The structured winds of single massive stars can be classified into two broad groups: stochastic structure and organized structure. While the former is typically identified with clumping, the latter is typically associated with rotational modulations, particularly the paradigm of corotating interaction regions (CIRs). While CIRs have been explored extensively in the ultraviolet band, and moderately in the X-ray and optical, here we evaluate radio variability from CIR structures assuming free-free opacity in a dense wind. Our goal is to conduct a broad parameter study to assess the observational feasibility, and to this end, we adopt a phenomenological model for a CIR that threads an otherwise spherical wind. We find that under reasonable assumptions, it is possible to obtain radio variability at the 10 per cent level. The detailed structure of the folded light curve depends not only on the curvature of the CIR, the density contrast of the CIR relative to the wind, and viewing inclination, but also on wavelength. Comparing light curves at different wavelengths, we find that the amplitude can change, that there can be phase shifts in the waveform, and the entire waveform itself can change. These characterstics could be exploited to detect the presence of CIRs in dense, hot winds.

The evolution to 5G and its use cases is driven by data-intensive applications requiring higher data rates over wireless channels. This has led to research in massive multiple input multiple output (MIMO) techniques and the use of the millimeter wave (mm wave) band. Because of the higher path loss at mm wave frequencies and the poor scattering nature of the mm wave channel (fewer paths exist), this thesis first proposes the use of the sphere decoding (SD) algorithm, and the semidefinite relaxation (SDR) detector to improve the performance of a uniform planar array (UPA) hybrid beamforming technique with large antenna arrays. The second contributions of this thesis consist of a low-complexity algorithm using the gradient descent for hybrid precoding and combining designs in mm wave systems. Also, in this thesis we present a low-complexity algorithm for hybrid precoding and combining designs that uses momentum gradient descent and Newton’s Method for mm wave systems which makes the objective function converge faster compared to other iterative methods in the literature; the two proposed low-complexity algorithms for hybrid precoding and combining do not depend on the antenna array geometry, unlike the orthogonal matching pursuit (OMP) hybrid precoding/combining approach. Moreover, these algorithms allow hybrid precoders/combiners to yield a performance very close to that of the optimal unconstrained digital precoders and combiners with a small number of iterations. Simulation results verify that the proposed hybrid precoding/combining scheme that uses momentum gradient descent and Newton’s Method outperforms previous methods that appear in the literature in terms of bit error rate (BER) and achievable spectral efficiency with lower complexity. Finally, an iterative algorithm that directly converts the hybrid precoding/combining in the full array (FA) architecture to subarray (SA) architecture is proposed and examined in this thesis. It is called direct conversion of iterative hybrid precoding/combining from FA to SA (DCIFS) hybrid precoding/combining. The proposed DCIFS design takes into consideration the matrix structure of the analog and baseband precoding and combining in the design derivation. Moreover, it does not depend on the antenna array geometry, unlike other techniques, such as the orthogonal matching pursuit (OMP) hybrid precoding/combining approach, nor does it assume any other constraints. Simulation results show that the proposed DCIFS hybrid design, when compared to the FA hybrid designs counterpart, can provide a spectral efficiency that is close to optimum while maintaining a very low complexity and better spectral efficiency than the conventional SA hybrid design with the same hardware complexity.

In recent years thousands of people worldwide have been using Massive open on- line courses (MOOCs) for various reasons, including career development and change, continuing education, lifelong learning, and training. MOOCs are free online courses that anyone can enroll in and are an affordable and flexible way to learn new skills, develop professionally, and provide quality educational experience across the globe. Having an exemplary user interface will make users prefer most MOOC platforms, which inspired this study to know which MOOC platform has usability and better user experience by using the survey evaluation. The main objective of this study is to measure the usability components(effectiveness, efficiency, and overall user satisfaction level) to determine which MOOC platform, Coursera or Udemy, has a better user experience using the heuristic principles. A quantitative research method has been used in this paper, which focuses on sta- tistical, mathematical, and numerical analysis of data collected through surveys, questionnaires, and polls. In this paper, a questionnaire to determine user satis- faction through surveys has been developed. Usability has been evaluated for each MOOC platform (Coursera and Udemy) by calculating usability components. Sta- tistical methods like variance and standard deviations has been calculated using the survey results. Responses from the survey evaluation are collected and are graphically represented in bar graphs and pie charts. Respondent’s timings and statistical method results are presented in a tabular form. The satisfaction level is calculated and represented in a Likert scale format. The usability of two MOOC platforms (Coursera and Udemy) was measured by cal- culating usability components. Better user experience among Coursera and Udemy is measured using usability heuristic principles. This study concludes that effec- tiveness, efficiency, and satisfaction level while performing eight tasks given to the user is similar in both MOOC platforms (Coursera and Udemy). From the survey evaluation, the users preferred Udemy over Coursera.

The complexity of advanced antenna techniques used in the new generation of wireless networks (5G) makes communication between experts and non-technical staff more difficult than ever. As cooperation between network vendors and network operators affects the adoption of the new standard, a need for a new tool has emerged to make technical presentations more engaging and compelling. This thesis presents an exploratory study that aims to examine various design options for an interactive visualization of radiowave propagation to be used by advanced antenna systems experts. Through a Research-oriented Design, functional and non-functional requirements were identified with the help of domain expert. Later, an interactive prototype was designed and developed using a participatory design approach. Qualitative and quantitative data was gathered through usability testing, System Usability Scale (SUS) questionnaires and semi-structured interviews conducted with 12 researchers and engineers at Ericsson AB a multinational telecommunication company. User evaluation proved that such a tool could facilitate communication between technical experts and non-technical staff. The developed prototype was considered intuitive and useful by the majority of study participants as measured by interviews and the SUS survey. Future research is encouraged to include the target audience representatives in order to measure their engagement while using the tool. / Komplexiteten hos avancerade antenntekniker som anvnds i den nya generationen av mobilntverk (5G), gr kommunikationen mellan experter och icke-teknisk personal svrare n ngonsin. Eftersom samarbetet mellan telekommunikationsfretag och ntoperatrer pverkar anpassningen av den nya standarden, har behovet av ett nytt verktyg uppsttt fr att gra tekniska presentationer mer engagerande och vertygande. Avhandlingen presenterar en underskande studie som syftar till att underska olika designalternativ fr en interaktiv visualisering av radiovgsfrkning som anvnds av avancerade antennsystems experter. Genom en forskningsinriktad design identifierades funktionella och icke-funktionella krav med hjlp av en domnexpert. Senare konstruerades och utvecklades en interaktiv prototyp med hjlp av en co-operativ designmetod. Kvalitativa och kvantitativa data samlades in genom anvndbarhetstester, System Usability Scale (SUS) frgeformulr och halvstrukturerade intervjuer med 12 forskare och ingenjrer p Ericsson AB ett multinationellt telekommunikationsfretag. Anvndarutvrdering visade att ett sdant verktyg skulle underltta kommunikationen mellan tekniska experter och icke-teknisk personal. Den utvecklade prototypen ansgs intuitiv och anvndbar av majoriteten av studiedeltagarna, mtt genom intervjuer och SUS-underskningen. Framtida forskning uppmuntrar till att inkludera mlgruppsrepresentanterna fr att mta deras engagemang medan de anvnder verktyget.

Concrete is the most common building material in the world and it consists of aggregates,cement and water that harden over time, it is also known as a composite material. The use ofconcrete is very versatile due to its resistance to wind and water and its ability to withstandhigh temperature. These qualities make concrete a suitable building material for largestructures such as dams.A dam is a huge construction that needs massive amount of concrete to build it with and thatleads to high cost, so alternative methods should be considered to minimize the cost ofconstructing the dams. One method is building the dams with Roller Compacted Concrete(RCC), which by definition is a composite construction material with no-slump consistency inits unhardened state and it has achieved its name from the construction method. The definitionfor a no-slump consistency is a freshly mixed concrete with a slump less than 6 mm. TheRCC is placed with the help of paving equipment and then it is compacted by vibrating rollerequipment. The RCC ingredients are the same as for the conventional concrete but it hasdifferent ratios in the materials that are blended to produce the concrete. It differs when itcomes to aggregates because both similar aggregates used in conventional concrete oraggregates that do not fulfill the normal standards can be used in the RCC mixtures. Thismeans, for example that aggregates found on the construction site can be used for the RCC.Compared to when constructing a conventional concrete dam, which is usually built in largeblocks, the RCC dam are usually built in thin, horizontal lifts, which allows rapidconstruction. This reduces the amount of formwork, but also the demand for man-hours areless due to the usage of machines for spreading and compacting, ultimately making it acheaper method. Building with RCC has become very popular around the world because of itsadvantages and new methods have been developed over the past two decades, adapted to theexperience gained after each project. All RCC dams that has been built, usually faceschallenges both during and after construction, and it includes everything from temperaturevariations, cracks to leakage.The main purpose of this master thesis is to create a guideline for how to design and constructdams with RCC and the idea is to be able to use it as a basis for future dams. Therequirements of Eurocode 2 and RIDAS are the basis of the criteria that the dam must fulfilland information of what is expected of the RCC is presented in this thesis. Furthermore anexample for design of an existing embankment dam to an RCC dam has been presented in thisthesis. The embankment dam needs to be rebuilt in order to increase the safety of the dam andthe goal of the case study was to determine the dimensions of the new RCC dam. / Betong är det vanligaste byggmaterialet i världen och det är ett material som består av ballast,cement och vatten som härdas över tiden, även känt som ett komposit material. Användningenav betong är mycket mångsidig tack vare dess motståndskraft mot vind och vatten och dessförmåga att motstå höga temperaturer. Dessa egenskaper gör betong ett lämpligt byggmaterialför stora strukturer som dammar.En dam är en enorm konstruktion som kräver massiva mängder av betong för att bygga denmed och det leder till höga kostnader, därför bör alternativa metoder övervägas för attminimera dessa. Ett förslag till en metod är att bygga dammar med Roller CompactedConcrete (RCC), som per definition är ett komposit material med ett sättmått på mindre än 6mm i sitt ohärdade tillstånd. RCC har erhållit sitt namn från sin byggmetod, då den sprids medhjälp av utrustning för att lägga vägar och sedan kompakteras den med en traktordrivenvibratorvält. Ingredienserna för RCC är samma som för konventionell betong, men den storaskillnaden utgörs av att det är olika mängd-förhållanden av de material som blandas för attproducera denna betong. Det skiljer sig också när det gäller ballasten, eftersom både liknandeballast som används i konventionell betong eller ballast som inte uppfyller de normalastandarder kan användas för RCC. Det betyder att exempelvis, ballast som man erhåller påbyggarbetsplatsen kan användas för att producera RCC.I jämförelse med när man bygger en traditionell betongdamm, som vanligen byggs i storablock, så bygger man oftast en RCC damm i horisontella lager vilket ger möjligheten försnabbt byggande. Detta reducerar behovet av att använda gjutformar, men även antaletmantimmar på grund av användningen av maskiner för spridning och kompaktion. De härfaktorerna gör det till en billigare metod. RCC dammar har blivit populärt att bygga runt om ivärlden på grund av dess fördelar och nya metoder har utvecklats under de senaste 20 årenanpassade efter erfarenheten man har erhållit efter varje projekt. Alla RCC dammar sombyggts stöter ofta på utmaningar både under och efter byggandet och det har med, allt fråntemperatur variationer, sprickor, och läckage, att göra.Huvudsyftet med det här examensarbetet är att skapa en guide för hur man designar ochbygger en RCC damm och tanken är att man ska kunna använda den som en grund förframtida dammbyggen. Kraven från Eurokod 2 och RIDAS är grunden för kriterierna somdammen ska uppfylla och information om vad som förväntas av RCC är presenterat. Enfallstudie har gjorts, där ett exempel på en design för en RCC damm som ska ersätta enbefintlig fyllningsdamm i Hylte är presenterad. Fyllningsdammen är i behov av ombyggnationför att höja säkerheten av dammen och målet med fallstudien är att avgöra dimensionerna förden nya RCC dammen som ska placeras där.

We present time-resolved and phase-resolved variability studies of an extensive X-ray high-resolution spectral data set of the δ Ori Aa binary system. The four observations, obtained with Chandra ACIS HETGS, have a total exposure time of ≈ 479 ks and provide nearly complete binary phase coverage. Variability of the total X-ray flux in the range of 5–25 Å is confirmed, with a maximum amplitude of about ±15% within a single ≈ 125 ks observation. Periods of 4.76 and 2.04 days are found in the total X-ray flux, as well as an apparent overall increase in the flux level throughout the nine-day observational campaign. Using 40 ks contiguous spectra derived from the original observations, we investigate the variability of emission line parameters and ratios. Several emission lines are shown to be variable, including S xv, Si xiii, and Ne ix. For the first time, variations of the X-ray emission line widths as a function of the binary phase are found in a binary system, with the smallest widths at ϕ = 0.0 when the secondary δ Ori Aa2 is at the inferior conjunction. Using 3D hydrodynamic modeling of the interacting winds, we relate the emission line width variability to the presence of a wind cavity created by a wind–wind collision, which is effectively void of embedded wind shocks and is carved out of the X-ray-producing primary wind, thus producing phase-locked X-ray variability. Based on data from the Chandra X-ray Observatory and the MOST satellite, a Canadian Space Agency mission, jointly operated by Dynacon Inc., the University of Toronto Institute of Aerospace Studies, and the University of British Columbia, with the assistance of the University of Vienna.

X-ray emission from stars much more massive than the Sun was discovered only 35 years ago. Such stars drive fast stellar winds where shocks can develop, and it is commonly assumed that the X-rays emerge from the shock-heated plasma. Many massive stars additionally pulsate. However, hitherto it was neither theoretically predicted nor observed that these pulsations would affect their X-ray emission. All X-ray pulsars known so far are associated with degenerate objects, either neutron stars or white dwarfs. Here we report the discovery of pulsating X-rays from a non-degenerate object, the massive B-type star ξ1 CMa. This star is a variable of β Cep-type and has a strong magnetic field. Our observations with the X-ray Multi-Mirror (XMM-Newton) telescope reveal X-ray pulsations with the same period as the fundamental stellar oscillations. This discovery challenges our understanding of stellar winds from massive stars, their X-ray emission and their magnetism.

Yes / Recent studies and research have centred on new solutions in different elements and stages to the increasing energy and data rate demands for the fifth generation and beyond (B5G). Based on a new-efficient digital beamforming approach for 5G wireless communication networks, this work offers a compact-size circular patch antenna operating at 60 GHz and covering a 4 GHz spectrum bandwidth. Massive Multiple Input Multiple Output (M–MIMO) and beamforming technology build and simulate an active multiple beams antenna system. Thirty-two linear and sixty-four planar antenna array configurations are modelled and constructed to work as base stations for 5G mobile communication networks. Furthermore, a new beamforming approach called Projection Noise Correlation Matrix (PNCM) is presented to compute and optimise the fed weights of the array elements. The key idea of the PNCM method is to sample a portion of the measured noise correlation matrix uniformly in order to provide the best representation of the entire measured matrix. The sampled data will then be utilised to build a projected matrix using the pseudoinverse approach in order to determine the best fit solution for a system and prevent any potential singularities caused by the matrix inversion process. The PNCM is a low-complexity method since it avoids eigenvalue decomposition and computing the entire matrix inversion procedure and does not require including signal and interference correlation matrices in the weight optimisation process. The suggested approach is compared to three standard beamforming methods based on an intensive Monte Carlo simulation to demonstrate its advantage. The experiment results reveal that the proposed method delivers the best Signal to Interference Ratio (SIR) augmentation among the compared beamformers

This thesis is a study of massive star formation: the environments in which they form and the effect that their radiation feedback has on their environments. We present high-performance supercomputer simulations of massive star formation inside molecular cloud clumps and cores. First, we present a novel radiative transfer code that hybridizes two previous approaches to radiative transfer (raytracing and flux-limited diffusion) and implements it in a Cartesian grid-based code with adaptive mesh refinement, representing the first of such implementations. This hybrid radiative transfer code allows for more accurate calculations of the radiation pressure and irradiated gas temperature that are the hallmark of massive star formation and which threaten to limit the mass which stars can ultimately obtain. Next, we apply this hybrid radiative transfer code in simulations of massive protostellar cores. We simulate their gravitational collapse and the formation of a massive protostar surrounded by a Keplerian accretion disk. These disks become gravitationally unstable, increasing the accretion rate onto the star, but do not fragment to form additional stars. We demonstrate that massive stars accrete material predominantly through their circumstellar disks, and via radiation pressure drive large outflow bubbles that appear stable to classic fluid instabilities. Finally, we present simulations of the larger context of star formation: turbulent, magnetised, filamentary cloud clumps. We study the magnetic field geometry and accretion flows. We find that in clouds where the turbulent and magnetic energies are approximately equal, the gravitational energy must dominate the kinetic energy for there to be a coherent magnetic field structure. Star cluster formation takes place inside the primary filament and the photoionisation feedback from a single massive star drives the creation of a bubble of hot, ionised gas that ultimately engulfs the star cluster and destroys the filament. / Thesis / Doctor of Philosophy (PhD)

In the modern building industry wood as a building material has been looked on as one of the solutions to lower the environmentally impact of the building industry. Building types that normally have been reserved for concrete and steel are today being built with wood as main load bearing component. However, the structural robustness of high-rise wood building has been questioned. The concern relates to wood’s brittle failure-mode and therefore the capacity of wood buildings to withstand catastrophic events where a loadbearing structural part its removed from the construction. To counteract a brittle failure mode in wood and create a ductile failure mode that allows alternative load paths, ductile steel connectors are seen as a solution. With inspiration from the concrete and steel industry, catenary action is brought forward as the most efficient method to create an alternative load path in high-rise wood buildings. To create catenary action, a tube connector that allows excessive deformation with increasing strength was believed to have sufficient capacity. A test method for testing tube connector capacity in a catenary event was developed with a main focus on tube capacity and forces created on the surrounding structure in a catastrophic event. To achieve this, a long stroke reversed 4-point bending test was formed and testing of traditional fasteners and the tube connector was conducted. Test result from catenary capacity testing showed low to no capacity for traditional fastening methods, however, traditional fastening method created arcing action in the beginning of the test cycles. The traditional fasteners showed a consistency in failure mode with arching and wood crushing before connection failure in form of screw withdrawal. Tube connectors had low to no consistency in failure modes, but higher consistency in capacity. Failure mode regarding tubes consisted of steel failure in tube and wood failure in the test specimen. In general, the tubes connector showed promising capacity and ductility to create alternative load paths with the help of catenary action. The project has shown that some design development for the tube connector and lager scale testing are needed to completely understand tube connector capacity and failure mode.