Search Results (97)

The Erlang B equation is directly applicable to smaller hospital departments such as maternity and paediatrics departments. The bed occupancy margin is directly linked to size and not ‘efficiency’. A figure of 0.1% turn-away has been recommended as a planning target, i.e., only 1 in a thousand admissions suffer a delay before a bed can be found. Two bed calculators are provided which can be used for paediatric, obstetric, maternity, midwife-led, birthing wards and neonatal/paediatric critical care capacity. The negative effects of turn-away are likely to be context specific, hence, critical care > theatres > birthing unit > maternity unit. The uncertainty regarding future births is discussed along with the variable nature of seasonality in births. For paediatrics, much of bed demand is also influenced by the trend in births. Weighted population density (WPD) is associated with the size distribution of hospitals/units within countries and regions. This influences the average cost per birth/admission. The USA has a low WPD and a significant problem with small hospitals/departments. Only 10% of countries have WPD higher than England. Some countries choose to operate with even more hospitals than needed and this acts to elevate costs. Suggestions are made for a pragmatic approach to bed planning, especially where a dispersed population dictates a need for small hospitals, and hence, issues regarding size and costs. For maternity/paediatrics admissions (and other relatively short-stay admissions) the majority of overhead/indirect costs and most staffing costs should be apportioned based on admissions, and not LOS. Apportionment based on LOS creates the spurious illusion that LOS is the major cost driver and that reducing LOS will immediately save costs. Below 20 beds, Poisson statistical variation plus environment-induced randomness in daily arrivals imply that staff costs may become increasingly fixed irrespective of LOS. Around >30 beds, it looks possible to save costs by reducing LOS. Allocating total organizational costs to individual units and then to patients is less precise than realized and can be done in different ways, which all heavily rely on the steady-state assumption. When bed availability is the bottleneck, then reducing LOS may increase throughput per bed and increase income; however, is this for the benefit of the patient or for the benefit of the organization, and does it lead to higher unanticipated total costs including patient harm? The older economy-of-scale literature has been demonstrated to be flawed, with a recent focus on economy of scale at the department level being entirely consistent with the application of the Erlang B equation. A list of nine catastrophic pitfalls is given for doctors to identify dubious capacity advice from managers and external experts. Full article

With the in-depth advancement of the “dual carbon” strategy, Proton Exchange Membrane Fuel Cells (PEMFCs), as efficient and clean energy conversion devices, show great potential in the fields of transportation power and stationary power generation. For multi-stack fuel cell systems, a hierarchical optimization strategy based on Pareto decoupling and real-time correction is presented to achieve system efficiency improvement and balanced management of stack aging. Firstly, the Forgetting Factor Recursive Least Square (FFRLS) method is adopted to online identify the parameters of the system’s net output power-efficiency curve. Furthermore, in the steady-state layer, the Arithmetic Optimization Algorithm (AOA) is used to construct an efficiency-optimal candidate solution set. The Dijkstra algorithm is combined to search for the optimal power gradient path, generating a reference power table. In the dynamic layer, with the reference power table as the basis, the AOA algorithm is used to take efficiency optimization as the goal. Load fluctuations are suppressed in real time through strong constraints, realizing the balance between dynamic efficiency and operational stability. This method ensures the stable operation of the system and significantly improves the overall economy and adaptability of power allocation. Simulation results show that this strategy can effectively improve the overall operating efficiency of the system, slow down the stack aging rate, and ensure the stable operation of the system. Full article

Addressing the challenges of fluctuating renewable energy integration and stable green ammonia production, this study develops and optimizes a deeply integrated system comprising Solid Oxide Electrolysis Cells (SOEC), Liquid Air Energy Storage (LAES), Air Separation Units (ASU), and Haber–Bosch (HB) synthesis. We constructed a simulation model in Aspen Plus incorporating Ru/C catalyst kinetic parameters to analyze key subsystem parameters and optimize operating conditions based on maximized economy and efficiency. At the integrated system level, a parametric analysis of ammonia condensation temperature was further conducted to investigate the coupling characteristics. Using real power output data from Inner Mongolia, we formulated a dynamic energy scheduling strategy satisfying 24-h self-balancing constraints. Results indicate that a system producing 1415 tons of ammonia per day achieves a maximum hourly integrated profit of 69,838 CNY under optimal conditions: a hydrogen-to-nitrogen ratio of 2.98:1, operating pressure of 169 bar, reactor inlet temperature of 380 °C, and ammonia condensation temperature of −9 °C. Increasing the LAES throttle valve outlet pressure from 1 bar to 9 bar improved round-trip efficiency from 52.65% to 72.18%. The integrated-level parametric analysis reveals that the specific electricity consumption per unit mass of ammonia exhibits a non-monotonic trend with a minimum of 8.67 kWh/kg at −10 °C, reflecting the trade-off between refrigeration power consumption and cold energy recovery. In dynamic scheduling scenarios, the system maintains a maximum constant load of 45.78 MW with a steady-state liquid ammonia output of 6543 kg/h. This work optimizes both economic performance and system stability, providing a significant reference for the large-scale development of green ammonia systems. Full article

In addressing the challenges of strong power generation fluctuation, complex load variation, and dynamic topology changes in microgrid operation, this paper puts forward a proposal for optimal control methodology for distributed generation based on multi-agent adaptive decision-making. The initial conception of the dynamic strategy optimization module is to facilitate online learning and continuous optimization of agent decision-making capabilities. This objective is realized through the construction of a topology correlation matrix, which is based on microgrid operation data. The subsequent generation of preliminary control actions is facilitated by a multi-agent adaptive decision network. Concurrently, a safety optimization model founded upon the barrier Lyapunov function has been developed. The model has been designed to facilitate collaborative correction and safety constraint verification of the preliminary actions, thereby producing final control actions that satisfy global optimization and safe operation requirements. On this basis, an enhanced execution control module is employed, incorporating adaptive ramp rate limitations to calculate the target power reference, achieving high precision and fast tracking of power commands. The findings from both simulation and experimental studies demonstrate that, in complex scenarios such as load fluctuations and topology reconfiguration, the proposed method maintains voltage fluctuations within 1.6 V, achieves frequency recovery within 0.01 s, ensures a rapid power sharing response with a small steady-state error, and improves system operational economy by approximately 8.2% compared to conventional distributed control methods. This enhancement of dynamic adaptability, operational safety, and economic performance of the microgrid is therefore significant. Full article

The sustainable renovation of ageing industrial buildings presents both a challenge and an opportunity to enhance energy efficiency while preserving architectural and structural integrity. This study develops an integrated methodological framework for assessing and optimising multilayer wall systems in such conversions, combining thermal, environmental, and durability analyses. Six composite wall configurations were designed and numerically evaluated using steady-state 2D heat conduction and vapour-diffusion models. The results reveal substantial thermal improvement compared to the reference uninsulated brick wall (U = 1.41 W/m²·K). The proposed systems achieved U-values between 0.351 and 0.172 W/m²·K, meeting or surpassing European energy standards. The BP–EPS wall exhibited the lowest U-value (0.172 W/m²·K), while the FC–EPSR configuration achieved superior corner performance with a 2D surface temperature (Tsi) of 17.99 °C and the highest surface temperature factor (fRsi = 0.943), along with a reduced condensation risk, indicating more balanced overall performance. Weight and thickness reductions of up to 80.5% and 52%, respectively, were observed, enhancing retrofit feasibility and space efficiency. Life Cycle Assessment results indicated that optimised wall configurations reduced embodied carbon (A1–A3) by up to 78% and total life cycle emissions (A1–A3 + B6) by over 86% relative to the reference case. Vapour-diffusion analysis confirmed the FC–EPSR wall’s lowest condensation fraction, indicating excellent hygrothermal durability. Multi-criteria evaluation using the simple additive weighting method and Monte Carlo robustness analysis verified FC–EPSR as the most balanced and reliable system. Overall, the findings present a validated and replicable pathway for the sustainable renovation of industrial buildings, supporting the goals of European carbon neutrality and the circular economy. Full article

This paper examines economic and institutional convergence between EU Core, EU New, and Western Balkan countries over the period 2004–2023 using a comprehensive panel dataset and multiple convergence frameworks. Evidence of absolute β-convergence is found, although at a slow pace, while conditional specifications show that structural and institutional factors explain growth differences; institutional quality appears to affect growth primarily through direct effects rather than through significant interaction-based β-convergence. A Principal Component Analysis-based Institutional Index (PC1) explains 90% of the variance in institutional quality, highlighting its role in shaping cross-country growth differentials rather than directly influencing convergence speed. Group-specific models reveal heterogeneous convergence paths across European regions. EU Core economies exhibit relatively stable convergence patterns, reflecting their proximity to steady-state income levels. In contrast, EU New and Cohesion Economies do not display statistically significant β-convergence, suggesting that catch-up processes are uneven and not uniformly driven by initial income differences. Western Balkan economies show weak and limited convergence patterns, reflecting persistent structural and institutional constraints. Robustness tests (FE/RE, Hausman, VIF, Breusch–Pagan, residual diagnostics) confirm the validity of the results. Findings suggest an important role of institutional quality in supporting long-term growth and the accession process of the Western Balkans. Policy implications highlight the importance of governance reforms, human capital development, and EU integration mechanisms in accelerating convergence. Full article

New quality productive forces are increasingly recognized as important drivers of coordinated regional development, with urban agglomerations acting as key vehicles for their spatial implementation. Based on the theory of new quality productive forces, this study takes the 13 cities in the Beijing–Tianjin–Hebei (BTH) urban agglomeration as its research subjects, spanning the period from 2005 to 2023, and constructs a four-dimensional evaluation index system for new quality productive forces covering economic, social, ecological, and technological dimensions. It employs the entropy method to determine indicator weights and calculate development indices for each dimension and utilizes a coupling coordination model to measure the overall and subsystem-level coordination by analyzing their spatiotemporal evolution characteristics. The results indicate a steady upward trend in the overall coordination level, progressing from a low level to an intermediate level, with the state of coordination continuously improving; spatial differentiation is significant, forming a gradient development pattern centered on Beijing, with marked disparities in coordination levels among cities. Subsystem analysis reveals an imbalanced synergy structure: while economic and ecological synergy levels are relatively high, the coupling and synergy between science and technology and the economy and society remain prominent weaknesses. Most cities in Hebei Province lack sufficient scientific and technological innovation capabilities, resulting in a weak supportive role for economic and social development. Based on these findings, this study proposes policy recommendations such as establishing a regional innovation community, promoting the integration of factor markets, and strengthening collaborative governance of the ecological environment, with the aim of leveraging new quality productive forces to drive a qualitative leap in the coordinated development of the BTH urban agglomeration. Full article

Globalisation, accompanied by the rapid advancement of digital technologies, has become the bedrock of contemporary economies. However, the global digital divide has hindered many economies from enjoying the benefits of enhanced digitalisation. This study addresses the question: to what extent is there evidence of digital convergence or divergence among global economies, and what specific patterns of club clustering exist within the African continent? Employing a quantitative research design with secondary panel data from 123 countries (38 African), the study applies the Phillips and Sul convergence and club clustering algorithm to analyse digitalisation trends. The findings reveal that African countries exhibit significantly stronger within-club convergence dynamics than broader developing country groups, with Africa’s adjustment speed (σ = 2.5624) exceeding the Global South average (σ = 0.8394) by more than threefold. This indicates that African nations are following a similar ICT development trajectory and catching up with other global regions at an accelerated rate. However, the study identifies substantial digital inequality within Africa itself, as countries fail to converge to a single steady state, instead forming distinct convergence clubs. These results underscore that digitalisation follows a systematic and continuous process determined by both technological advancement and countries’ absorptive capacity to adopt these technologies. Full article

For decades, Saudi Arabia has relied heavily on oil revenues to support its economic growth. While this strategy brought substantial benefits, oil prices and global demand remain volatile, and oil itself is a non-renewable resource. These realities raise important concerns about long-term economic sustainability. In response, the country has pursued economic diversification to reduce risk and build a more resilient growth model. This study examines how the roles of the oil and non-oil sectors in driving GDP growth evolved between 1970 and 2024. To capture differences across economic conditions, the study applies both four and ten quantile regression models. These approaches allow us to observe how sectoral contributions change across low, moderate, and high growth periods. The results show that oil sector growth remains positive and significant across the distribution of GDP growth, with a stronger effect during periods of higher growth. At the same time, the non-oil sector is gaining importance, not only in stronger growth conditions, but is also cushioning the economy in periods of low growth. This signals gradual structural progress toward a more balanced and sustainable economy. The two-state Markov-switching model further identifies two persistent growth regimes: one more oil-dependent and another relatively more diversified. However, oil continues to play a meaningful role in both regimes. Overall, the findings suggest a gradual, steady transition rather than a sharp structural break. For long-term sustainability, Saudi Arabia needs to continue strengthening the productivity, resilience, and competitiveness of its non-oil sectors through its oil revenues accrued during periods of high growth. The implications of this study would be beneficial for all resource-rich economies aiming at economic diversification. Full article

Temperature and seepage are critical factors influencing the stability of unsaturated retaining walls, as they modulate soil shear strength through alterations in matric suction. This study proposes a three-dimensional analytical framework for evaluating active earth pressure under thermal and seepage conditions. With a kinematic upper-bound approach, temperature-dependent suction evolution and steady-state seepage are incorporated into a horn-shaped failure mechanism. The proposed method is validated against published analytical/numerical solutions, confirming its reliability. A systematic parametric study is conducted to examine how temperature, seepage velocity, wall geometry, and soil pore characteristics affect the active earth pressure behavior. The results reveal distinct behavioral trends depending on soil type: for sand, the active earth pressure increases with rising temperature, indicating reduced stability; conversely, for clay, it decreases with temperature elevation, suggesting enhanced stability. While seepage has minimal impact on sand, it exhibits a clear directional dependence in clays, with infiltration increasing active thrust and evaporation promoting stability through suction recovery. Three-dimensional analysis yields substantially lower earth pressure values compared with conventional two-dimensional approaches, highlighting potential design economies. The proposed method provides engineers with a practical tool for coupled thermal hydraulic mechanical analysis of retaining walls in unsaturated fills, facilitating more realistic and cost-effective designs under varying environmental conditions. Full article

This paper presents a conceptual and thermodynamic assessment of an innovative cogeneration system based on the aluminium–water reaction, designed to simultaneously produce hydrogen and electricity. The proposed layout integrates a liquid aluminium combustion chamber with a dual-stage heat recovery section and a steam turbine cycle, enabling the valorisation of industrial aluminium scraps within a circular-economy framework. A steady-state thermodynamic model was developed in Aspen Plus to evaluate system performance under different operating conditions, with a sensitivity analysis on key parameters such as the aluminium-to-water ratio (2.4–4), combustion efficiency, and steam generation cycle parameters. The system performance is investigated in terms of useful output (i.e., hydrogen and electricity production), including a simplified economic evaluation for the assessment of sustainability. Results indicate that, for equivalence ratios ensuring acceptable peak temperatures (≤1700 °C), the system can deliver 2–3 MW of electric power per kg/s of aluminium and achieve cogeneration efficiencies up to 83–87%, assuming a high conversion rate of water into hydrogen (roughly 0.106 kg of produced H₂ per kg of inlet Al, if 95% of mole conversion is considered). The minimum break-even levelized cost of hydrogen is estimated to be 15.7 EUR/kg under current economic conditions. Full article

Domestic and foreign capital and consumption goods are imperfect substitutes in production and demand functions of the growth model by Bardhan–Lewis. We extend the model by introducing exogenous technical progress and allow for foreign debt dynamics without dropping domestic capital goods. Trade and growth are mutually affecting each other. Trade may speed up or decrease growth in theory with and without technical progress in comparison with the Solow–Swan model. Steady-state growth rates include that of world income, and the income and price elasticities of export demand. The dynamic process of the economy is analyzed in terms of exports and foreign debt, and both as a share of a stock of imported capital goods. There are multiple steady states where imported capital goods are paid for by high exports and debt, low debt and low exports, or even negative debt and low exports. A stable VAR with data for Brazil shows that the high-debt steady state is relevant for this country. Steady states with high and low debt are saddle-point stable and the steady-state medium debt is stable. Neoclassical standard results appear as two special cases. We link the model to several strands of literature. Full article

Minimum wage is an important tool for reducing income inequality and supporting social welfare. Consequently, governments around the world have established minimum wage systems. As such, minimum wage policies connect distributive justice with the economy’s capacity to sustain broad-based welfare over time, placing the equity–efficiency trade-off at the center of societal sustainability. However, the micro-level impact of the minimum wage system on firms has always been an important topic for scholars. This study uses panel data from listed Chinese manufacturing firms over a period from 2005 to 2021 to construct an indicator of the minimum wage standards implemented in the firm locations. Employing the multiple linear regression model, this paper empirically examines the effects of minimum wage on labor productivity. The empirical findings demonstrate that minimum wage significantly reduced the sample firms’ labor productivity. Moreover, the negative impact of the minimum wage was primarily concentrated among non-state-owned firms, labor-intensive firms, firms operating in industries characterized by intense product market competition, firms situated in regions with strong legal protections, firms with comparatively low average employee wages, and export-oriented firms. Subsequently, this study delves into the mechanism through which minimum wage negatively affects labor productivity. We find that implementation of minimum wage leads to a reduction in corporate investment, indicating that there is no significant substitution relationship between capital and labor. These adjustment margins provide microfoundations through which statutory wage floors can influence the resilience and inclusiveness of development, indicating that the pace and design of wage increases should balance income protection with the preservation of productive capacity to support sustainable human development—grounded in steady productivity growth, equitable income distribution, and stable firm investment. Our findings contribute to a better understanding of the mechanism through which minimum wage affects labor productivity in theory, while concurrently furnishing policy insights for the optimization of the minimum wage system and maintaining sustainable societal development in practice. Full article

The world has fully entered the era of the intangible economy, in which intangible capital serves as the primary driver for achieving sustainable development. This paper employs a nonparametric dynamic distribution approach to analyze the short-term transitional patterns and long-term steady-state trends of intangible capital investment across 30 developed economies, shedding light on pathways for national sustainable development from the perspective of intangible capital. Meanwhile, this paper examines the impact of industrial structure, income structure, and external-demand dependence on intangible capital investment. The results show that (1) intangible capital investment exhibits persistence, and its long-term development shows signs of unconditional convergence; (2) the tertiary industry significantly promotes the development of intangible capital, highlighting the crucial role of industrial structure upgrading in fostering intangible-driven sustainability; (3) the development of intangible capital does not necessarily substitute for human capital or reduce the labor income share; and (4) extremely high reliance on the external market may hinder the growth of intangible capital. Full article

To address the fluctuation and instability of renewable power generation and the steady-state demands of chemical processes, a single-channel, non-isothermal computational fluid dynamics 3D model was developed. This model explicitly incorporates the coupling effects of electrochemical reactions, two-phase flow, and heat transfer. Subsequently, the influence of key operating parameters on proton exchange membrane water electrolyzer (PEMWE) system performance was investigated. The model accurately predicts the current–voltage polarization curve and has been validated against experimental data. Furthermore, the CFD model was employed to investigate the coupled effects of several key parameters—including operating temperature, cathode pressure, membrane thickness, porosity of the porous transport layer, and water inlet rate—on the overall electrolysis performance. Based on the numerical simulation results, the evolution of the ohmic polarization curve under temperature gradient, the block effect of bubble transport under high pressure, and the influence mechanism of the microstructure of the multi-space transport layer on gas–liquid, two-phase flow distribution are mainly discussed. Operational strategy analysis indicates that the high-efficiency mode (4.3–4.5 kWh/Nm³) is suitable for renewable energy consumption scenarios, while the economy mode (4.7 kWh/Nm³) reduces compression energy consumption by 23% through pressure–temperature synergistic optimization, achieving energy consumption alignment with green ammonia synthesis processes. This provides theoretical support for the optimization design and dynamic regulation of proton exchange membrane water electrolyzers. Full article