Engineering

Abstract: This article explores the impact of weather and environment on shared bicycles. Using a random forest model combined with explanatory machine learning methods, the relationship, threshold effect, and interaction effect between weather factors and the transfer volume of shared bicycles at subway stations are analyzed; Research has shown that using the RF+IML method to study the impact of weather variables on shared bicycle transfer volume is feasible. There is a significant non-linear relationship between various weather factors and shared bicycle transfers. Temperature, humidity, and rainfall have specific activation and threshold effects on the number of shared bicycle transfers. When humidity is below 60%, the variation in transfer volume remains relatively stable; however, once it exceeds 60%, the transfer volume drops sharply. When the temperature exceeds 17 °C, its impact tends to reach saturation. Similarly, when rainfall reaches around 20 mm, its adverse effect also approaches the threshold. Temperature is the most important factor affecting the prediction of shared bicycle transfer volume, with temperature, cold weather, and cold forecasts contributing over 35% to the total effect. The interaction effect between temperature and other weather factors accounts for 22% of the total effect.During the long-term service of highway tunnel lighting systems, concurrent failures of multiple luminaires lead to severe deterioration of road surface illuminance distribution. Meanwhile, conventional periodic maintenance schemes suffer from significant time latency, failing to ensure driving safety during the maintenance latency period. To address this challenge, this study proposes a highway tunnel lighting quality optimization method based on luminous flux redistribution. First, based on the spatial geometric relationships of failed luminaires, multiple luminaire failure (MLF) scenarios are categorized into four typical topological structures: unilateral continuous failure (UCF), unilateral alternate failure (UAF), bilateral symmetric failure (BSF), and bilateral staggered failure (BStF). The degradation characteristics of average road surface illuminance and illuminance uniformity under each topology are quantitatively investigated. Second, with the optimization objectives of maximizing overall illuminance uniformity (U₀) and centerline longitudinal illuminance uniformity (U₁), a multi-dimensional optimization model is established. This model incorporates foundational constraints, including driving safety, physical dimming boundaries of luminaires, and road surface illuminance stability. Furthermore, to mitigate the transverse dark bands, lateral illuminance imbalance, and longitudinal fluctuations induced by MLF, four enhanced constraints are introduced: global minimum average illuminance, macroscopic regional symmetry, cross-sectional minimum illuminance, and longitudinal illuminance gradient limits. To efficiently solve this high-dimensional nonlinear optimization problem, a hybrid heuristic particle swarm optimization-differential evolution-simulated annealing (PSO-DE-SA) algorithm integrating PSO, DE, and SA mechanisms is developed. Finally, systematic experimental verifications are conducted across the four MLF topologies in a unidirectional three-lane tunnel scenario. The results demonstrate that for discrete failure scenarios supported by adjacent operational luminaires, the proposed method effectively mobilizes redundant luminous flux to achieve substantial restoration of lighting quality. Specifically, under UAF, the average road surface illuminance is restored to 153.46 lx, approaching the ideal non-failure state; under BStF, U₁ increases by 25.02%; under BSF, U₁ increases by 23.96%, effectively repairing transverse illuminance faults. However, under UCF involving three or more luminaires, the lighting system reaches its physical dimming compensation limit: the average road surface illuminance cannot be restored to the safety threshold, ensuring lighting quality only on the lane side with operational luminaires. This finding provides a quantitative criterion for determining the triggering threshold of preventive maintenance and luminaire replacement in tunnel operation and maintenance.

Abstract: Basalt is a promising geological medium for CO₂ storage because of its potential for permanent mineral trapping, although fluid–rock reactions can alter pore structure and hydraulic properties. This study investigates coupled axial deformation, hydraulic and geochemical evolution of basalt during CO₂-saturated brine flow at 88 °C and approximately 210 bar pore pressure. In situ axial deformation, differential pressure and apparent permeability were monitored continuously, while effluent chemistry, mineral saturation states and pore-structure properties were evaluated. Six axial deformation stages were identified, with a pronounced hydraulic transition after approximately 115 pore volumes (PV) injected. Larger deformation magnitudes coincided with decreasing differential pressure and increasing apparent permeability, and absolute axial strain change was positively correlated with stage-averaged apparent permeability (r = 0.919, R² = 0.8437). Absolute permeability increased from 2.41 to 8.55 mD, while measured porosity increased only slightly from 9.15% to 9.51%. Fe and SiO₂ concentrations generally increased during reactive flow, and late-stage saturation indices indicated thermodynamic favorability for selected secondary phases. Nitrogen adsorption measurements showed changes in accessible pore structure. These results demonstrate concurrent deformation, hydraulic and geochemical evolution and indicate that permeability evolution cannot be explained by changes in bulk porosity alone.

Abstract: This paper studies the stationary balancing of a full-scale bicycle robot using a scissored-pair control moment gyroscope (CMG). The test robot weighs 60 kg and includes two counter-rotating flywheels, a 20:1 geared gimbal system, an inertial measurement unit (IMU), and an embedded controller. For controller design, a simplified nonlinear model of the roll and CMG dynamics is derived and linearized around the upright position. The main contribution of this work is the experimental testing of a PDD2-LQR controller. This controller keeps the standard LQR state-feedback baseline and adds feedback from the roll error, roll rate, and filtered roll acceleration. Instead of redesigning the whole controller, the same LQR gains are used in both the baseline LQR and PDD2-LQR setups. This allows us to directly evaluate the benefit of the extra PDD2 terms on the same hardware under the same actuator limits. Experiments were carried out using PID, LQR, and PDD2-LQR controllers. The PDD2-LQR controller reached an average RMSE of 0.660 degrees and an average MAE of 0.477 degrees. These values represent improvements of about 51.8% and 43.2%, respectively, compared with the standard LQR controller. Overall, the results show that adding roll-motion feedback to the baseline controller significantly improves stationary balancing performance.

Abstract: Sensor failures, communication interruptions, and other monitoring problems can lead to missing acceleration responses in structural health monitoring of offshore platforms. To address this issue, a hierarchical feature fusion reconstruction (HFFR) method is proposed. The method employs multi-scale local morphology encoding to characterize local response morphology over different temporal neighborhoods, uses bidirectional temporal modeling to capture response evolution before and after the missing data, and adaptively weights temporal information according to feature correlation. A dataset is constructed using numerical simulation data from an offshore platform under different wave–current conditions, and the proposed method is evaluated through ablation and comparative experiments. After introducing multi-scale local morphology encoding and adaptive feature weighting into the bidirectional temporal modeling framework, the RMSE decreases from 0.5036 to 0.1109, while R² increases from 0.7581 to 0.9883, confirming the effectiveness of the hierarchical information representation framework. The results show that HFFR can recover the major peaks and valleys, amplitude envelopes, and local fluctuations of the missing responses, thereby improving both reconstruction accuracy and the preservation of dynamic response characteristics. The current validation is mainly based on high-fidelity numerical simulations; therefore, the applicability of the proposed method in real monitoring environments should be further verified through physical model tests.

Abstract: This study investigates how Digital Twins, photogrammetry, and related 3D technologies are transforming cultural heritage preservation, with a particular focus on Irish case studies. Heritage sites face increasing threats from climate change, conflict, natural decay, and limited conservation resources. Traditional methods-while culturally significant-struggle to meet modern preservation demands due to their cost, time requirements, and limited precision. Digital tools offer new solutions: photogrammetry enables accurate, low-cost 3D documentation; laser scanning provides high-precision structural data; and Digital Twins support predictive maintenance, environmental monitoring, and virtual engagement. Through a mixed-methods approach combining literature review, case studies, surveys, and interviews, the research evaluates four major Irish digital heritage initiatives: Beyond 2022, Spike Island, Ogham in 3D, and the Digital Repository of Ireland. Findings show strong benefits in documentation accuracy, asset management, and public accessibility, but also highlight barriers such as funding gaps, limited digital skills, and long-term data storage challenges. The study concludes that Ireland has significant potential for leadership in digital heritage but requires a coordinated national strategy to support training, infrastructure, ethical data management, and sustainable digital preservation practices.

Abstract: This article presents the findings of an experimental and numerical investigation into 120 mm thick concrete slabs subjected to impact by 7.62 × 51 mm projectiles with both hard (armour-piercing, AP) and soft (lead) cores. The results of laboratory tests, simplified calculations, and numerical simulations performed using ANSYS LS-DYNA software are presented. The material models and the numerical model description are provided. Experimental results demonstrated a substantial increase in both penetration depth and global specimen damage when subjected to the AP projectile. Despite its lower mass, the AP projectile caused significantly greater damage to the specimens than its lead-core counterpart. A comparison of the estimated penetration depths and the test results revealed that the projectile deformation upon impact must be accounted for when evaluating soft-core projectiles. Furthermore, it was observed that the elastic modulus had no influence on the impact resistance of the components.

Abstract: This work presents a soft finger designed, simulated, and experimentally tested, combining pneumatic actuation, variable stiffness, and embedded sensing. The finger integrates a fiber-reinforced pneumatic actuator that generates single-input underactuated bending through three interconnected chambers located at the MCP, PIP, and DIP finger joints. The design methodology follows bioinspired principles and cost-effective manufacturing constraints, producing a prototype via silicone casting with 3D-printed molds and incorporating a bio-based granular substrate for variable stiffness that allows post-deformation stiffening without compromising flexibility. Bending under pressurization is simulated utilizing the Finite Element Method (FEM) in ANSYS software, with the finger modeled using hyperelastic and fiber-composite material properties. Comparison of simulated and experimental results reveals an average deviation of approximately 8°. The adjustment of stiffness properties is achieved via vacuum-induced granular jamming, increasing the applied forces by up to 60% relative to the unstiffened state. An embedded sensing system (microphone) in the fingertip enables discrimination of contact surfaces based on captured vibration signals. These results indicate that finger deformation and stiffness can be controlled with minimal hardware and a simple design, supporting the use of this finger as a component in soft grippers or robotic hands.

Abstract: This paper reports a document-based, multiple-case study of six Internet-of-Things (IoT) prototypes designed and simulated during a one-week immersive course, “IoT for Data Intelligence,” delivered in July 2026 within the professional Master in Applied Artificial Intelligence (Maestría en Inteligencia Artificial Aplicada, MNA) at Tecnológico de Monterrey. Six teams followed the same five-day toolchain IoT theory; Oracle Application Express (APEX), SQL, and REST service design; MIT App Inventor; ESP32/Wokwi simulation; and generative-AI integration and produced Wokwi-simulated prototypes spanning industrial energy monitoring, agricultural hazard response, residential automation, cardiovascular telemonitoring, industrial waste reduction, and precision agriculture. A fixed coding framework was applied across architecture, AI-integration pattern, platform-level failure modes, security debt, and Sustainable Development Goal alignment, distinguishing findings that the course structure itself prescribes from findings the teams introduced independently. The six cases converged on a shared five-layer architecture and, in a pattern only partly prescribed by the course, on keeping generative AI in an advisory or fail-safe-wrapped role. Deposited results were also compared, for illustrative purposes only, against the course’s internal competency rubric. An observed proposal from a Pontifical Catholic University of Chile’s collaboration is discussed as an informal reference point rather than as evidence for generalization. This paper discusses the implications and limits of this small, single-institution, single-cohort, simulation-only case set.

Abstract: This work presents the functional enhancement of a previously developed miniature robot actuated by 3D-printed piezoelectric resonators through the integration of environmental and spatial sensors and the experimental comparison of proportional–derivative (PD) and sliding mode control (SMC) control strategies. The platform integrates an inertial measurement unit, a time-of-flight distance sensor, and a total volatile organic compound (TVOC) sensor, enabling the robot to execute a predefined route while acquiring environmental and spatial information. Two control strategies, PD and SMC, were experimentally compared using yaw-angle feedback and differential adjustment of the excitation frequencies. For a 0° reference, the PD and SMC controllers achieved mean absolute errors of 0.515° and 0.652°, respectively. During a transition from 0° to 90°, both controllers exhibited similar transient responses; however, during the return transition from 90° to 0°, only the PD controller successfully completed the rotation. In addition, the PD controller achieved a 12.27% higher linear velocity and a 5.44% higher counterclockwise angular velocity. The VL53L0X sensor exhibited a mean absolute error of 0.90 cm and a mean percentage error of 8.22%, while the SGP30 successfully detected the increase in TVOC caused by isopropyl alcohol, with relative differences ranging from 5.30% to 12.94% compared with a low-cost commercial air-quality monitor.

Abstract: Bond strength between a repair material and a concrete substrate is a principal parameter for assessing repair quality, most commonly evaluated by the semi-destructive pull-off test. Impact-echo (IE), a stress-wave based non-destructive method, is sensitive to interface quality, but the amplitude of characteristic frequency-domain peaks alone is statistically insufficient for reliable bond-strength estimation, motivating more advanced signal processing such as wavelet analysis. This paper presents a discrete wavelet transform (DWT) analysis of IE signals recorded on two groups of concrete repair systems differing in substrate class and surface-preparation technique. Statistical parameters of the detail-coefficient distributions - mean absolute deviation (MAD), standard deviation (SD), range (RG) - and detail energy (EN) were computed at the detail levels corresponding to the interface echo; finite-element simulations confirmed their sensitivity to interfacial voids. Multiple regression showed that detail-coefficient statistics and detail energy correlate with pull-off bond strength markedly better than frequency-peak amplitude, and that adding substrate roughness and near-surface tensile strength further improved the correlation. A multicollinearity and leave-one-out cross-validation analysis showed, however, that the amplitude-distribution statistics - mean absolute deviation, standard deviation and range - are severely collinear and do not validate as predictors at this sample size, whereas detail energy, and particularly the summed energy of details D2 and D3, is comparatively robust and yields the only model in this study that is both statistically significant and positively cross-validated. Regression equations are proposed accordingly, with detail energy identified as the recommended basis for bond-strength estimation. Discrete wavelet analysis - and specifically detail energy at the interface-echo pseudo-frequency - proves a useful and comparatively robust tool for evaluating bond quality and estimating repair-layer bond strength on concrete substrates.

Abstract: The increasing penetration of distributed energy resources (DERs) and new electric loads associated with decarbonization is pushing Distribution System Operators (DSOs) towards more proactive management of Medium Voltage (MV) and Low Voltage (LV) networks. In this context, short-term load forecasting (STLF) at the secondary substation (SS) level is becoming increasingly relevant for network operation and planning. However, conventional approaches typically use exclusively the data at SS level. without exploiting information available across the distribution network. This paper proposes a data-driven hierarchical forecasting framework that combines substation level predictions with aggregated forecasts of the underlying connection points. SS are characterized according to their operating conditions, based on the balance between annually consumed and produced energy, to investigate how these affect predictability. Forecasts from one to five days ahead are obtained using horizon-specific Random Forest (RF) models combining autoregressive, meteorological, and calendar information. Minimum Trace (MinT) reconciliation then ensures coherence between substation level and connection point forecasts. The analysis reveals markedly different forecasting behavior across operating conditions, with consumption-dominated substations proving considerably more predictable than their generation-dominated counterparts. Hierarchical reconciliation follows the same pattern, delivering its most consistent gains for passive substations, with an average day-ahead MAE reduction of 3.4%, reaching up to 6.4%, while its benefit gradually fades as local generation grows. The results provide DSOs with practical indications for adapting forecasting and reconciliation strategies across heterogeneous distribution networks.

Abstract: Hospital fire safety standards in Saudi Arabia remain primarily prescriptive and do not explicitly account for patient mobility constraints, complex building geometry, and time-dependent fire dynamics. The 2015 Jazan Hospital fire, which claimed 25 lives and injured more than 100 people, demonstrated that code compliance alone cannot guarantee occupant safety. This study presents a four-phase BIM framework integrating Autodesk Revit, PyroSim/FDS fire simulation, and Pathfinder agent-based evacuation simulation, applied to a 250-bed hospital in Qatif, Saudi Arabia. The FDS computational mesh was assessed at D*/δx = 12.2 against NIST NCSTAR 1-5E benchmark data (mean errors: temperature 6.8%, smoke optical density 7.2%), and Available Safe Egress Time (ASET) was determined using the multi-criterion ISO 13571:2012 methodology. Under the examined SBC 2018 baseline (Scenario 1, four corridor-end exits), smoke penetrated the ICU corridor within 60 seconds, yielding ASET = 118 s and a Monte Carlo Required Safe Egress Time (RSET) of 412 ± 35 s (n = 50; approximate 95% CI for the mean: 402–422 s), an ASET–RSET deficit of 294 seconds. Scenario 2, incorporating fire-rated ICU/OR compartmentation and ten distributed emergency exits, extended the reported ASET beyond 185 s and reduced mean RSET to 281 ± 22 s (approximate 95% CI for the mean: 275–287 s), a descriptive reduction of 32%. On the reported ASET range of 185–225 s, however, RSET remains greater than ASET; the residual deficit is 56–96 s. Sensitivity analysis across three ignition locations indicates that the Scenario 1 deficit is not specific to one fire origin. The findings support performance-based BIM simulation as a complement to prescriptive code assessment in hospitals.

Abstract: This article presents MIRAI-EDU-D, a software-free adaptive educational micro-robot designed to support tangible formative assessment in STEAM activities for primary and secondary education. The proposal addresses two current tensions: the expansion of educational robotics as a resource for active learning and computational thinking, and the need for school technologies that are transparent, repairable, inclusive and respectful of children’s privacy. Using an educational-technological design methodology, the system is specified through a discrete-electronics architecture composed of reflectance sensors, LM339 comparators, NE555 timers, CD4510 CMOS up/down counters, CD4028/CD4511 decoders and CD4000 logic gates. The robot reads binary cards placed by students, updates a physical memory of conceptual mastery and activates differentiated feedback: reinforcement, hint, remediation, advanced challenge or teacher alert. The design results show the alignment between electronic operation, formative assessment principles and STEAM competences by integrating science, technology, engineering, arts and mathematics in a manipulable learning experience. A validation protocol is also proposed, including pretest/posttest measures, observation rubrics, technical logs and teacher acceptance analysis. MIRAI-EDU-D is framed as a low-cost, auditable and privacy-preserving educational robotics alternative for schools with limited infrastructure, although classroom effectiveness must be tested through controlled pilot studies before making empirical claims about learning impact and long-term transfer outcomes.

Abstract: This article presents a qualitative engineering assessment of non-standard structural connections used in streetscape elements, including shelters, canopies, pergolas, recreational facilities, and other small-span structures. The analysed structures are made of steel, aluminium alloys, timber, and hybrid material systems. The need for individually designed connections arises primarily from specific functional and loading conditions, small member cross-sections, the use of hollow sections, restricted installation access, demanding architectural requirements, constraints associated with bending, hot-dip galvanising, and transportation, as well as the risk of galvanic corrosion. The research methodology comprises the identification of key design constraints, the analysis of selected case studies, and a comparative assessment of connection solutions in terms of structural performance, durability, constructability, maintainability, adaptability, demountability, and circularity. The solutions discussed include concealed connections within hollow sections, small-diameter and stainless-steel fasteners, locally reinforced joints, modular field splices, and electrically isolated interfaces between dissimilar metals. The findings indicate that appropriately designed non-standard connections can support durability, selective component replacement, upgrading, relocation, non-destructive disassembly, and the reuse of structural components. However, these benefits do not arise automatically from the customised nature of a connection, as additional material use, fabrication complexity, limited fastener accessibility, and degradation-sensitive interfaces may increase whole-life impacts. Structural connections should therefore be assessed as integral components influencing the performance of a structure throughout its service life rather than solely as local load-transfer details.

Abstract: This research focuses on our bidirectional Greedy pairing of the mechanical vibrations of a Hydra-Rib basketball rim and backboard, which had an National Collegiate Athletic Association (NCAA) and Fédération Internationale de Basketball (FIBA) mandated Energy Rebound Testing Device (ERTD) suspended from it. The Experimental Modal Analysis (EMA) used Brüel & Kjær vibration instrumentation to gather vibration data which was then processed by the Spectral Dynamics STAR7 package into mode-shapes and frequencies. A MECWAY Finite Element Analysis (FEA) analytical model of the basketball rim, backboard, and frame was created using hexahedral elements, and the ERTD which hung from the outer end of the basketball rim was modeled as a 3kg truss element. The EMA and FEA mode-shapes were then exported for processing by our GNU Octave programming, which employed a bidirectional Greedy selection algorithm to pair those EMA and FEA modes which most closely matched, to generate our Cross Application Modal Assurance Criterion (CrossMAC). This CrossMAC showed high values along its main-diagonal, showing good agreement between like mode-shapes, and low off-diagonal values, indicating desired orthogonality, and we achieved a Frequency MAPE of 23.3% and a Mode-Shape MAPE of 5.974%.

Abstract: Chiplet integration enables designers to assemble dies from multiple vendors and connect them through standardized interconnect protocols, such as universal chiplet interconnect express (UCIe). This multi-vendor model, however, redraws the trust boundary and exposes inter-chiplet links to hardware Trojan insertion. Yet this attack surface remains largely unexplored, especially in FPGA-based chiplet ecosystems. In this work, we present the first hardware Trojan that stealthily bypasses the cyclic redundancy check (CRC)-based integrity mechanism of the UCIe protocol. The Trojan deliberately flips data bits in ways that preserve the original checksum, allowing corrupted inter-chiplet traffic to pass CRC validation undetected. We model the Trojan in a multi-die FPGA AI inference engine and show that these evasive corruptions can induce targeted misclassification, including (i) input-class suppression, (ii) forced-class promotion, and (iii) conditional class redirection. The Trojan incurs an overhead ranging from 18–35 and flip-flops (FFs) ranging from 14–17 when implemented on a Kintex-7 FPGA. Our results expose a critical gap in UCIe’s integrity mechanism. Although CRC remains effective for random error detection, its linear structure enables protocol-aware Trojans to inject checksum-preserving corruptions. The integrity gap identified in our work motivates the need to move beyond error-detection codes to secure UCIe-based chiplet interconnects.

Abstract: Green hydrogen produced via water electrolysis using renewable energy is central to the energy transition, but high production costs remain a major barrier. Solar photovoltaic (PV) and wind farms are dominant renewable sources, yet each has drawbacks: PV is inexpensive but limited in operating hours, while wind is costlier but offers steadier output. This paper introduces the Combined Hydrogen and Power (CHyP) concept, a co-production configuration in which hydrogen and electricity are treated as primary products for an industrial off-taker within a hydrogen hub. The electrolyzer is sized from the generation duration curve to maximize annual hydrogen output and is operated at nominal load to limit failures and maintenance. The resulting surplus electricity is sold to a nearby end user, integrating electricity revenues as a cost offset in the LCOH. Simulations of 500 MW hybrid wind–photovoltaic plants across Spain identify an optimal wind share of 27%. Assuming a surplus electricity price of 60 €/MWh, minimum LCOH values range from 1.68 to 4.40 €/kg, with values below 2 €/kg in selected locations.

Abstract: Cadmium telluride (CdTe) is a direct-bandgap semiconductor with strong optical absorption and is therefore well suited to thin-film photovoltaic conversion. This study brings together the AFORS-HET modeling work on CdS/CdTe devices, the figures and material-parameter table, and supporting literature supplied with the project. The analysis focuses on three closely connected limitations: formation of a non-ohmic Schottky barrier at the metal back contact, use of a highly doped electron-reflector (ER) region to modify carrier transport near that contact, and surface recombination velocity as an effective model for pinhole- or defect-related losses. The simulations indicate that back-contact and interface conditions influence open-circuit voltage much more strongly than short-circuit current density. Optimized modeled structure using an ER, a doping concentration of 7 × 1018 cm^-3, an ER thickness of 100 nm, and an effective barrier height of approximately 0.1 eV reaches a simulated efficiency of 19.83%, with Voc = 917.6 mV and Jsc = 28.45 mA/cm². The surface-recombination study further shows that severe pinhole conditions can lower Voc to approximately 0.73 V. These results are interpreted together with literature on CdTe doping, interface engineering, minority-carrier lifetime, grain-boundary recombination, and Cu-related back-contact effects [1-7]. The combined picture emphasizes that high optical absorption alone is not sufficient: contact selectivity, interface quality, carrier lifetime, and defect control must be optimized simultaneously.

Abstract: Small fixed-wing unmanned aerial vehicles are almost always driven by exposed propellers, whose slipstream washes the airframe. This paper discloses an alternative in which a multi-bladed micro electric ducted fan is embedded in the centreline body of a delta wing, with a row of guide vanes behind the rotor and the exhaust discharged behind the airframe, so that no rotating component is exposed to the external flow. Two variants with 13-bladed, high-solidity rotors of 68 mm and 46 mm tip diameter, driven at 30,000 revolutions per minute by a 6300 KV motor, are defined and assessed by computational fluid dynamics against the same airframe fitted with an APC 10x7 puller propeller, after independent validation of the airframe and propeller models. At 10 degrees angle of attack both embedded variants produce a net propulsive force at their design speeds of 30 m/s and 10 m/s, and velocity vectors confirm that the guide vanes remove the rotor swirl. The 46 mm variant retains the lift coefficient of the clean wing, 0.574 against 0.570, while the larger 68 mm duct reduces it to 0.427 but raises the lift-to-drag ratio from 9.8 with the puller propeller to 10.4. A 3D-printed prototype of the engine was built and run, and its rotor was tested on a thrust stand.

Abstract: Shared micromobility can contribute to more sustainable urban mobility by improving access to urban opportunities without relying exclusively on private motorized transport, but the opportunities that can potentially be reached through the transport network may not coincide spatially with the availability of shared vehicles. This study proposes a data-driven microscopic accessibility framework to assess this relationship at the building level. Origin–destination Global Navigation Satellite System (GNSS) data from free-floating shared micromobility services are map-matched and routed over detailed urban networks to reconstruct plausible trips and derive mode-specific travel speeds. Potential Accessibility is then calculated for each building as the opportunities reachable within a 15-min travel-time threshold. A complementary Vehicle Supply indicator is derived from observed trip-end locations reachable within a 3-min walking-time threshold, and the two components are combined into Effective Accessibility. Their spatial correspondence is further assessed using Spearman rank correlation, high-value coverage, and a normalized dissimilarity index. The framework is applied to Bologna and Florence, Italy, considering bicycles, e-bikes, and e-scooters where available. The results demonstrate that network-based accessibility and shared-vehicle supply provide complementary information and should not be interpreted independently. The proposed framework enables localized identification of areas where high accessibility potential is insufficiently supported by the observed shared-mobility service and can support the planning of more sustainable shared-micromobility systems, while providing a basis for future dynamic accessibility analyses incorporating temporal dependency and fleet availability.