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Structural Investigation of an Alternative Cordwood Binder
(2026) Stålhammar, Olof
Cordwood masonry is a vernacular building technique that utilizes short pieces of wood in a binder matrix. The binder matrix used today is usually cement, lime-mortar or clay all with various downsides including thermal bridging, high environmental impact or difficulties of separating the materials at end of life. A novel binder made of a mixture of starch-based glue, lignin and saw dust is investigated to determine if the mechanical properties make it suitable to serve as an alternative. Samples of the binder are tested experimentally to find how it reacts to an outdoor environment and compressive strength. The parameters are used to develop a model of a wall element for FE-analysis that is compared with calculations based on Eurocode to verify the suitability of the material. This thesis found the best binder candidate to be one with two parts lignin and one part saw dust. This binder has a compressive strength of 0.4 N/mm2 and a modulus of elasticity of 13.7 N/mm2. This is sufficient for walls in a one-story building according to both the Eurocode calculations and the FE-model. This binder candidate withstood the weather during the three-month trial with only little damage while other candidates partially dissolved after 30-40 days in an exposed environment. The binder performed even better in a semi-sheltered environment, with little to no visible damage.
Torsional Wind Response in Asymmetrical Timber Buildings - A Parametric Study of Plan Irregularity in Mid-Rise Structures
(2026) Dahlgren, Rebecka
Wind loading often governs the lateral response of mid-rise timber buildings and can be critical for torsion, since the structure may rotate in addition to swaying. This thesis applies a parametric modal study of rectangular and L-shaped timber floor plans to identify when torsion governs the fundamental mode, and which stabilizer layouts most effectively reduce torsional sensitivity. The study is limited to the chosen investigated plan sizes and the structural configuration is based on a 6×6 m column grid with constant span lengths, rigid diaphragm action, and stabilizing systems modelled using CLT shear walls and (where applicable) a core, whose lengths, and positions are varied parametrically. Effects such as openings/discontinuities, height/vertical irregularities, connection flexibility, additional bracing systems, and explicit wind-response/comfort checks are outside the scope. Across both geometries, torsion is governed by the combined effect of (i) eccentricity, e, between the center of mass (CM) and the center of rigidity/rotation (CR), expressed as the normalized measure e/D, where D is the plan diagonal, and (ii) the torsional resistance provided by stabilizer lever arms, represented by the normalized torsional stiffness R =qKθ/(Kx + Ky). Here, Kθ is the torsional stiffness about CR, while (Kx and (Ky are the total lateral bending stiffnesses resisting sway in the global x- and y-directions. For rectangular plans, torsion becomes consistently likely once eccentricity is high. In the compiled results, configurations with a normalized eccentricity over the diagonal of the building plan (D), e/D ≥ 0.16 fall in the torsion-dominated region, while configurations with sufficiently high normalized torsional stiffness (R) (about R ≥ 13.5 m) remain translation-dominated. The most efficient torsion-reducing measures in the rectangular study were therefore avoiding stabilizer asymmetry that shifts CR (especially off-centre core placement) and increasing lever arms by placing stabilizers toward façades/corners. For L-shaped plans, torsion sensitivity is generally higher because geometric effects make low eccentricity harder to achieve in practice, so robustness relies more strongly on torsional resistance. In the combined L-shape summary, the key stiffness thresholds are Rcrit,1=10.0 m and Rcrit,2=28.11 m, with corresponding boundary ratios (R/(e/D)) of roughly 128 and 184. Practically, configurations below the lower stiffness level are consistently torsion-prone, whereas for moderate eccentricities, maintaining R above the upper level is associated with translational behaviour. The most effective measures in the L-shape study were moving stabilizers toward the plan corners and avoiding pronounced directional stiffness imbalance, which was shown to broaden the range of torsion-dominated configurations. Overall, the analyses indicate that the most efficient design takes are (1) controlling eccentricity by limiting CR shifts (dominant for rectangles), and (2) maximizing stabilizer lever arms/torsional resistance (dominant for L-shapes). Configurations combining high eccentricity with low torsional resistance are the most torsion-sensitive and should be prioritized for detailed wind-serviceability verification.
Design and Development of a Broadband Power Divider for Millimeter-Wave Applications in Radio Astronomy
(2026) Koc, Arev
Optimizing Urban Energy Flows: Theoretical Insights into Energy Sharing Between Buildings
(2026) Gustafsson, Anton
Space heating and cooling of buildings make up a substantial part of the total energy use globally. Apart from reducing the energy demand, improvements could be made to the energy supply of buildings. Such an improvement could be achieved by utilizing waste energy sources and connecting buildings with different energy demands. This master’s thesis evaluates the performance of a thermal source network (TSN), seen as the fifth generation of district heating and cooling or as a subclass to the fourth generation. A TSN has the ability to time shift energy through balancing units such as geothermal storage, extracting energy through heat pumps and chillers at demand. The project studied a fictional district and compared multiple variations of a TSN to a traditional district heating and cooling (DH/DC) or geothermal base case. The fic tional district consisted of four buildings, both residential and commercial, and used a supermarket as a waste heat source. The heating and cooling demand for the fictional district was 1 448.2 MWh and 860.2 MWh, respectively. Resulting in an remaining heating demand of 588.0 MWh or as a 1.7:1 ratio between the heating and cooling de mand. The study concluded that the DH/DC solution has the lowest investment cost but the highest operational cost and CO2 emissions. As a result of an improved co efficient of performance (COP), the TSN was found to have a lower operational cost and CO2 emissions than both the DH/DC solution and the geothermal solution, but at a higher investment cost. The optimized iteration of the TSN case study, using net work temperatures adjusted to a geothermal storage of boreholes, was deemed to be the most realistic. Compared to the DH/DC solution, the optimized iteration resulted in an increase of 107% in investment cost, a reduction of 84% in operational cost and a reduc tion of 23% for CO2 emissions. A result that also can be presented as a payback time of 2.6 years. Compared to a geothermal base case, the investment cost for the optimized iteration was 17% higher, the operational cost was 4% lower and the CO2 emissions were reduced by 14%. Resulting in a payback time of 91.0 years, a consequence of the assumed redundancy investment of a DH/DC connection. If this connection is omitted and redundancy is achieved in another way, the TSN might result in a lower investment cost than the geothermal base case.
A Comparison of Quantum Gate Optimization Techniques
(2026) Lindgren, Pontus
Better quantum gates are likely key to enabling fault-tolerant, useful quantum computers. This thesis compares gate optimization techniques by simulating single-qubit and two-qubit gates for superconducting qubits. The primary focus is deep reinforcement learning. For single-qubit gates, the task is to optimize a π-pulse, while for two-qubit gates, the task is to optimize the Controlled-Z gate. The results indicate that using an ansatz for the gate’s pulse shape can enhance the performance of deep reinforcement learning, both for single-qubit and two-qubit gates, but only significantly for single-qubit gates. A simple square-pulse ansatz approximately halves the simulation time needed to reach the coherence limit for the single-qubit gate studied. The speed-up in simulation should translate to a speed-up in experiments as well. The thesis does not find evidence that the implemented deep reinforcement learning algorithm yields better quantum gates than a state-of-the-art black-box optimizer, despite the black-box optimizer being easier to implement experimentally. For a quantum gate defined by piece-wise constant controls, a low-pass filter seems to enhance the performance, at least if the filter is considered when optimizing. This indicates that piece-wise constant controls, for example, generated with deep reinforcement learning, are not hindered by the limited bandwidth of control electronics. Finally, the study highlights the importance of ZZ coupling to understanding Controlled-Z gates.