Fire Dynamics in Multi-Room Compartment Fires

Fire dynamics in multi-room compartments are explored in this thesis and new methods to study conditions in rooms adjacent to the room of fire origin are presented. Simple and transparent engineering methods can create good possibilities for understanding different complex phenomena present in fire science. Such methods can also be used in the design process in order to perform rough estimates before more advanced and time-consuming analyses are performed. There are several methods available for studying conditions in the room of fire origin. However, there are few methods that can be used to study the conditions in adjacent spaces. This means that there is a need for developing new fire engineering methods for such spaces. In this thesis two such methods are presented and evaluated. A fire in a single room is complex and the problem increases in complexity when multiple rooms are studied. It can therefore be hard to control all influencing variables and to reproduce fire experiments in multi-room compartments. As a part of the exploration of multi-room compartment fires in this thesis, the reproducibility of a full-scale scenario in a typical apartment building is studied. The temperature varied between ±10-35% around the average temperature depending on scenario, location and time after ignition. An alternative to performing traditional experiments is to use numerical experiments. Numerical experimentation is considered to be a promising research method in fire science, and it is evaluated as a part of this thesis

Evaluation of a multi-zone modelling concept for large volume buildings and tunnels

The multi-zone modelling concept could be a good alternative to two-zone modelling and CFD modelling for some situations when performing fire safety designs. However, few such models exist, and the evaluation of the concept is scarce. This paper is dedicated to study the multi-zone modelling concept and its usefulness in fire safety engineering by benchmarking it against experimental data and simulations with FDS. Two different areas are studied in the paper: large volume buildings and tunnel fires.The simulations of the large volume buildings results in reasonable estimates of gas temperatures and it is also concluded that the multi-zone concept can be a complement to more advanced numerical modelling tools like FDS. The results from the tunnel scenarios are promising but it is concluded that more benchmarking is needed

Numerical experiments and compartment fires

Fires are complex and it is hard to derive relationships from theory in fire science. Full-scale and small-scale experiments have been used with great success in order to increase the understanding of fire chemistry and fire dynamics. An alternative or complement to these often expensive and resource demanding traditional experiments are numerical experiments. In this paper, numerical experiments are reviewed as a research method and put into the context of traditional compartment fire experiments. Benefits and challenges with numerical experiments compared to traditional compartment fire experiments are presented and discussed in this paper. Numerical experiments are a promising method in fire science research. However, it is currently not considered satisfying to solely use a numerical experiment to study a certain fire phenomena. Different experimental methods should not be regarded as competitive but as complementary, and a combination of traditional and numerical experimental methods are in many cases appropriate in order to analysis a certain fire phenomena

A Survey on Graph Kernels

Graph kernels have become an established and widely-used technique for solving classification tasks on graphs. This survey gives a comprehensive overview of techniques for kernel-based graph classification developed in the past 15 years. We describe and categorize graph kernels based on properties inherent to their design, such as the nature of their extracted graph features, their method of computation and their applicability to problems in practice. In an extensive experimental evaluation, we study the classification accuracy of a large suite of graph kernels on established benchmarks as well as new datasets. We compare the performance of popular kernels with several baseline methods and study the effect of applying a Gaussian RBF kernel to the metric induced by a graph kernel. In doing so, we find that simple baselines become competitive after this transformation on some datasets. Moreover, we study the extent to which existing graph kernels agree in their predictions (and prediction errors) and obtain a data-driven categorization of kernels as result. Finally, based on our experimental results, we derive a practitioner's guide to kernel-based graph classification

Restrictions on infinite sequences of type IIB vacua

Ashok and Douglas have shown that infinite sequences of type IIB flux vacua with imaginary self-dual flux can only occur in so-called D-limits, corresponding to singular points in complex structure moduli space. In this work we refine this no-go result by demonstrating that there are no infinite sequences accumulating to the large complex structure point of a certain class of one-parameter Calabi-Yau manifolds. We perform a similar analysis for conifold points and for the decoupling limit, obtaining identical results. Furthermore, we establish the absence of infinite sequences in a D-limit corresponding to the large complex structure limit of a two-parameter Calabi-Yau. In particular, our results demonstrate analytically that the series of vacua recently discovered by Ahlqvist et al., seemingly accumulating to the large complex structure point, are finite. We perform a numerical study of these series close to the large complex structure point using appropriate approximations for the period functions. This analysis reveals that the series bounce out from the large complex structure point, and that the flux eventually ceases to be imaginary self-dual. Finally, we study D-limits for F-theory compactifications on K3\times K3 for which the finiteness of supersymmetric vacua is already established. We do find infinite sequences of flux vacua which are, however, identified by automorphisms of K3.Comment: 35 pages. v2. Typos corrected, ref. added. Matches published versio

Den svenska tillväxtskolan

Den svenska tillväxtskolan, som här för första gången ges en samlad presentation, är en unik svensk nationalekonomisk skolbildning, med Erik Dahmén som den mest kände företrädaren. Denna tradition betonar att ekonomisk tillväxt är en evolutionär process där entreprenörskap och innovationer spelar en central roll. Ekonomisk utveckling sker inom ramen för breda utvecklings- och kompetensblock, där det nya utmanar det gamla i en process av kreativ förstörelse. I uppsatsen presenteras de bärande idéerna inom denna skolbildning. Dessutom relateras kortfattat den svenska tillväxtskolans synsätt till traditionell nationalekonomi.The Swedish Growth School; Erik Dahmén; Development Blocks; Competence Blocs; The Experimentally Organized Economy; Institutional Blocs

Dödsbränder i bostäder 2012-2015 : En studie av fastighetsinformation

The purpose of this work is to study fatal residential fires and see if they are correlated with any specific building characteristics. In this report, data on fatal fires are paired with data about the properties where the fires occurred. The analysis has shown that apartment buildings are overrepresented among properties with fatal fires compared to single-family units and agricultural units. It also shows that more fatal fires occur in rented apartments than condominiums. Moreover, it appears that some construction periods are over-represented in fatal fires. It can thus be seen that there are differences in the number of fatal fires in terms of various building characteristics. However, it is doubtful whether it is the building characteristics that explain this, or if there is other underlying factors, e.g. socioeconomic factors. It may in any case be important to know what building characteristics that is over-represented in fatal fires when working with or deciding on different preventative strategies

Help sowing of grassland : renovate existing grassland or establish a new?

Arbetet är en litteraturstudie där jag har undersökt hur vallen påverkas av hjälpsådd och vilka faktorer som är mest avgörande i ett system med långliggande vallar. Arbetet innefattar inte några egna försök däremot har jag granskat andras försök både i Sverige och internationellt. En stor kostnad uppkommer i samband med att vallen ska anläggas. Denna kostnad ska sedan fördelas på vallens totala liggtid som ofta är ca tre år vid intensiv vallodling. Vallens avkastning minskar i regel med ökad ålder och en metod för att öka avkastningen skulle kunna vara att årligen hjälpså med en mindre mängd vallfrö. Vallens liggtid skulle på så vis kunna förlängas och den dyra anläggningskostnaden spridas på fler år. Det som talar mot hjälpsådd är att det är en förhållandevis ny teknik i Sverige. Det är viktigt att respektive vallfröart hamnar på rätt sådjup om etableringen ska lyckas. Om optimala förutsättningar råder kan mängden vallfrö halveras utan att avkastningen påverkas. Om vallen sås i rader eller bredsprids har ingen betydelse. Kemisk bekämpning under insåningsåret har negativ påverkan på klövern och ger ingen merskörd hos vallen. Valet av skyddsgröda har ingen betydelse så länge insådden får tillräckligt med ljus. Vallen gynnas av att skyddsgrödan tas som helsäd. Vad som är optimal vallålder beror på vilken vallart som är mest dominerande i blandningen. Många högavkastande arter tappar snabbt i avkastning efter de två första åren och i ett system med extensiva långliggande vallar bör man redan från början tänka igenom vilka arter som är mest lämpliga. Hjälpsådd kan ske med befintlig såmaskin. Både släp- och skivbillar fungerar. En vanlig vält utrustad med frölåda går också bra. Det finns även ogräsharvar utrustade med frölåda och speciella direktsåmaskiner. Granskningen av försöksresultaten ger olika svar. Fem av försöken visar att hjälpsådd ökar avkastningen medan två försök visar att metoden inte fungerar. De försök som visar att hjälpsådd inte ökar vallens avkastning är utförda i Sverige. Två försök utförda på Irland, ett försök på Nya Zealand, och två försök i Sverige visar alla på ökad avkastning med hjälpsådd. Flera av försöken är dock inte trovärdiga eftersom material och metod är otydligt formulerade eller så har försöken utförts under en för kort tidsperiod. Vad som också är värt att nämnas är att flera av försöken är närmare 20 år gamla och mer moderna studier av ämnet behövs om man vill hävda att hjälpsådd faktiskt fungerar. Ett av de svenska försöken som visar att hjälpsådd inte ökar vallens avkastning kan ses som mycket trovärdigt. Anledningen till detta är att försökets upplägg finns noga dokumenterat och att man mätt både avkastning, näringsinnehåll och botanisk sammansättning under flera år. Detta utan att några signifikanta skillnader mellan försöksrutorna eller försöksplatserna kunnat fastslås. Mina slutsatser blir därför att hjälpsådd sannolikt inte kan användas för att motverka den minskade avkastningen i högavkastande vallar, i alla fall inte under svenska förhållanden. Detta beror förmodligen på att de nya plantorna blir utkonkurrerade av den befintliga vallen. Det är dock troligen möjligt att hjälpsådd på gamla mycket lågavkastande vallar skulle kunna höja avkastningen, eftersom det i extrema situationer alltid finns en lägsta nivå då alla efterkommande åtgärder förbättrar resultatet.The work is a literature review in which I have examined how the yield of grass is affected by the influence of help seeding and which factors are the most crucial in a system with permanent grassland. This work does not include any own experiments, however, I have examined other trials both in Sweden and abroad. A major cost occurs in the construction of the grassland. This cost will then be distributed on the pastures total time, often about three years in an intensive system. The grass yield usually decreases with age and a method to reduce the yield could be annual help seeding with a minor amount of grass seed. The pastures lying time would thereby be extended and the expensive construction cost could be spread on more years. What speaks against help seeding is that it’s a relatively new method in Sweden. It is important that each seed is places at the correct sowing depth if the establishment is to be successful. If the optimal conditions prevail, the amount of grass seed can be halved without the yield is affected. If the seeds are spread evenly over the entire field or in lines, have no meaning. Chemical control during the year of the establishment have negative effect on the clover and give no extra yield later on. The choice of protecting crop has no importance as long as the grass and clover gets enough light. The grass benefits if the protecting crop is taken as whole crop silage. The optimal age for the specific grass species depends on the grass type that is most dominant in the mixture. Many high-yielding species drops rapidly after the first two years. In a system with extensive grassland you should from the start carefully decide which species are most suitable. Help seeding can be done with existing drill. Both trailer and coulters are functioning. A common roller equipped with a seed box is also possible. There are also harrows provided with some form of seed boxes and special direct drilling machines. The review of the studies gives different answers. Five of the trials show that using help seeding increases the yield while two tests show that the method doesn’t work. Two trials performed in Ireland, one in New Zealand and two tests conducted in Sweden, all shows increased yield with help seeding. Many of the trials are not credible because the method is not clearly described or are the trials carried out over a too short period of time. Worth mentioning is that several of the trials are almost 20 years old and more modern studies is needed if one wants to claim that help seeding actually works. One of the Swedish trials showing that help seeding does not increase the yield can be seen as very credible. The reason for this is that the trial set up is carefully documented and that both the yield, nutritional and botanical composition are measured for many years. This without any significant differences between the attempt boxes or try places been stated. My conclusions is therefore that help seeding is not likely to be used to counteract the reduced yield of grass in an intensive system, at least not in the Swedish conditions. This is probably due to the new plants will be ousted by the existing grassland. However, it´s possible that help seeding at very low yielding pastures could raise the yield because in extreme situations, there is always the lowest level at which subsequent actions improves performance