Search Results (3,113)

The underwater acoustic radiation of deepwater submersibles has become a growing concern in both academic and industrial communities. This study investigates the structure-acoustic coupling characteristics of a novel deepwater pressure hull, idealized as a triple spherical shell. A numerical model is established using a combined finite element and boundary element method to analyze the vibro-acoustic response of the target structure. The effects of three excitation types—unit sound excitation, unit force excitation, and their combined application—on the acoustic radiation of the intersecting spherical shells are systematically compared. Furthermore, the external sound power radiated by distributed acoustic excitations applied at different positions on each spherical shell is examined. Numerical examples are presented and discussed in detail, providing a useful technical reference for the quantitative acoustic design of underwater deepwater vehicles. The results show that the vibro-acoustic response of the triple spherical shell depends strongly on the excitation type and source position. For the selected unit inputs, the internal acoustic excitation produces a larger response than the local force excitation. After normalization to equal input power, the acoustic excitation produces a higher external radiated sound power than the force excitation in almost the entire frequency range. The radiated sound power is influenced by both the source–shell distance and the symmetry of the source position in the simulated cases. Full article

This study integrates institutional theory (INT) and the resource-based view (RBV) to investigate the mediating role of total quality management (TQM) in the relationship between environmental determinants (ED) and environmental performance (EP) in the Cameroonian manufacturing sector, an African emerging economy where sustainable manufacturing is increasingly important. Customer expectation (CE), policy and regulation (PR), and competitive pressure (CP) were identified as environmental drivers, TQM as the mediator, and environmental performance as the outcome variable in a proposed mediation model. Data were collected from 447 manufacturing personnel, including senior executives, middle managers, lower managers, and supervisors and analyzed using SmartPLS 4. The findings demonstrate that environmental performance is moderately associated with CE, PR, and CP. While CP has no relationship with TQM, CE and PR have a moderate influence. Additionally, TQM has a moderate relationship with environmental performance and plays a minor mediating role in the relationships between PR and environmental performance as well as between CE and environmental performance. TQM does not, however, act as a mediator in the relationship between CP and environmental performance. The findings establish TQM as an organizational capacity for linking specific environmental factors into environmental results. The study provides context-specific insights into how external institutional pressures can be translated into environmental performance in an African emerging economy by focusing on manufacturing firms in Cameroon. This broadens the scope of sustainability and quality-management research beyond primarily developed-country contexts. The study’s cross-sectional design and dependence on self-reported data from Cameroonian manufacturing companies may restrict the capacity to draw conclusions about causality and the applicability of the results to other industries and African economies. Full article

Background: Managing acute psychiatric crises remains a major challenge, as some situations exceed the capacity of even specialised care. These situations typically arise from a complex interplay of patient, team, ward and organisational factors, leading to prolonged admissions, increased use of coercive measures, and distress for both patients and professionals. Aims: This study aimed to identify the most challenging situations within High and Intensive Care wards, clarify their multifactorial origins, and explore strategies for more effective management. Method: This multi-centre, multi-method sequential qualitative study involved two phases: collecting 40 challenging cases, synthesized into two fictional vignettes, and discussing these in three focus groups with 33 mental health professionals, with data analysed through qualitative content and thematic analysis. Results: Participants recognised the vignettes and emphasised that it is the combination of patient, team, ward and system factors that places teams under sustained pressure, undermining the therapeutic environment and safety. These situations often evoke strong emotional responses and certain team dynamics, such as countertransference and splitting. Key challenges included dilemmas around admission, lack of treatment perspective, and systemic barriers. Suggested strategies focused on reward-based and autonomy-promoting care, requiring improved team communication, decisive clinical decision-making, and shared responsibility with external partners. Conclusions: Addressing challenging situations in High and Intensive Care wards calls for timely recognition, open discussion, structured team reflection, and ongoing staff training. Personalised care, clear protocols, and robust cross-sector collaboration are essential. Ongoing evaluation and further research, including patient and network partner perspectives, are needed to optimize interventions and ensure effective, empathic care. Full article

In coal-fired power plants, the coordinated control of boiler–turbine systems (BTSs) is required to track grid load dispatch instructions in real time while maintaining stable main steam pressure. Nevertheless, a BTS is affected by input constraints, external disturbances and model uncertainties, making it challenging for existing control schemes to stabilize the system within a fixed time. To tackle this issue, a fixed-time fractional-order sliding mode coordinated control (FTFOSMCC) strategy is put forward for the BTS. Firstly, a novel fixed-time fractional-order sliding mode disturbance observer (FTFOSMDO) is constructed by merging Riemann–Liouville fractional calculus with the fixed-time stability theory; the proposed observer is theoretically proven to drive the disturbance estimation error to zero within a fixed settling time that does not depend on the initial observation error. Secondly, the FTFOSMCC controller incorporates the Caputo fractional-order sliding surface, a novel variable exponential power reaching law, the state-of-the-art anti-windup technique, disturbance-observer-based feedforward compensation technique and fixed-time stability theorem, guaranteeing active suppression of actuator saturation and fixed-time stability of the closed-loop control system by Lyapunov’s theorem. Thirdly, simulations on a 300 MW subcritical BTS validate the exceptional tracking accuracy, disturbance rejection capability and robustness of the proposed strategy with the reduction of 33–90% in maximum tracking error, 12–98% in cumulative error, and 11–98% in time-weighted error compared to tuned PID and integer-order disturbance-observer-based sliding mode controllers. Full article

Portable radioactive aerosol monitoring systems integrate air sampling, aerosol collection, and radiation detection within a single measurement chain. In such systems, the aerodynamic conditions established during air transport through the collection filter may influence the spatial distribution of the sampled aerosol and therefore represent an important aspect of system characterization. The portable Monitoring Air pump for Radioactive Aerosol (MARE) system incorporates a high-flow air pump, an airflow monitoring unit, a pleated H13 HEPA aerosol collection filter, and a CeBr₃ scintillation detector for the continuous monitoring of airborne radioactive aerosols. In the present study, computational fluid dynamics (CFD) was employed to characterize the aerodynamic behaviour of the MARE air-sampling subsystem. Two complementary numerical models were developed using STAR-CCM+: a three-dimensional (3D) model representing the complete sampling configuration and a two-dimensional (2D) model representing a characteristic section of an individual filter pleat. The H13 HEPA filter was represented as a homogeneous porous medium using a Darcy–Forchheimer resistance formulation, thereby accounting for its macroscopic hydraulic resistance without explicitly resolving the underlying fibre-scale structure. The 3D model predicted a pressure drop of 268.7 Pa across the filter, while the corresponding 2D representative-pleat model yielded a pressure drop of 262.3 Pa. The resulting difference of approximately 2.4% indicates a consistent global hydraulic response between the two modelling approaches under the investigated operating condition. However, the 3D simulation revealed a pronounced spatial non-uniformity in the mass-flux distribution over the filter surface. The circumferential distribution was comparatively uniform at a given elevation, whereas the dominant variation occurred along the vertical direction, with higher mass flux predicted in the lower region of the filter, where the influence of the downstream suction system was strongest. At the individual-pleat scale, the mean mass flux was 1.36444 kg m⁻² s⁻¹. The internal region of the representative pleat exhibited mass-flux values approximately 30% above the mean, whereas the external region showed values approximately 10% below the mean, demonstrating substantial local redistribution of airflow within the pleated geometry. These results demonstrate that global pressure-drop measurements alone are insufficient to fully characterize the spatially resolved aerodynamic conditions within the sampling stage. CFD provides complementary information by resolving the local airflow distribution and identifying systematic flow non-uniformities that may be relevant to subsequent investigations of aerosol transport and deposition. The present results therefore provide an aerodynamic basis for future particle-transport and deposition studies aimed at establishing the relationship between local sampling conditions, aerosol collection, and the subsequent radiological response of the MARE system. Full article

Porter’s Five Forces remains a foundational framework in strategic management, but its application is often qualitative and can be difficult to compare across industries shaped by digitalization, network effects, and intangible capital. This study examines the K-Index (K) through a comparative review of published estimates of scale elasticity across five Japanese industries: automotive, printing, retail, financial services, and information services. K is treated as a quantitative indicator of latent competitive structure, particularly related to entry barriers and concentration pressure. The reviewed evidence shows that information services exhibit the strongest positive K values, ranging from 1.197 to 1.643, and that the automotive industry also shows a positive K value of 0.695. Metropolitan retail tends toward positive K, whereas printing, rural retail, and financial services remain in the non-positive-K category. These patterns suggest that K may complement Porter’s framework as an indicator for comparing competitive structures across industries. To be cautious, this review does not constitute an external empirical validation of K. The findings, including those about positive- and non-positive-K categories, should be interpreted as exploratory because the available evidence is limited to a small number of Japanese sectors. Further research should expand the sectoral and international scope and examine how changes in K are associated with observed competitive outcomes, such as concentration, pricing, entry, and innovation. Full article

Background: Young athletes in weight-category sports such as judo may experience pressure related to body weight, which can be associated with unhealthy eating. Building on two earlier studies of young Polish judo athletes, this study examined whether ways of coping with stress, weight-related pressure from the social environment, and perceived availability of nutritional support are associated with abnormal eating behaviours. Methods: In this cross-sectional study, 142 judo athletes aged 12–17 years (48 girls, 94 boys) completed questionnaires assessing eating behaviours (the Test of Eating Situation Style and the Three-Factor Eating Questionnaire), coping with stress (the How Do You Cope? inventory, JSR), and a study-specific questionnaire on weight-related pressure and perceived availability of nutritional support. Results: Girls reported higher emotion-focused coping in several sex-by-age subgroup comparisons. After accounting for sex, age, and BMI-for-age z-score, coping styles and weight-related pressure were significantly associated with dietary restraint and emotional eating. Critical comments about an athlete’s weight or body shape and pressure to maintain a specific competition weight were among the most consistent the strongest predictors, whereas BMI-for-age z-score was not. Athletes who perceived broadly defined nutritional support as available reported less eating in response to external cues than those without such support. Conclusions: In this sample of young Polish judo athletes, weight-related comments and pressure, together with coping strategies, are associated with abnormal eating behaviours. Careful coach communication about weight, evaluation of structured nutritional-support provision, and coping-skills training are candidate prevention targets that should be tested in longitudinal and intervention studies. Full article

The use of propylene (C₃H₆) in semiconductor manufacturing processes is increasing, and conventional 47 L cylinder supply systems are recognized as a primary source of leakage accidents associated with human error due to the need for frequent manual cylinder replacement. In this study, a Computational Fluid Dynamics (CFD)-based dispersion analysis and a preliminary accident consequence assessment—based on explicitly stated assumptions—were conducted for a gas cabinet housing a 440 L Y-type propylene cylinder. The potential for Vapor Cloud Explosion (VCE) was analyzed using a TNT equivalence model that accounts for the internal volume of the semi-enclosed cabinet. Pressure Vessel Burst (PVB) was evaluated using the Brode–Baker–Tang approach, while the fireball resulting from a Boiling Liquid Expanding Vapor Explosion (BLEVE) was assessed using the EFFECTS software. Under emergency ventilation conditions, the steady-state volume of the flammable gas cloud exceeding the Lower Flammability Limit (LFL) was calculated to be 6.9 m³, representing less than 0.2% of the total indoor volume. The distance corresponding to an overpressure of 1 psi was estimated to be 12.0 m for PVB and 13.6 m for VCE. Additionally, assuming that the entire 185 kg inventory participates in fireball formation, the distance corresponding to a radiant heat flux of 5 kW/m² was calculated to be 104 m. However, this distance represents an upper bound solely with respect to the fraction of material participating in fireball formation and does not account for other input variables in the fireball model. The presented results represent a preliminary consequence analysis based on the specified assumptions. Some of the applied assumptions are conservative; for instance, a constant leak rate and complete participation of the stored inventory in fireball formation were assumed. Conversely, the neglect of liquid pool evaporation and the assumption that vessel rupture occurs at operating pressure are not conservative approaches. The analysis indicates that, while the consequences of overpressure are confined to the immediate vicinity of the gas cabinet, the extent of thermal radiation impact depends on whether accident scenarios initiated by external fires can be prevented. These findings provide consequence-based baseline data for the design of safety systems—such as emergency ventilation, gas detection, automatic shut-off, fire suppression, and protective structures—for facilities utilizing 440 L Y-type cylinders. However, these results alone do not determine whether the installation of such facilities is acceptable from a safety perspective. Full article

Traditional village built heritage conservation requires attention to both the preservation of heritage cores and their relationships with peripheral environments. Existing research has extensively examined heritage preservation, spatial change, and external development conditions, but these aspects are often studied separately, leaving core–periphery relationships insufficiently explored. This study adopts a core–periphery perspective to develop a diagnostic framework comprising core preservation (U), peripheral pressures and constraints (P), and peripheral support (S). The framework identifies U–P relational configurations (G) and diagnoses relational conditions using the Core–Periphery Relative Risk Index (RRI), with S assessed separately as complementary information. An empirical analysis combines multi-source spatial data and GIS-based multi-criteria decision analysis for all 22 nationally recognised traditional villages in Jiexiu, Shanxi Province, China, forming a complete county-level case set. The results reveal four U–P configurations. Villages with better-preserved cores may face higher peripheral pressure, while those under lower pressure may have poorly preserved cores. Relational conditions and peripheral support also vary among villages within the same configuration. The study operationalises a core–periphery perspective through a relational diagnostic approach to traditional village built heritage, revealing differences that preservation assessments alone may overlook. It provides an analytical basis for understanding conservation issues and development conditions in traditional villages. Full article

Fractional operators are used in biomedical balance laws to encode memory. However, the order of the fractional operator used in these models is not the same as the memory recovered from the patients. This review maps one hundred scientific articles from the Scopus and Web of Science databases from 2019 to 2026 in which fractional operators were used in biomedical applications. The articles are separated into three main communities: compartment fractional differential equations, fractional control, and tabular clinical machine learning. For each article, information regarding the fractional operator used, the biomedical plant it acted upon, the type of data used, whether the fractional order was identified, and whether a locked model would change the decision for the clinical application was collected. The results from well-posed Caputo systems, simulated glucose and intraocular-pressure controllers, and fractional physics-informed neural networks were standard results. New methodological pipelines that combined fractional operators with machine learning on public biomedical data tables yielded high area under the curve values and low pseudo-time residuals in predictions, but they have yet to prove whether they recover the fractional order from the biomedical subject’s biological clock. Clinical prediction using these models began only when there was a change in the locked model in an external cohort of biomedical subjects with a biological clock, not when the fractional model was plotted through the public biomedical data tables. Full article

This study examined how elite women’s rugby union players perceived their off-season recovery experiences. An exploratory cross-sectional survey was completed by 140 elite women’s rugby union players (M age = 25.80, SD = 4.16) that captured global perceived readiness to train, recovery strategies, contextual demands, and preferred off-season structure. Quantitative data were analyzed descriptively, while responses to open-ended questions were explored using reflexive thematic analysis. Players reported a range of sport- and non-sport related demands during the off-season, including injury management, physical preparation, financial pressures, education and professional development, and external employment. Players reported a preferred off-season duration of 5.19 weeks on average (range 4–10 weeks), incorporating three broad components: a complete break from rugby, remote or personal training, and reintegration into the rugby environment. Overall, the findings indicate that elite women’s perceptions of off-season recovery reflect both rugby-related demands and wider occupational, educational and personal circumstances. The findings provide athlete-informed considerations for the design of off-season structures and identify areas for future prospective research. Full article

Navy divers are essential personnel for the operations of the fleet, supporting underwater ship maintenance, deep-sea salvage, and special naval warfare. Their effectiveness, however, is limited by heat loss in conventional wetsuits. Traditional neoprene wetsuits progressively lose insulating performance at depth because the increasing hydrostatic pressure compresses the neoprene’s closed-cell foam structure. To solve this problem, we developed a series of segmented wetsuits (K-suits) built by enhancing a neoprene undercoat with external pockets containing composite material plates made of incompressible hollow microspheres embedded in silicone. The K-suits significantly outperformed traditional 7 mm neoprene suits in field tests. Herein, we report on improved composites. A combination of 30 elastomers and additives was evaluated using American Society for Testing and Materials (ASTM) methods, including thermal conductivity testing (C518-21), compression testing (D575-91), slow-rate penetration testing (F1306-21), and custom impact testing. The results showed that multiple material combinations improve insulation, compressive strength, and resistance to puncture. Among all tested options, Sylgard 527 (S-527) with embedded 3M K1 glass microsphere had the best thermal insulation performance. Furthermore, its high flexibility makes it well suited for use in multilayer K-suits. Full article

Industrial heat decarbonization is a key challenge for the energy transition, particularly in applications requiring high-temperature steam when industrial waste heat is unavailable. This study presents a thermodynamic and annual performance assessment of a steam-generating heat pump system using ambient air as the external low-temperature heat source. The system combines cascaded low- and medium-temperature heat pumps with a mechanical vapor recompression unit. Steady-state thermodynamic models, parameterized using assumptions consistent with representative commercial components, are used to evaluate the system under nominal and annual operating conditions. The annual assessment is applied to the continuous steam demand of a real paper-production facility under Mediterranean climatic conditions. A grid-supported photovoltaic and battery energy storage system is included as the electricity supply framework for characterizing the operation of the steam-generating heat pump under time-varying ambient and renewable-generation conditions. Under the adopted modeling assumptions, the system produces saturated steam at 5–25 bar with design COP values of 1.35–1.49. As steam pressure increases, mechanical vapor recompression becomes the dominant electricity-consuming stage, resulting in a moderate reduction in COP while decreasing the sensitivity of overall system performance to ambient temperature variations. Full-year simulations show that the operating COP exceeds the design-point value for the investigated location because ambient temperatures are generally more favorable than the nominal design condition. The results of the preliminary economic analysis performed for three PV-BESS configurations show that the economic feasibility strongly depends on the electricity purchase price. None of the studied configurations recovers its additional investment at 50 €/MWh, whereas discounted payback periods range from 6.9 to 16.5 years at 100 €/MWh and from 4.2 to 7.3 years at 150 €/MWh. As the integrated system has not been experimentally validated, the results should be interpreted as model-based estimates. Full article

This study presents the numerical design and optimization of a convergent–divergent nozzle integrated with a pulsed detonation combustor (PDC) operating under reduced outlet pressure conditions. The work builds upon an experimentally validated TRL 4 PDC with demonstrated vacuum operation, which provides realistic inlet boundary conditions for the nozzle simulations. The divergent section of the nozzle is generated using the Method of Characteristics (MOC), while the overall geometry is subsequently optimized using a parametric process aimed at enhancing thrust and specific impulse while minimizing nozzle length, thereby reducing the overall size and mass of the propulsion system. Axisymmetric numerical simulations are performed to evaluate nozzle performance at an imposed external pressure of $100\mathrm{Pa}$, corresponding to the low-vacuum laboratory conditions of the preceding experimental campaign. The CFD results predict that an appropriately designed and compact nozzle significantly improves propulsive performance relative to the baseline configuration without a nozzle, increasing thrust output from 4.4 N to 5.94 N cycle-averaged with 16.5 N peak thrust. By combining MOC-based contour generation, numerical optimization, and unsteady CFD, the present work provides a computationally assessed nozzle geometry for subsequent manufacturing and experimental testing with the reference PDC. The optimized geometry obtained in this study provides a computational basis for subsequent experimental investigation. Full article

Anacamptis coriophora is a threatened tuberous orchid of the Irano-Turanian calcareous grasslands, subject to unsustainable harvesting for salep, increasing pressure from habitat loss and climate change. Asymbiotic in vitro culture is the principal method for its ex situ propagation; however, nitrogen nutrition, which is a decisive determinant of early morphogenesis, remains poorly optimized for Iranian terrestrial orchids, whose dust-like, endosperm-free seeds require external nutritional support for germination. Using a modified Malmgren basal medium, we investigated how nitrogen form and concentration affected asymbiotic seed germination and early seedling development in A. coriophora. Organic nitrogen (Aminoven at 25%, 50%, and 75% of full strength) was supplied in combination with inorganic nitrogen (KNO₃ and (NH₄)₂SO₄ in four combinations (balanced-low, nitrate-dominant, ammonium-dominant and high-inorganic). Germination declined markedly from 66% under balanced-low treatment to 13% under high inorganic nitrogen treatment, whereas organic nitrogen consistently enhanced germination across all inorganic backgrounds. Increasing Aminoven significantly promoted shoot elongation and biomass accumulation under low and moderate inorganic nitrogen levels but had little effect under high inorganic nitrogen concentrations. Root growth was enhanced by organic nitrogen across all inorganic treatments, whereas plantlet diameter increased under ammonium-dominant conditions, a signature of stress-induced radial swelling rather than enhanced vigor. Under the optimal medium (75% organic nitrogen, with low inorganic nitrogen), germination rate, shoot length, root length and fresh biomass reached 72%, 12.2 mm, 6.4 mm, and 44 mg plantlet⁻¹, respectively. These findings provide a practical and scalable propagation protocol for this pharmaceutically and ecologically valuable Iranian orchid, thereby supporting conservation strategies aimed at mitigating salep overharvesting and environmental degradation. Full article