This study analyses visitor experience in Palaeolithic rock art caves through sentiment analysis applied to online reviews. A total of 4,709 opinions posted between 2017 and 2025 on Google Reviews are examined for four caves open to the public: El Castillo and Tito Bustillo (Spain), and Font-de-Gaume and Rouffignac (France), all of which are inscribed on the UNESCO World Heritage List. Using text mining techniques and lexical co-occurrence analysis, the main semantic and emotional axes structuring visitors' discourse are identified. The results show that the tourist experience is shaped by cultural mediation, the symbolic construction of rock art, and predominantly positive emotional evaluations associated with the exceptional nature of the resource. Organisational aspects appear as peripheral dimensions, suggesting a degree of social acceptance of conservation-related restrictions.
This paper analyses tourists’ reported main transport mode for intra-destination trips in Madeira using post-pandemic airport-exit survey data collected between 2021 and 2023. The analysis focuses on main-mode choice and does not reconstruct complete multimodal trip chains, transfer sequences or door-to-door Mobility as a Service journeys. A panel Mixed Logit model is estimated with mode-specific cost coefficients and error components that capture persistent correlation across repeated choices. The model is benchmarked against a standard Multinomial Logit specification. An extended panel model then allows travel-time sensitivity to vary normally across respondents. This extension substantially improves model fit: the standard deviation of the travel-time coefficient is strongly significant, and 98.73% of the estimated coefficient distribution has the expected negative sign. Travel time is a robust determinant of mode choice, whereas monetary cost sensitivity is most clearly identified for rented-car and taxi use.Values of Time derived from the fixed-time specification and retained as comparative benchmarks, range from approximately €12.6/h for public bus to €30.8/h for rented car. Under the preferred random-time specification, a 10% reduction in bus travel time increases the predicted bus share by 2.47 percentage points, while a 20% increase in rented-car generalised cost reduces the rented-car share by 4.29 points. The combined scenario produces the largest policy-relevant reallocation: bus share rises by 3.96 points and rented-car share falls by 5.68 points. Continuous sensitivity analysis confirms that the direction of these responses remains stable across a wider range of attribute changes, although their magnitude is nonlinear.The analysis concerns the reported main mode used for each trip rather than complete multimodal trip chains, transfer sequences or door-to-door Mobility-as-a-Service journeys. Within this scope, the findings provide a transparent basis for ex-ante transport-policy appraisal in island and tourism-dependent destinations, particularly for coordinated packages combining public-transport time improvements with calibrated rented-car demand-management measures.
Abstract This study evaluates concrete in which natural aggregates (NAs) are replaced by electric arc furnace (EAF) slag siderurgical aggregate (SA), with partial cement replacement by silica fume and reinforcement using steel and polypropylene fibers. Mechanical tests (compressive and flexural) at 7, 28, and 90 days and microstructural analyses (SEM/EDS) of the interfacial transition zone (ITZ) were conducted. Optimal mixes containing 8% silica fume and 0.6% fiber volume exhibited an average ITZ thickness reduction from 27.8 ± 3.2 μ m (control) to 15.4 ± 2.1 μ m ( n = 20 fields), and compressive strength gains of up to 21% at 28 days (and up to 30% at 90 days for SA-C-100 mixes). Statistical significance was assessed using one-way ANOVA. These results demonstrate the synergistic effect of SA, silica fume, and fibers on densifying the ITZ and improving flexural toughness, and provide practical recommendations for mass concrete applications.
The adsorption behavior of trivalent europium cations (Eu3+) onto 2:1 trioctahedral clay minerals, including high-charge micas, was investigated to determine the mechanisms governing their retention in aqueous media. Eu3+ adsorption onto two additional smectites-a natural montmorillonite and a synthetic saponite-was also evaluated. Eu3+ incorporation occurs predominantly through interlayer cation exchange, producing a significant expansion of the basal spacing in montmorillonite and Na-2-mica, due to the strong hydration energy of the trivalent ion. In contrast, the highly attractive forces between the layers in Na-4-mica prevented interlayer expansion. Trioctahedral saponite also exhibited a secondary adsorption process, complexation of Eu3+ with the edge hydroxyl groups, consistent with its high surface area. Equilibrium in Eu3+-clay systems was reached within 1 h for both di-and trioctahedral clay minerals, and adsorption is well described by a pseudo-second-order kinetic model, indicating chemisorption as the rate-limiting step. At higher concentrations (> 180 mg & sdot;L-1) and longer contact times, a desorption stage was observed in montmorillonite, associated with cation redistribution toward lower-energy sites or Eu3+ complexation. Adsorption isotherms for all Eu3+-clay systems were adequately fitted by the Langmuir model, confirming the adsorption dominance of equally-energy sites. The maximum adsorption capacities (qm) followed the order Na-4-mica > Na-2-mica > saponite > montmorillonite, reflecting their abundance of accessible negatively charged sites. Photoluminescence spectroscopy confirms that Eu3+ occupies well-defined local environments, adopting a predominant configuration of outer-sphere complexes in the dioctahedral clay mineral, and of inner-sphere complexes in the high-charge micas. Correspondingly, Eu3+ lifetimes followed the decreasing order zsaponite > zNa-2-mica > zNa-4-mica > zmontmorillonite at maximum adsorption capacities. These findings demonstrated that the faster and strongly bonding adsorption of Eu3+ onto 2:1 clay minerals provides a promising approach for the retention and recovery of trivalent lanthanides from aqueous rare earth elements (REE) sources, without requiring prior pretreatment. The presented insights exhibit the high potential of dioctahedral and trioctahedral clay minerals, particularly Na-n-micas, as effective materials for REE recovery from secondary resources.
Open microchannels are a promising configuration for flow boiling because the top gap facilitates vapor evacuation and liquid replenishment, thereby improving thermal performance and moderating flow instabilities. However, their behavior under different inlet subcooling conditions remains insufficiently understood under hydrostatically controlled inlet-head operation, particularly when water is used as the working fluid. Deionized water flow boiling was experimentally investigated in an open microchannel heatsink featuring a 100 mu m top gap and microstructures with an aspect ratio of 15 and a length of 50 mm. Experiments were conducted at four prescribed hydrostatic heads (from 45 to 85 cm) at three different inlet temperatures: 60, 75 and 90 degrees C. Quantitative thermohydraulic measurements were complemented by high-speed flow visualization. Raising inlet temperature from 60 to 90 degrees C reduced the heat flux at the onset of nucleate boiling (ONB) by 73-79%, whereas the critical heat flux (CHF) decreased by only 19-34%. Consequently, the two-phase operating window widened and was largest at 90 degrees C. The lowest subcooling condition yielded the highest heat transfer performance, with maximum heat transfer coefficients of 12,847-23,686 W/m2 & sdot;K under surge-like vapor motion, but also the sharpest pre-CHF deterioration. This wider operating window incurred hydraulic and dynamic penalties: pressure drop increased by up to 335% from ONB to CHF and, at 102 W/cm2 under the highest hydrostatic-head condition, pressure drop oscillation severity increased by 169%. Increasing hydrostatic head from 45 to 85 cm more than doubled the ONB flow rate, whereas lower subcooling accelerated flow rate depletion and fluctuations toward CHF.
