Demand for sand for construction and land-reclamation projects is increasing, while the long-term availability of suitable and accessible sand resources cannot be taken for granted (UNEP, 2022). Fine-grained dredged sediments may offer an alternative, but the dredging process often results in high water contents. These high water contents cause a longer duration of strength development and large settlements. Differences in particle settling velocity may also cause particle-size segregation during placement. Previous research suggests that these limitations do not necessarily exclude the use of dredged silt as reclamation fill (Smeenk, 2025). Mechanical dewatering before placement couldimprove the initial condition of the material and shorten the time required to form a usable deposit. This
study examines how the initial water content of dredged silt affects its segregation, density and strength development during and after placement in a land reclamation. The main research question is:

How does dewatering affect the segregation, density and strength development of
dredged silt used in land reclamations?

The research question is investigated through 18 settling-column experiments divided into four batches, each designed to examine a specific aspect of the placement process. Batch 1 establishes the reference behaviour by placing the sediment through an initial layer of water. Batch 2 repeats the placement without this water layer to determine how the available water column influences settling and segregation. Batch 3 uses a mixture with an increased fines content to examine the influence of the initial particle-size distribution. Batch 4 places the sediment in two consecutive layers to investigate whether the first deposit remains distinguishable or is disturbed by the second placement. Each batch includes initial dry-matter contents of 30%, 45% and 60%, while the reference and layered-placement experiments are performed in duplicate. The measurements describe the interface and bed-height development, vertical particle-size and density-related profiles, and penetration resistance. A one-dimensional numerical model is constructed and applied to each configuration to assess whether concentration-dependent settling formulations can reproduce the observed segregation (Te Slaa et al., 2015).

In the reference experiments, the final bed height decreases from approximately 26 cm at 30% initial dry-matter content to 24 cm and 21 cm at 45% and 60%, respectively. All deposits show vertical segregation, with coarser material accumulating near the bottom and finer material remaining in the upper sections. The 30% experiments show the strongest variation in 𝐷50, whereas the 60% experiments generally produce more gradual particle-size profiles. Increasing the fines content results in thicker beds, while the 60% experiment without an initial water layer produces the most uniform 𝐷50 profile of all experiments. A distinguishable boundary between consecutive placements is found in only one of the six layered experiments, indicating that the impact of the second placement generally remixed the first layer. Penetration depth decreases with increasing initial dry-matter content, indicating greater resistance after stronger dewatering. The adopted bearing-capacity interpretation gives indicative local strength values between approximately 640 and 975 Pa at the final penetration depths, although these do not represent direct measurements of undrained shear strength. The numerical model shows the best agreement with the reference experiments for 𝐷50 and with the increased-fines experiments for 𝐶𝑢, but does not consistently reproduce the measured profiles.

Overall, the results demonstrate that dewatering before placement can reduce segregation, decrease the volume of the deposit after settling and improve penetration resistance, although the magnitude of these effects also depends on the fines content, available water column and placement sequence.
The combined experimental and numerical approach contributes to assessing when mechanically dewatered dredged silt can be used as an alternative reclamation material and which aspects of its placement behaviour require further model development or soil improvement. ... Read more

Soft pneumatic leg actuators can generate planar motion from a single pressure input, but hysteresis makes their position depend on loading history. This thesis investigates whether measured pressure and mass flow can support real-time estimation of planar tip position and physical contact with the substrate, without embedded position or contact sensors.
An existing bistable dome actuator design was adapted and characterised. A structured pressure cycle uses jumps to initiate snap-through and reset. Flight time sets the scheduled return and approach phase, while contact time sets the phase intended to act against the substrate. A causal, data-driven observer combines a logistic floor-presence classifier with a pressure–flow release rule to activate and clear a substrate-mode gate. A position relation fitted by ridge regression maps filtered measurements, flow integrals and time since pressure events to tip position, with the gate selecting the substrate-conditioned contribution. Prescribed floor labels and synchronised camera coordinates supplied the classifier and position-fitting targets, respectively.
Independent validation covered 500 cycles and 29 combinations of scheduled flight and contact times from 1 to 10 s. Floor-presence classification achieved 92.8% accuracy and an F-score of 0.932. Position root mean square errors, with equal weight per cycle, were 3.356 mm horizontally and 1.477 mm vertically. At the tested flight times of 2–10 s and contact times of 1–10 s, classification accuracy was 99.5% across 420 cycles. At a flight time of 1 s paired with contact times of 1–3 s, it fell to 57.5% across 80 cycles.
The results support pneumatic observation for one actuator specimen, substrate height and pressure-cycle family, providing a basis for future feedback control of soft robotic legs. ... Read more

Metro systems in megacities such as Beijing and Tokyo face substantial differences in passenger demand between peak and off-peak periods. During peak periods, demand can exceed train capacity, causing denied boardings and long waiting times, while capacity is underutilized off-peak. Since metro systems often operate close to their maximum capacity, expanding infrastructure through additional tunnels is costly and time-consuming. Therefore, demand-management measures can provide an alternative to supply-side expansion.

This thesis integrates a supply-side measure, timetable optimization, with a demand-side measure, time-dependent pre-peak discounts. These measures should be optimized jointly, because pricing changes the temporal distribution of passenger demand and therefore affects the optimal timetable. The study investigates whether integrated timetabling and pre-peak discounts can redistribute demand across the morning peak and improve the utilization of existing metro capacity. The main research question is how integrated train timetabling and time-dependent pricing can be formulated and solved to minimize passenger waiting times at the network level.

To answer the research question, we develop a mixed-integer nonlinear programming (MINLP) model in which train headways and fare discounts are decision variables. The model links train departures to pricing stages and represents passenger demand shifts through elasticity parameters. It incorporates time-dependent pricing, train movements, and passenger flows through the network, including waiting, boarding, in-vehicle travel, transfers, and alighting. Oversaturated conditions resulting from limited train capacity are also modeled. The objective minimizes passenger waiting time, including waiting for newly arriving and transferring passengers, stranded passengers caused by capacity constraints, and a penalty for passengers remaining unserved at the end of the study period.

For small instances, the MINLP can be solved directly with Gurobi, but computation times increase rapidly with problem size. Therefore, a decomposition framework and hybrid matheuristic combining Adaptive Large Neighborhood Search (ALNS) with Gurobi are developed. The model is decomposed into a network-level train timetabling subproblem and a time-dependent pricing subproblem with integrated passenger assignment. ALNS searches for promising timetables using tailored destroy and repair operators, while the resulting pricing subproblem is linearized into a mixed-integer linear programming (MILP) model and solved exactly with Gurobi.

The algorithm is evaluated on synthetic instances using Gurobi as a benchmark. The matheuristic obtains comparable solutions while substantially reducing computation time for larger instances. For the largest instance, it reaches a solution within 0.1% of the best Gurobi solution after approximately 550 seconds, compared with 6,565 seconds for Gurobi. However, both solutions have an optimality gap of around 14%, limiting conclusions about solution quality. Overall, the matheuristic clearly improves computational efficiency, while ALNS converges faster than standard LNS.

The approach is applied to the central Beijing metro network, consisting of six bidirectional lines, 87 stations, and eight transfer stations during the morning peak. Four scenarios are compared: the initial timetable without pricing, the initial timetable with pricing, an optimized timetable without pricing, and joint optimization. Pricing alone reduces the objective by 1.65%, timetable optimization by 12.06%, and joint optimization by 13.61%. The joint pricing policy offers a 60% discount from 06:30–07:00, with approximately 3.8% revenue loss. Pricing mainly reduces stranded passengers, decreasing them from 26,024 to 20,677 compared with timetable optimization alone. Joint optimization also improves the objective by 0.32% compared with sequential optimization.

The results are subject to limitations, including headway-dependent demand, homogeneous price elasticities, fixed passenger routes, and predefined pricing stages. Nevertheless, the study demonstrates that integrated timetable and fare optimization is computationally feasible and offers a promising strategy for managing capacity-constrained metro networks. ... Read more

Stiffened composite panels are a lightweight, high stiffness-to-weight structural concept widely used in modern airframes, but the designs returned by structural optimization are rarely manufacturable. Free-size optimization produces a continuous, per-angle thickness field with jagged boundaries and sub-scale features that no Automated Fiber Placement (AFP) machine can lay down, and closing that gap is normally left to manual reinterpretation of the optimized result. This thesis therefore develops an integrated optimization and design-for-manufacturing framework that, within a single automated workflow, takes a stiffened composite panel from an arbitrary initial stiffener layout on a flat skin to an optimized stiffener layout on a blended, manufacturable variable-thickness laminate, and quantifies the structural cost of making that design manufacturable.

The stiffener layout is optimized explicitly using the Moving Morphable Components method in a Python-OptiStruct loop, after which the skin is sized by free-size optimization based on the converged layout, which returns a homogenized skin definition, a continuous total thickness and fiber-angle percentages per element, but no lay-up. This thickness field is made manufacturable in three stages: clustering into discrete thickness zones, a stacking sequence table parametrization that builds a guide laminate from the free-size lamination parameters and drops plies in an importance-driven order subject to the standard laminate and ply-drop guidelines, and a morphological filter that regularizes each fiber angle along its own direction at the AFP minimum cut length. A secant-based compensation step then returns the filtered design to its target material budget.

The framework is applied to an aircraft flat pressure bulkhead under uniform out-of-plane pressure, in-plane compression and asymmetric pressure, with the stiffener layout optimizer first verified against a reference configuration from the literature. Compared at equal volume, the final manufacturable designs improve on a uniform panel baseline by 15%, 18% and 7%, corresponding to structural knockdowns of 22%, 8% and 18% against the free-size theoretical optimum. The delivered designs therefore recover between roughly a third and three quarters of the performance benefit available from the optimization. The cost of manufacturability is not a fixed penalty: relative to the total available performance gain from optimization, it is smallest for the membrane-dominated compression case, whose stiffness depends on how much material is present rather than exactly where, and lar
... Read more

In this review article, two independently authored texts examine how modernist architecture on the African continent continues to shape and be reshaped by the operations that actively produce memory. The authors approach these operations in individual yet interconnected analyses of building ‘performance’, both a tool of colonial production and a practice of decolonial re-enchantment. The first text examines how modernist buildings, urban plans and infrastructures in West Africa created a narrow and technocratic definition of performance, focused mainly on European standards of climate comfort. Presented as bringing ‘civilised’ living standards to the continent, these interventions, equipped with sun shading, natural and mechanical ventilation, obscured the colonial and capitalist extractive practices that sustained not only European development in the 1960s but also the very same comfort. The second text counters this narrative by centring performance as an embodied, relational practice happening through and within architectural form. Looking at the life of the Uganda National Cultural Centre and Theatre, performance becomes a practice of reclaiming epistemic authority. The piece situates the struggles of reclamation within contemporary debates on preservation, where institutions often risk reinforcing a universalising heritage gaze that prioritises architectural form over lived experiences. Read together, both texts propose that decolonial futures emerge not by analysing and preserving architectural form alone but by interrogating the operations that produce memory and reclaiming performance as a situated, collective, and continuously negotiated practice. ... Read more