molecule is important. The second association constant shows no cooperatively and its magnitude are discussed in terms of steric constrains. Bolaform surfactant complexation was investigated with both β-CD and α-CD with Isothermal Titration Calorimetry (ITC). The K11, enthalpy and entropy of formation were obtained. From ITC a molecular interpretation is made explaining the enthalpy and entropy difference between α- and β-CD. In a second study diblock copolymers of the type methoxy poly(ethylene oxide)- poly(alkylene oxide) were incorporated into the nonionic bicontinuous microemulsion at 298 K. An enhancement of the microemulsion in solubilising water and oil were observed with a boosting factor of 9. The self-diffusion coefficients of the components in the system were measured and provided molecular information on how the microstructure of the bicontinuous microemulsion changed upon addition of the polymers. The diffusion study concerning the aqueous solution of the synthetic polymers, PEO- PPO-PEO, is focused towards analyzing the PFG-NMR decay correctly. The polydispersity has consequences on the polymer self-assembly, which were highlighted, modeled and discussed based on PFG-NMR data. The main conclusion is that the curved NMR decay as obtained for self-assembly can be explained with a multi-component ideal solution

Technological Competencies and Firm Performance: Analyzing the Importance of Internal and External Competencies

In this paper, we analyze the relationship between technological competencies (TC) and firm performance. Theoretically, the importance of TC is well established and widely accepted. Therefore, it is surprising that a number of empirical studies have been unable to confirm a substantial positive relationship between TC and firm performance. We identify two major reasons for this: [i] affected by the availability and choice of indicators existing studies are often biased towards large firms; and [ii] they frequently do not consider both internal and potential access to firm-external TC. This paper discusses conceptually the interplay between firm-internal and firm-external TC as well as the mediating effect of firm size. These relationships are then analyzed empirically using Swedish micro data on 15,682 firms in 290 Swedish municipalities. Novel indicators based on occupational statistics are combined with measures of time-distance accessibility to study internal and external TC. The results provide evidence for a positive relationship between firm growth and TC. In particular, the combination of firm-internal and firm-external competencies seems to be conducive for growth. Lastly, our study suggests that firm size is an important factor to further our understanding about these relationships. Based on this we identify a number of future research questions to be addressed

The decay and rise of a new strategy: A case study of the Effect of Financial Crisis on a company´s strategy

Problem: More information is needed on how a company can overcome hardship during stormy business cycles. Appropriate management strategies on how to get the business going as the dust settles is essential in order for a company to sustain on the market. Management in any recession is difficult, especially in today´s turmoil. Nonetheless, corporate strategic renewal is needed to mitigate the risk of default and optimize management of the company. The question is what should the company do in order to keep the resilience up? Purpose: To explain the factors of corporate renewal that will affect the strategy in a positive way, from a theoretical and empirical point of view. This is done by identifying the factors affecting a company´s strategy during the process of renewing the strategy. Methodology: This thesis utilizes the abductive research method with a positivistic philosophical approach. Conclusion: The factors; uncertainty, leadership, change, adaption and information, are essential while renewing a strategy during a company´s crisis

Studies Into the Use of Non-linear Ultrasound to Detect Corroded Steel Plates Embedded in Concrete

In some nuclear power plants, the containment liners are embedded in concrete. The purpose of the containment liner is to minimize the risk of radioactive leakage by granting a leak-tight containment building. In the presence of flaws in the surrounding concrete, such as voids, or foreign objects embedded in the concrete, there is a risk that the liner plate might corrode. This could degrade the leak tightness of the containment building, leading to an increased risk of radioactive leakage. A project is being carried out at Lund University whose purpose is to assess the capability of non-linear ultrasound to detect corroded steel plates embedded in concrete. Second harmonic analysis has been used to determine if general corrosion induced an increase in acoustical non-linearity. This was done by inspecting a steel plate with varying grades of corrosion immersed in water. Results from this study indicated that severe corrosion increases the relative parameter of quadratic non-linearity ( Beta’). Beta' is given by the ratio between the second harmonic amplitude and the fundamental amplitudesquared. Building on this result, initial findings from modulation experiments on concrete cylinders with embedded steel plates with varying grades of corrosion are presented

Diffusional exchange versus microscopic kurtosis from CTI: two conflicting interpretations of the same data

Correlation tensor imaging (CTI) is a new diffusion MRI framework that utilises double diffusion encoding (DDE) to resolve isotropic, anisotropic and microscopic kurtosis sources. Microscopic kurtosis in CTI is provided by the contrast between SDE and parallel DDE signals at the same b-value. Multi-Gaussian exchange (MGE) is a diffusion MRI framework that utilises DDE to measure exchange. The highest exchange sensitivity in MGE is obtained by contrasting SDE and DDE signals at the same b-value. CTI and MGE can thus be applied to analyse the same data but provide conflicting interpretations of that data. We perform Monte Carlo simulations in different geometries with varying levels of exchange to determine which approach is more compatible with the data. Simulations reveal that in all microstructures considered, CTI microscopic kurtosis drastically increases when exchange is introduced. Furthermore, in microstructures that are well-described by the multi-Gaussian assumption, CTI-estimated microscopic kurtosis increases with both the exchange rate and the mixing time, despite fulfilment of the long-mixing-time condition of CTI. Increasing the exchange rate by a factor of 2 positively biases CTI microscopic kurtosis by approximately the same factor. At a modest exchange rate of 10 /s, varying the mixing time from 12 to 100 ms increases CTI microscopic kurtosis by at least a factor of 3. To address this problem, we propose a heuristic approach to combine CTI and MGE to estimate intra-compartmental kurtosis unconfounded by exchange and demonstrate its feasibility using numerical simulations

Collaboration for Innovation - a study in the Öresund Region

We have made a thesis about Collaboration for Innovation in the Öresund region from a Swedish perspective. The thesis is taking both regional and corporate aspects into consideration when studying this subject. The empiric material is based upon several interviews with persons having knowledge about our subject as well as a web survey including 49 companies situated in the Öresund region. We have been able to divide our findings into two kinds of problems: Structure- and Process problems. The analyze is partialy based upon the Triple- and Penta-Helix models