TCP Performance in Ad Hoc Networks

Ad hoc networks are mobile wireless networks which do not have any kind of fixed infrastructure. The routing layer in an ad hoc network ties the network together into a seamless entity and provide transparent services to higher layer protocols. This thesis examines the interactions of two routing protocols, AODV and DSR and how the mobile ad hoc network environment affect TCP performance. The results presented here are as follows: the path length and the presence of competing traffic are the main factors of TCP throughput performance. The size of TCP window affects the loss rate, but the loss rate is not strongly correlated to throughput performance. Using TCP selective acknowledgement option does not improve throughput. Finally, there is hardly any difference in TCP throughput when using DSR and AODV. These conclusions are supported by extensive simulation experiments

Is Repeated Testing of Declarative Knowledge in Mathematics Moderated by Feedback?

This study set out to examine the effects of repeated testing of students’ declarative knowledge in mathematics in grade 7 (13-14 years old) and to what extent feedback moderates the effect of continually testing students’ declarative knowledge. Students who have automated the 400 basic arithmetical combinations (200 addition combinations and 200 subtraction combinations) have gained declarative knowledge. Mastering these combinations gives students an advantage where doing various calculations and performing different mathematical procedures are concerned (Dowker, 2012). If a student has automated the basic combinations, their attention will not be diverted from the procedure when solving calculation tasks, and there is thereby less risk of incorrect answers (Dowker, 2012). Previous studies have also shown that declarative knowledge in mathematics predict future results in more advanced mathematics (Hassel Bring, Goin, & Bransford, 1988; Gersten, Jordan, & Flojo, 2005; Rathmell & Gabriele, 2011)

Relationships between Process Parameters, Microstructure and Adhesion Strength of HVOF Sprayed IN718 Coatings

Fundamental understanding of relationships between process parameters, particle in-flight characteristics and adhesion strength of HVOF sprayed coatings is important to achieve the high coating adhesion that is needed in aeronautic repair applications. In this study statistical Design of Experiments (DoE) was utilized to identify the most important process parameters that influence adhesion strength of IN718 coatings sprayed on IN718 substrates. Special attention was given to the parameters combustion ratio, total gas mass flow, spray distance and external cooling, since these parameters were assumed to have a significant influence on particle temperature and velocity. Relationships between these parameters and coating microstructure were evaluated to fundamentally understand the relationships between process parameters and adhesion strength

Distribution of Horse chestnut bleeding canker on trees caused by Pseudomonas syringae pv. aesculi in central parts of Malmö

Sjukdomen kastanjeblödarsjuka orsakad av bakterien Pseudomonas syringae pv. aesculi drabbar hästkastanjer i Europa. Denna kandidatuppsats har som mål att undersöka sambandet mellan uppkomst av kastanjeblödarsjuka, vitalitet, ståndort och sekundera skadegörare i de centrala delarna av Malmö. Kastanjeblödarsjuka är en ny sjukdom som har spridits i Europa de senaste decennierna och bakterien angriper trädets floem och tillslut dödar trädet. Det finns lite forskat kring sjukdomen och inget botemedel som inte går att applicera på träden i verkligheten. Pseudomonas syringae pv. aesculi på hästkastanj återfinns ofta i nordvästra Europa och är mer ovanlig söderut på kontinenten. För att få svar på frågeställningen så har en fallstudie genomförts i form av en inventering på hästkastanjer för att samla in uppgifter kring stamdiameter, vitalitet, ståndort kastanjeblödarsjuka och sekundära skadegörare på hästkastanjer. Den insamlade informationen har sedan analyserats för att få fram resultat. Även en mindre litteraturstudie har gjorts men är inte en del av resultatet utan bör betraktas som bakgrund och förklaring av begrepp och sjukdomar. Den här studien visar på att träd som står i hårdgjord yta drabbas oftare av kastanjeblödarsjuka än de träd som inte står i hårdgjord yta i de centrala delarna av Malmö. Det finns ingen direkt koppling mellan vitalitet och kastanjeblödarsjuka. Det var också för få trädindivider med sekundära skadegörare för att se någon trend. Den här undersökningen är inte tillräckligt stor för att resultatet ska kunna appliceras över hela Malmö eller som en generell beskrivning av vilka träd som bakterien angriper. Om en större inventering genomförs och det framkommer liknade resultat som den här undersökningen så skulle det kunna ge riktlinjer till hur träd bör planteras i framtiden, eller vilka områden som kan komma att bli mer utsatta och kan komma att försvinna träd från. Förhoppningsvis kan detta arbete bli inspiration till mer framtida forskning kring ämnet

Inequality and COVID-19 in Sweden: relative risks of nine bad life events, by four social gradients, in pandemic vs. prepandemic years

The COVID-19 pandemic struck societies directly and indirectly, not just challenging population health but disrupting many aspects of life. Different effects of the spreading virus—and the measures to fight it—are reported and discussed in different scientific fora, with hard-to-compare methods and metrics from different traditions. While the pandemic struck some groups more than others, it is difficult to assess the comprehensive impact on social inequalities. This paper gauges social inequalities using individual-level administrative data for Sweden’s entire population. We describe and analyze the relative risks for different social groups in four dimensions—gender, education, income, and world region of birth—to experience three types of COVID-19 incidence, as well as six additional negative life outcomes that reflect general health, access to medical care, and economic strain. During the pandemic, the overall population faced severe morbidity and mortality from COVID-19 and saw higher all-cause mortality, income losses and unemployment risks, as well as reduced access to medical care. These burdens fell more heavily on individuals with low income or education and on immigrants. Although these vulnerable groups experienced larger absolute risks of suffering the direct and indirect consequences of the pandemic, the relative risks in pandemic years (2020 and 2021) were conspicuously similar to those in prepandemic years (2016 to 2019)

VD-avtal och dess betydelse för anställningstryggheten

The employment law in Sweden is very extensive compared to other countries. My aim with this essay is to compare the employment law for an employee with the employment protection for a CEO. The CEO is not protected by the employment Protection Act and therefore his terms of employment are completely up to the agreement he signs when he begins his employment. To do this I need to recite the main parts of the contract binding the CEO to his company. I need to explain the context of a non-competition clause, clause of secrecy, and furthermore explain how a employment contract for a CEO should look like. The main aim is then to look into which function the contract has in the gap between employment protection and the common contract law. To be able to answer this question, I have during the process of this essay compared four different employment contracts for CEO and compared them with relevant law. The last thing I have done is to look into case law from the Supreme Court and the Labour Court to find how the law and contracts are beeing applied in real life

Green-Lean Synergy - Root-Cause Analysis in Food Waste Prevention

Purpose_The goal of this paper is to explore the possible synergetic effects between lean philosophy and green endeavors in improving resource efficiency in the food sector. To that end, it is investigated how a proper and tailor-made adaptation of the lean six sigma root cause analysis method could help in overcoming the complexities of increased resource efficiency in food production.Design/methodology/approach_The case study concerned reduction of waste at an industrial production line of a dough-based product, through the implementation of the lean six sigma tool.Findings_An achievement of a 50% reduction of waste on the studied process line was reached, thus exceeding the initial improvement goal.Research limitations/implications (if applicable)_While the explicit findings on the specific root causes of waste on this actual production line are not immediately transferrable to other cases, they show that applying this method to identifying and eliminating root causes of waste for other products and processes in the food sector could not only reduce costs but also contribute to more resource-efficient and sustainable industrial food production.Practical implications (if applicable)_ Political and public high interest in environmental and social sustainability associated with food waste render this an important development.Originality/value_ While the potential of linking green and lean efforts has been acknowledged, the application of the lean six sigma methodology for more sustainable food production has not yet been explored. This paper contributes to this researc

Pathways from Childhood Economic Conditions to Adult Mortality in a 1953 Stockholm Cohort: The Intermediate Role of Personal Attributes and Socioeconomic Career

Although both childhood and adult economic conditions have been found to be associated with mortality, independently or in combination with each other, less is known about the role of intermediate factors between these two life stages. This study explores the pathways between childhood economic conditions and adult mortality by taking personal attributes as well as adult socioeconomic career into consideration. Further, we investigate the role of intergenerational income mobility for adult mortality. We used data from a prospective cohort study of individuals that were born in 1953 and residing in Stockholm, Sweden, in 1963 who were followed for mortality between 2002 and 2021 (n = 11,325). We fit Cox proportional hazards models to assess the association of parental income, cognitive ability, social skills, educational attainment, occupational status, and adult income with mortality. The income mobility is operationalized as the interaction between parental and adult income. Our results show that the association between parental income and adult mortality is modest and largely operates through cognitive ability and adult educational attainment. However, our results do not provide support for there being an effect of intergenerational income mobility on adult mortality. In a Swedish cohort who grew up in a comparatively egalitarian society during the 1950s and 1960s, childhood economic conditions were found to play a distinct but relatively small role for later mortality

Användningspotential av biokol i urban miljö

2016 uppskattades det att 54 % av världens populationer bor, arbetar och lever sina liv i städer eller urbana miljöer. I Sverige bor idag 85 % av befolkningen i tätorter jämfört med att 90% av befolkningen bodde på landsbygden på 1800-talet. Förändringen skedde med den industriella revolutionen som förvandlade Sverige från en fattig jordbruksnation till ett välfungerande industriland. I takt med urbaniseringen av städer och utveckling av det politiska samhället, där bostadsbrist drev på en utveckling och städerna som växte till med förorter, kallat urban sprawl. Idag används istället en annan metod för att hantera den ökande urbaniseringen, förtätande av städer. Det gör ytor i städerna eftertraktade och ytorna för vegetationen krymper. Gröna ytor anses vara en del av att skapa hållbara städer vilket bland annat kan mätas i ekosystemtjänster. Det ställer krav på växtligheten som får finnas kvar. Biokol är organiskt material som har förbränts under syrefria förhållanden och har senaste tiden seglat upp som ett potentiellt medel med positiva klimateffekter. Bland annat genom biokolets förmåga att minska växthusgaser, agera som ett jordförbättringsmaterial, rena dagvatten, avfallshantering samt energiproduktion. Som jordförbättringsmaterial är det intressant för att förbättra ståndorter i den urbana miljön. Biokol är inte bara en produkt utan flera beroende på deras fysisk-kemiska egenskaper som bestäms av råmaterial och pyrolysprocess. Dessa egenskaper kan göra att biokol beter sig olika i marken. Det här arbetet är en explorativ undersökning som använder sig av flera olika tekniker som för samman information och data för att kartlägga fakta om biokol och även dess användningspotential i växtbäddar i urbana miljöer. Det består av en litteraturstudie samt intervjuer med Stockholm stad och Göteborgs stad, Uppsala kommun, Peab och Bara mineraler. Det finns en stor potential i användningen av biokol som jordförbättringsmedel i urbana miljöer, men det finns inte tillräckligt med forskning idag som visar på resultat som kan användas i branschen. Fördelarna med biokol går utanför den gröna sektorns gränser. Den stora vinsten med biokol är inte de separata fördelarna utan helheten, det cirkulära tänkandet som kan integreras i den ekologiska livscykeln, är i kombination med varandra en del i ett nytt tankesätt.In 2016, it was estimated that 54% of the world's populations live and work in cities or urban environments. In Sweden, 85% of the population lives in urban areas compared to 90% of the population lived in rural areas in the 19th century. The change took place with the start of the industrial revolution that transformed Sweden from a poor agricultural nation to a well-functioning industrial country. In step with the urbanization of cities and the development of political society, where housing shortages urged a development of cities that grew with suburbs, called urban sprawl. Today another method is used to manage the increasing urbanization: densification of cities. It makes surfaces within the cities attractive for exploitation and the surfaces for vegetation shrink. Green surfaces are considered part of creating sustainable solutions that can be measured in ecosystem services. This require demands on the vegetation and its habitat. Biochar is organic material that has been burned under oxygen-free conditions and has recently been recognized as a potential agent that can produce positive climate effects. Biochar have potential to mitigate greenhouse gases, act as a soil amendment, clean storm water, waste management and energy production. As soil amendment, it can improve the quality of plant beds in the urban environment. The characteristics of biochar is dependent on its physio-chemical properties determined by feedstock and pyrolysis process. These properties can cause the biochar to behave differently in the soil. This work is an exploratory study that use different techniques that bring together information and data to map facts about biochar and also its potential use in plant beds in urban environments. This study consists of a literature study as well as interviews with Stockholm city and Gothenburg city Uppsala municipality, Peab region syd AB and Bara mineraler AB. There is great potential in the use of biochar as soil amendment in urban settings, but there is not enough research today that can confirm results with use of biochar in urban environments. The benefits of biochar are beyond the boundaries of the green sector. The big advantage with biochar is not the separate benefits, but when they come together as a whole that can be integrated into the ecological life cycle