Search Results (51,954)

This study examines how ENSO episodes affect maize price volatility transmission between the United States and South Africa. Using daily price data, from 1997 to 2024, for U.S. corn and South African white and yellow maize futures, the study employs GARCH models augmented with ENSO phase indicators and the Southern Oscillation Index (SOI) to determine volatility spillovers. The results show that South African maize prices respond to lagged US corn prices and exchange rate fluctuations, with price volatility of both white and yellow maize prices being more persistent during El Niño and La Niña events. This study integrates climate variability indicators, specifically different ENSO phases and the SOI, to investigate climate-driven volatility transmission between developed and emerging markets. Significant results were obtained when the Southern Oscillation Index was added in the volatility equations. Not only does the inclusion of ENSO indicators and SOI enhance the explanatory power of GARCH models beyond existing studies, it also provides evidence of climate-driven volatility spillovers between a developed and developing market. These findings highlight the role of climate variability in agricultural market dynamics and stress the need for proactive risk management strategies such as buffer stocks and climate responsive financial instruments to ensure food security and market resilience in Southern Africa. Full article

This paper presents a new derivative-free method with a symmetric rank-one (SR1) update for handling constrained nonlinear systems of monotone equations. Distinctively, the approach employs a revised SR1 update formula that leverages information from the latest three iterates and their corresponding function values—a key improvement over existing SR1 variants relying only on two-point information. Derived from this revised formula, the approach integrates projection techniques for performance enhancement. One of its key advantages lies in the search direction: it exhibits sufficient descent and trust-region properties while eliminating the need for line search techniques. Theoretical analysis shows that the algorithm converges globally under specified conditions. Furthermore, numerical experiments are conducted to compare the proposed algorithm with two other existing approaches; results demonstrate that it exhibits superior reliability and robustness in terms of the number of iterations, function evaluations, and CPU runtime. Full article

Digital Twins provide comprehensive capabilities to solve critical logistics problems such as visibility, monitoring, optimization, prediction, and simulation. This study explores the existing DT readiness assessment models in SCs and logistics, discovers their limitations, and proposes a conceptual model based on an organization’s internal and external attributes to strategize DT implementation in logistic functions. The results showed that the existing readiness assessment models have weaknesses and drawbacks, motivating the researchers to develop a new logistic DT readiness assessment model. This study identified six main organizational dimensions directly affecting measuring overall logistics’ DT readiness, which are management readiness, personnel readiness, information readiness, organization readiness, product readiness, and process flow readiness. Their relationship is mediated by Technology Integration and moderated by Supply Chain Complexity, which was tested using partial least squares structural equation modeling to show the importance of strategizing DT implementation in logistics. Full article

Cage pocket beam deformation occurs due to susceptibility to impact loads under high-speed operating conditions and ultimately alters the bearing’s dynamic characteristics. Regarding the dynamics of localized cage deformation, rollers’ interactions, raceways, and a cage were incorporated, and a rigid–flexible coupled cylindrical roller bearing was modeled dynamically, considering localized cage deformation. The dynamic equations were solved using an adaptive variable-step BDF predictor–corrector algorithm to characterize the behavior of the bearing system. Localized deformations of the cage affected the dynamic characteristics of the bearing. The results show that the cage beams deformed, which increased the local clearance between rollers to a certain extent and was beneficial for the stability of roller motion. However, further increases in clearance can induce roller slippage, suggesting that changes in local clearance are the primary cause of roller slippage. Full article

Reservoir simulation remains a major computational bottleneck for production optimization, history matching, and uncertainty quantification, particularly as geological models become increasingly detailed and recovery processes more complex. Coarse-grid network (CGNet) models have recently emerged as an efficient, physics-grounded proxy to full-physics simulations by solving the flow equations on a coarse network whose parameters are freely calibrated to reproduce fine-scale or observed well responses. In this study, we investigate how different coarse-partitioning strategies affect the accuracy and robustness of CGNet models. Four partitioning approaches are examined: a simple cookie-cutter partition, and three partitions based on cell-wise indicators—absolute permeability, velocity magnitude, and the product of forward and backward time-of-flight. Two test cases are considered: one using a single layer of the SPE10 benchmark dataset and the other using a sector model from the Norne field. Results show that, despite substantial differences in coarse-grid topology, the four CGNet models achieve comparable convergence behavior and predictive accuracy. For the SPE10 case, all models reproduce the fine-scale responses well, and no clear superiority among the partitioning methods. In the Norne case, the time-of-flight–based partition yields the lowest misfit and slightly better well-response predictions, although overall differences remain modest. These findings demonstrate that CGNet models are robust to coarse-grid topology and that incorporating flow-based indicators in partition generation can offer marginal improvements for complex geological systems. The results highlight the potential of CGNet as a cost-effective, physically consistent surrogate for large-scale reservoir applications. Full article

This paper deals with a new coupled system of integro-differential equations involving the generalized proportional Caputo derivatives equipped with nonlocal four-point boundary conditions. Sufficient criteria for the existence and uniqueness of solutions for the studied system are derived based on Krasnoselskii’s and Banach fixed-point theorems, respectively. Applications are constructed with three different cases to illustrate the main results. Full article

Background: Population ageing is a global challenge, prompting ageing-in-place policies in Hong Kong to support community-dwelling older adults while reducing healthcare costs. Yet, their impact on health-related quality of life (HRQoL) remains underexplored amid Hong Kong’s long life expectancy and growing older population. Traditional surveys are costly and time-consuming, while routinely collected registration data offers a large, efficient source for health insights. This study uses enhanced administrative data to track HRQoL trajectories and inform policy. Methods: This is a prospective, open-ended longitudinal study, enrolling adults aged 50 or older from a collaborating non-governmental organization in Hong Kong’s Southern District. Data collection, started in February 2021, occurs annually via phone and face-to-face interviews by trained social workers and volunteers using a standardized questionnaire to assess individual (e.g., socio-demographics), environmental (e.g., social support via Lubben Social Network Scale-6), biological (e.g., chronic illnesses), functional (e.g., cognition via Montreal Cognitive Assessment), and HRQoL (e.g., EQ-5D-5L) factors. A secure online system links health and service use data (e.g., service utilization like community care visits). Analysis employs descriptive statistics, group comparisons, correlations, growth modelling to identify health trajectories, and structural equation modelling to test a revised quality-of-life framework. Sample size (projected 470–580 after two follow-ups from a 2321 baseline) is based on power calculations: 300–500 for latent class growth analysis (LCGA) class detection and 200–400 for structural equation modelling (SEM) fit (e.g., RMSEA < 0.06) at 80% power/α = 0.05, simulated via Monte Carlo with a 50–55% attrition. Discussion: This is the first longitudinal HRQoL study in Hong Kong using enhanced non-governmental organization (NGO) administrative data, integrating social–ecological and HRQoL models to predict trajectories (e.g., stable vs. declining mobility) and project care demands (e.g., increase in in-home care for frailty). Unlike prior cross-sectional or inpatient studies, it offers a scalable model for NGOs, informing ageing-in-place policy effectiveness and equitable geriatric care. Full article

This study investigates how urban park co-governance fosters a sense of belonging among residents and advances the Right to the City. It examines the role of parks in mitigating spatial fragmentation, inadequate living conditions, and relational disconnection in high-density urban environments. As essential green infrastructure, urban parks play a vital role in promoting spatial justice, community cohesion, and resident well-being. Drawing on Henri Lefebvre’s Right to the City framework, this study introduces the concept of the Right to Urban Park, conceptualised as a bundle of rights: freedom (appropriation), individualisation (socialisation), habitat and to inhabit (differentiation), and key point participation. Focusing on the governance and self-governance of parks in high-density cities, this research mixed qualitative and quantitative methods to analyse a representative case in central Shanghai. The findings show that participation, collective action, and co-governance in urban parks effectively support the Right to the City. Integrating the Right to Urban Park framework into park planning and management enhances diversity, equality, and inclusion, thereby improving urban well-being. This framework plays an important role in fostering enfranchisement, individuation, and association processes that strengthen recognition, sense of belonging, and well-being. Full article

This study determined the effectiveness of ozone and Fenton’s reagents, and the ozone delivery system, for the degradation of the persistent organic compound p-chlorocresol (4-chloro-3-methylphenol) in tannery wastewater. Laboratory trials demonstrated that removal of p-chlorocresol from wastewater at pH 4.1 using ozone was at least 70% within 2–3 h. Fenton’s reagent did improve the p-chlorocresol removal, but only by 10%. When we normalize the % removal data to account for reaction time and ozone dose, the degradation rates of p-chlorocresol in the ozone only and ozone plus Fenton’s treatments were similar, ~76 mg p-chlorocresol g⁻ O₃ h⁻¹. In the pilot trials, the addition of ozone via a venturi delivery system with improved circulation achieved up to 46% removal of the p-chlorocresol in wastewater at pH 4.1 within 24 h; this equated to a removal rate of 3.8 mg p-chlorocresol g⁻ O₃ h⁻¹. The large difference in removal rate between the pilot and lab trials was attributed to higher organic load in the wastewater. The addition of Fenton’s reagent increased the removal of the p-chlorocresol to 66% in the venturi injection trial and almost doubled the removal rate (6.7 mg chlorocresol g⁻ O₃ h⁻¹). The addition of ozone via a direct blower system was not as effective as the venturi system because of the large loss of ozone from the tank reactor. Full article

The paper focuses on fault diagnosis in nonlinear analog circuits, a topic that has been explored in the literature for over 50 years but remains unresolved due to its complex nature. It reviews various aspects of nonlinear circuit diagnosis, including methods for assessing testability, selecting diagnostic tests, and conducting diagnostic processes through simulation before and after test methods. The paper also discusses the use of artificial intelligence tools in this context. Given the specific characteristics of nonlinear circuits used as DC-DC converters and the wealth of the existing literature—including review papers on the subject—this issue is addressed only briefly. The main aim of the paper is to identify research challenges in fault diagnosis for a general class of nonlinear circuits. To illustrate and discuss these challenges, the paper provides examples, including ambiguity in diagnostic equation solutions, multiple equilibrium points, and the effects of self-heating. These examples can serve as simple benchmarks for new proposals to advance comprehensive diagnosis methods for nonlinear circuits. Full article

A crystal plasticity finite element model is developed and implemented to numerically study the deformation behavior of hexagonal close-packed metals using α-titanium as an example. The model takes into account micromechanical deformation mechanisms through dislocation slip along prismatic, basal, and first-order <c+a> pyramidal systems, as well as tensile twinning. Twin initiation follows a two-conditional criterion requiring that both the resolved shear stress in a twin system and the accumulated pyramidal slip simultaneously reach their critical values. Three-dimensional polycrystalline models are generated using the step-by-step packing method. The crystal plasticity constitutive model describing the deformation behavior of grains is integrated into the boundary-value problem of continuum mechanics, including dynamic governing equations. The three-dimensional problem is solved numerically using the finite element method. The micromechanical model is tested for an α-titanium single crystal along the [0001] direction and a polycrystal consisting of 50 grains. The numerical results reveal that twin propagation is controlled by the critical value of accumulated pyramidal slip, emphasizing the need for experimental calibration. The agreement between numerical and experimental results provides the model validation at the meso- and macroscales. Full article

The primary goal of the present study was to assess the efficacy of the inflation-targeting framework (ITF) within the Egyptian economy. This was achieved by scrutinizing the monetary policy framework (MPF) from 2005 to 2022 and measuring its effectiveness in realizing monetary policy objectives (MPs). The approach involved constructing a macroeconomic model that captures the interconnections among macroeconomic variables (real and monetary), whether they serve as targets or instruments of MP or are otherwise closely associated variables. The model also helps to estimate the sensitivity coefficients of macroeconomic variables (real and monetary) related to changes in interest rate, exchange rate, money supply, and real output and then to identify how the impact transfers between monetary variables and related macroeconomic variables, as well as the amount of that impact. Using a quarterly series constructed from the original annual data via a Bayesian temporal disaggregation procedure (2005Q1–2022Q4), our findings conclude that there is a mechanism in the Egyptian economy to transfer the impact to and from the basic macroeconomic variables (household and investment expenditure, net exports, money demand, interest rate, and real output). This reflects the responses of the household and business sectors in their decisions on changes in both the real interest rate and the level of output. However, the extent to which the impact of monetary policy instruments was transmitted to the main monetary target value (money supply) and subsequently to real output (or economic growth) was significantly low, indicating the weak effectiveness of the ITF in the Egyptian economy. Full article

The Ostwald ripening process in 3D and 2D systems has been studied in great detail over decades. In the application to surface nanoislands and nanodroplets, it is usually assumed that the capture coefficients of adatoms by supercritical nanoparticles of size $s$ scale as $s^{\alpha }$, where the growth index $\alpha$ is smaller than unity. Here, we study theoretically the Ostwald ripening of 3D and 2D nanoparticles whose capture coefficients scale linearly with $s$. This case includes submonolayer surface islands that compete for the flux of highly diffusive adatoms upon termination of the material influx. We obtain analytical solutions for the size distributions using the Lifshitz–Slezov scaled variables. The distributions over size $s$ and radius $R$ are monotonically decreasing, and satisfy the normalization condition for different values of the Lifshitz–Slezov constant $c$. The obtained size distributions satisfy the Family–Vicsek scaling hypothesis, although the material influx is switched off. The model is validated by fitting the monotonically decreasing size distributions of Au nanoparticles that serve as catalysts for the vapor–liquid–solid growth of III-V nanowires on silicon substrates. Full article

This research analyzes the relationships among environmental factors, organizational structure, strategic orientation, and organizational performance within the Romanian medical system, addressing a theoretical gap in this context. A quantitative approach was applied, analyzing data from 502 employees in the Romanian medical sector. The study used a dual framework, integrating gestalt theory and mediation to examine the environment–structure–strategy–performance relationship. Two-stage cluster analysis, one-way analysis of variance, and partial least squares structural equation modeling tested direct and mediated effects among the variables. From a gestalt perspective, five distinct clusters demonstrated the interplay between environment, structure, and strategy. Romanian healthcare organizations align their structural elements and strategic decisions coherently and distinctly, considering contextual constraints, with implications for several performance dimensions, including patient satisfaction, financial stability, innovation, and internal process improvement. From a mediation perspective, both direct and mediated relationships indicate that organizational structure and strategic orientation positively affect organizational performance and suppress the negative contextual effects. This study contributes theoretically by extending contingency and gestalt theories to the Romanian healthcare context, showing that contextual fit, rather than structural uniformity, determines performance variation. Practically, the findings guide healthcare managers and policymakers in attenuating contextual shocks and improving organizational performance through strategic alignment and flexible structural design. Full article