We consider the problem of secure communications in a Gaussian two-way relay network where two nodes exchange confidential messages only via an untrusted relay. The relay is assumed to be honest but curious, i.e., an eavesdropper that conforms to the system rules and applies the intended relaying scheme. We analyze the achievable secrecy rates by applying network coding on the physical layer or the network layer and compare the results in terms of complexity, overhead, and efficiency. Further, we discuss the advantages and disadvantages of the respective approaches.

Preventing the success of active attacks is of essential importance for network coding since even the infiltration of one single corrupted data packet can jam large parts of the network. The existing approaches for network coding schemes preventing such pollution attacks can be divided into two categories: utilize cryptographic approaches or utilize redundancy similar to error correction coding. Within this paper, we compared both paradigms concerning efficiency of data transmission under various circumstances. Particularly, we considered an attacker of a certain strength as well as the influence of the generation size. The results are helpful for selecting a suitable approach for network coding taking into account both security against pollution attacks and efficiency.

Growing memory capacities and the increasing number of cores on modern hardware enforces the design of new in-memory indexing structures that reduce the number of memory transfers and minimizes the need for locking to allow massive parallel access. However, most applications depend on hard durability constraints requiring a persistent medium like SSDs, which shorten the latency and throughput gap between main memory and hard disks. In this paper, we present our winning solution of the SIGMOD Programming Contest 2011. It consists of an in-memory indexing structure that provides a balanced read/write performance as well as non-blocking reads and single-lock writes. Complementary to this index, we describe an SSD-optimized logging approach to fit hard durability requirements at a high throughput rate.

Measuring the energy consumption of software components is a major building block for generating models that allow for energy-aware scheduling, accounting and budgeting. Current measurement techniques focus on coarse-grained measurements of application or system events. However, fine grain adjustments in particular in the operating-system kernel and in application-level servers require power profiles at the level of a single software function. Until recently, this appeared to be impossible due to the lacking fine grain resolution and high costs of measurement equipment. In this paper we report on our experience in using the Running Average Power Limit (RAPL) energy sensors available in recent Intel CPUs for measuring energy consumption of short code paths. We investigate the granularity at which RAPL measurements can be performed and discuss practical obstacles that occur when performing these measurements on complex modern CPUs. Furthermore, we demonstrate how to use the RAPL infrastructure to characterize the energy costs for decoding video slices.

Daggkåpan är en förskola som projekterats i passivhusteknik. Förskolan är en naturförskola, vilket främst innebär att i stort sett all verksamhet bedrivs utomhus. Byggnaden är i två plan vilket gör att tomtarean kan utnyttjas till mer utomhusvistelse. Förutsättningar för att bedriva verksamheten inomhus finns även. Utomhusmiljön och inomhusmiljön hos Daggkåpan smälter samman och barnen kan lätt ta ett steg ut till naturen från sina hemvister. Detta innebär att antalet utgångar ökar. En solcellsanläggning genererar all elektricitet och gör byggnaden självförsörjande. Byggnadens varmvatten och värme står solfångare för. I takt med bostadsutvecklingen blir även behovet av förskolor större. Att skaffa kunskap och erfarenheter om energieffektivt byggande är idag en god idé eftersom alla byggnader på sikt måste vara så energieffektiva som möjligt. En av hörnpelarna med att bygga passivhus är att låta ett genomtänkt och energieffektivt byggnadsskal ersätta ett konventionellt värmeförsörjningssystem. Genom att förbättra konstruktioner och hålla koll på byggprocessen kan andra delar av byggnaden förenklas och i vissa fall helt ersättas. Det som fördyrar i ena änden kan leda till en god investering i den andra. Utmaningen med passivhus är att systematisera, se helheter och sammanhang och framför allt eftersträva det enkla. Enkla system ger låga drift- och underhållningskostnader och risken för driftstörningar minskar. Den största delen av värmen är gratis. Den kommer från instrålande sol, värme från människor och spillvärme från apparater och matlagning. Grundkravet är att byggnaden har ett värmeeffektbehov under 10 W per kvadratmeter vid +20ºC inomhus på årets kallaste dag, definierat av dimensionerande utetemperatur. Byggnaden får max läcka 0,3 l/s, m² oms vid +/- 50 Pa tryckskillnad. För att uppnå god komfort krävs välisolerade väggar, solavskärmningar, energieffektiva fönster och dörrar, små köldbryggor och ett bra ventilationssystem där värmen från insidan av huset återvinns. Antalet passivhus i Sverige ökar snabbt, men det är fortfarande småhusen som dominerar. Att bygga en förskola som passivhus är en god idé ur flera synvinklar; Bland annat för att de täta och välisolerade väggarna stänger ute buller och oljud. Även mellanväggar isoleras och bidrar till en extra tyst byggnad. Dessutom blir barnen miljömedvetna eftersom de får vara delaktiga i energieffektivisering. -En viktig aspekt för framtiden. Barnen bidrar själva till uppvärmning av lokalerna genom kroppsvärmen. Undersökningar har bland annat visat att barn som får vistas utomhus är friskare, mer självgående, mer kreativa och klokare. Det ultimata är att använda sig av utemiljöer som ett extra rum för förskolan. Detta leder till minskad byggnadsarea och mindre byggmaterial krävs. Pedagogiken Reggio Emilia använder sig just utav detta begreppet "Uterummet som ett extra rum för verksamheten". Barnen får därmed röra sig fritt i utemiljö, utveckla sina sinnen i en rik fantasivärld, inspireras och samverka med natur och hållbarhet. / Daggkåpan is a preschool projected in passive house technology. The preschool is a nature preschool, which means the activity is mainly out door. It is a two floor building which gives conditions to use the area for more outdoor activities. Conditions for drive the preschool indoors is possible as well. The garden and the inside rooms are connected to each other by the exterior rooms and it is easy for the children just to take a step out to the garden from their residences. A solar cell system generates electricity to the building and makes it self-supplied. The residential development leads to the need of preschools. To obtain knowledge of energy effective constructions is a good idea as the buildings in the future have to be as energy effective as possible. One of the most important things by use the passive house technology is letting a well measured and energy- effective building shell replace a conventional heat supply. By improvement of the construction and focus on the process other parts of the building can be simplified and some can be replaced. What is expensive in one end can lead to a good investment in the other. The challenges with passive house are to systematize, see whole parts and contexts and especially to seek after the simple. Easy systems give low operations- and service-costs and reduce fear of disruptions. Most of the heat is for free. It comes from insulation, human heat and heat from cooking and technologies. Basic requirements for this type of building is a need of heat-output under 10 W per square-meter at an indoor temperature of 20 degrees on the coldest day of the year, defined of the dimensioned outdoor- temperature. The maximum of leak is 0,3 liters per second and square meter at +/- 50 Pa. To receive high comfort it claims well-isolated walls, shadings, energy-effective windows and doors, small thermal bridges and a good ventilation-system where the indoor heat recycles. The number of Passive houses increases, dominated of small houses. Building a preschool as a passive house is a good idea from several perspective; the well-isolated walls leaves out the noise, even the intermediate walls isolates and contributes to a silent building. The children get environmentally conscious as well and take notes of the energy- effectively. - A very important aspect for the future. The children contributes them self of heat to the building by their body heat. Investigations has been shown that outdoor playing children is more healthy, self-propelled, more creative and more clever. The most ultimate is so use patios as an extra room for the preschool activities. The pedagogy Reggio Emilia uses this concept. The children can consequently feel free staying outside, developing their minds in an imaginative environment, inspired of the interaction of the nature and sustainability.

Recent studies have shown that there are currently more than 1.08 billion of Smartphones in the world, with around 89% of them used throughout the day. On average each of these users transfers more than 450 Mbytes per month via either a cellular network or a Wi-Fi network. So far it has been up to the user to decide which one of these two networks to use at each particular moment. In this master’s thesis, the potential energy savings that could be achieved by means of automating the choice of network interface are explored. This way, the user equipment itself would be able to initiate handovers from one radio access technology to another depending on each particular service and on the environmental conditions, and hence it could extend its battery life. The work has focused in energy efficient vertical handovers (VHOs) between Long-Term Evolution (LTE) and Wi-Fi networks. The rapid growth and increasing interest in LTE networks have been the main reasons why these networks have been chosen over Third Generation Mobile Networks. Nevertheless this work can be easily extended to other radio access technologies such as WiMAX (Worldwide Interoperability for Microwave Access) or UMTS (Universal Mobile Telecommunication System). During the thesis project, the potential energy savings via VHOs depending on the type of service have been studied, as well as the different processes involved in a handover decision process. In order to do so, an energy consumption profile of each interface has been built, the different services have been modeled, and a heterogeneous scenario with Wi-Fi and LTE networks has been simulated. The thesis presents how these savings change within each service and with the environmental conditions (network load, interferences). The results show that large energy savings can be achieved. Nevertheless, the potential savings for each different user device can significantly differ. The VHO decision process includes two main aspects that need further study: investigating energy efficient ways of discovering accessible Wi-Fi access points and measuring the available throughput in each network at the moment of the decision. In addition, within LTE-Advanced and HetNets (Heterogeneous Networks), a lot of research regarding how LTE operators can offload traffic to smaller networks is being performed. These smaller networks consist basically of LTE micro cells and Wi-Fi. Both the energy savings and the potential energy expenses of offloading different kinds of traffic to a Wi-Fi network were also studied in this master’s thesis project, using the same approach described in the previous two paragraphs. / Enligt beräkningar så finns det nu mer än 1.08 miljarder smarta telefoner i världen, och ungefär 89% av dem används varje dag. Varje användare överför mer än 450 megabyte per månad i genomsnitt, antingen via cellulära mobilnät eller Wi-Fi. För närvarande är det användaren som avgör vilket av dessa interface som ska användas vid varje tidpunkt. I detta examensarbete utvärderas vilka energibesparingar som kan uppnås genom att automatisera valet av nätverksinterface. På detta vis skulle den mobila enheten själv utföra handover från en radioaccessteknik till en annan beroende på aktiva tjänster och på radioomgivningen, och därmed utöka batteriets livstid. Detta examensarbete fokuserar på vertikal handover mellan LTE och Wi-Fi nätverk. Den snabba tillväxten och det ökande intresset för LTE är den främsta anledningen till att LTE har valts istället för 3G. Det är dock möjligt att med små förändringar generalisera arbetet till andra radioaccesstekniker, till exempel WiMAX eller UMTS. De potentiella energibesparingarna genom vertikala handovers för olika typer av tjänster har studerats, liksom de olika stegen i handover-beslutsprocessen. För detta syfte har en energikonsumtionsprofil skapats för varje interface, de olika tjänsterna har modellerats och ett scenario med Wi-Fi- och LTE-nätverk har simulerats. Denna rapport beskriver hur dessa energibesparingar ändras för varje tjänstetyp och med ändringar av omgivningen (nätverkslast och interferens). Resultaten har visat att stora energibesparingar kan uppnås, även om dessa besparingar kan variera mycket för olika UEs. Beslutet om vertikal handover inkluderar två huvudsakliga aspekter som kräver fortsatta studier: energieffektiva metoder för att upptäcka tillgängliga WiFi-accesspunkter som går att ansluta sig till och mätning av den upplevda datahastigheten i varje nätverk före beslutet om vertikal handover tas. Parallelt med detta examensarbete pågår omfattande studier om hur mobiloperatörer kan avlasta datatrafik till basstationer med kortare räckvidd. Dessa småskaliga nätverk förväntas bestå av LTE mikro/pico celler och/eller Wi-Fi nätverk. Detta examensarbete inkluderar även studier av de potentiella energibesparingar eller energikostnader för att avlasta olika slags trafik till Wi-Fi nätverk.

This work describes three alternative processes for producing microfibrillated cellulose (MFC) in which pulp fibres are first pre-treated and then homogenized using a high-pressure homogenizer. In one process, fibre cell wall delamination was facilitated with a combined enzymatic and mechanical pre-treatment. In the two other processes, cell wall delamination was facilitated by pre-treatments that introduced anionically charged groups into the fibre wall, by means of either a carboxymethylation reaction or irreversibly attaching carboxymethyl cellulose (CMC) onto the fibres. All three processes are industrially feasible and enable production with low energy consumption. Using these methods, MFC can be produced with an energy consumption of 500–2300 kWh/tonne, which corresponds to a 91–98% reduction in energy consumption from that presented in earlier studies. These materials have been characterized in various ways and it has been demonstrated that the produced MFCs are approximately 5–30 nm wide and up to several microns long. / <p>QC 20120928</p>

Purpose: This degree project aims to see how the energy demand from active heating of detached houses can be improved to meet the energy performance requirements set for nearly zero-energy buildings by Boverket (The Swedish National Board of Housing, Building and Planning). Method: To accomplish this, the benefits from two different energy-saving installations are studied: bedrock heat pumps and heat exchangers in Heat Recovery Ventilation Systems (HRV-systems). These are then compared in a new and an older detached house with very different heat losses. There are several reports of energy-saving systems in detached houses. What distinguishes this work is that it compares the specific results from the added energy-saving system depending on whether it was added first or last. The older detached house is an important part of this work as it represents a possible impact on parts of the existing housing stock with a similar technical standard. The energy balance for the buildings is calculated monthly with all contributions from passive heat considered, and with the energy demand for active heating as the main result. Results: It is very difficult to meet the energy performance requirements for an older detached house without extensive measures or renovations. The HRV-system had a low to very low impact. Both types of detached houses have a lot to gain from an investment in bedrock heating, especially the older one that has high energy demands. However, the new detached house with a higher technical standard in the building envelope, was the only one to meet the energy requirements with the bedrock heat pump on its own. Conclusion: Bedrock heating can be a very profitable investment as it provides heat both for the active heating of the building as well as for the domestic hot water. In order to meet tougher energy requirements, the bedrock heat pump may need to be accompanied by an improved and more energy-efficient building envelope and the supply of self-produced electricity, such as solar cells. HRV-systems require a good air tightness and an energy-efficient building envelope to be profitable. In older detached houses, it is not a profitable investment, as it does not have sufficiently large proportions of controlled ventilation to work with. In newer houses the proportion of controlled ventilation is bigger, but the amount of heat loss that can be affected is still not as big as the energy savings a bedrock heat pump can bring.

Magnetic Shape Memory (MSM) alloys show a superelastic behaviour with possible deformation rates up to 6% until 12% and a sufficient lifetime performance [1, 2]. In this paper, a passive application for a superelastic Ni-Mn-Ga-alloy is presented by using the MSM element as an accurately defined inner friction in a system of a multistable actuator, in particular a multistable proportional valve. The multistable valve is characterized by a currentless holding of the valve displacement in any position of the stroke. This circumstance makes the concept a very low energy consumption valve, compared to conventional proportional valves with solenoid actuators. The new aspect of a rigid connection of MSM Materials enables an absorption of tension as well as compressive forces. To realize an applicable controlling valve, a simple and effective controlling strategy has been implemented. Due to the stabilizing effect of the MSM element, an accurate controlling of the valve stroke and the usage for example as a pressure-, mass-flow or temperature-controlling valve was made possible. Furthermore, some potential applications in pneumatics as well as in hydraulics are presented.

Purpose: The purpose with this project was to evaluate the environmental, social, and economic aspects regarding two climate positive buildings in Västerås municipality in Sweden. The company responsible for the buildings, ETC Bygg AB, has assigned this task tothe research group Future Energy Center (FEC) at Mälardalen University. Method: The buildings was simulated with the programs IDA ICE and PVGIS to obtain the overall energy consumption and building efficiency as well as the PV system potential. Regarding transportation, vehicle and driver statistics was studied and adapted to the case study to estimate the tenant’s climate impact. Results: The results showed that the electricity obtained from the PV system both covers the building’s, and tenant’s estimated yearly electricity consumption, but also with a surplus available for storage or selling. The simulatedresults were compared to several previous studies with similar outcome, but with slightly different results. The tenants need for climate friendly transportation resulted in a suggestion of an electric mobility station consisting of electric cars, mopeds, and bicycles to lower the tenants carbon mitigation, costs, and energy consumption. Conclusions: Conclusions from the study was that the buildings meet both the BBR, and the FEBY18 Gold requirements with their high energy efficiency, as well as that the solar power system most likely will produce enough energy to cover both building, and tenant power consumption. A conclusion can be made that the transition to electric transportation have a potential to save both a considerable amount of energy and money for the tenants, but also the possibility to lower their collective yearly carbon mitigation. Also, that the life in a climate positive building have mostly, if not only, positive impacts on its residents.