Search Results (144)

The oil and gas industry is increasingly challenged by the global transition toward renewable energy systems aimed at reducing carbon emissions. Nevertheless, opportunities remain to mitigate the environmental impacts associated with ongoing oil and gas operations. One of the major environmental challenges in this sector is the extensive use and treatment of water. Membrane-based separation has emerged as an effective technology for oil–water separation due to its ability to overcome limitations associated with conventional treatment methods. This study aims to build a CFD model to investigates the influence of operational hydrodynamic conditions on membrane separation, including transmembrane pressure 202, 101, 50, 10 kPa, crossflow velocity 0.08 m/s, 0.116 m/s, 0.33 m/s, 0.66 m/s, and oil droplet diameter 1, 5, 10, 50, 100 µm, on membrane performance in addition to different oil concentrations 1%, 2%, 4%, 8% using Eulerian-Eulerian multiphase model. This is done by experimentally extracting the membrane water resistance, which is found to be 6.46 × 10¹⁰ (1/m) and using it as an input to the numerical model. The results indicate that permeate flux is primarily governed by transmembrane pressure, in agreement with Darcy’s law, while fouling development along the membrane length is mainly influenced by crossflow velocity and oil droplet size. Where it was found that for large droplets 100 µm and 50 µm the buoyancy forces were large enough to lift the oil droplets away from the membrane at velocities 0.08, 0.16 and 0.33 m/s while smaller droplets remained at the membrane surface In addition, backward diffusion, which has been emphasized in previous studies, was found to play a comparatively minor role in the present numerical analysis. Full article

To accurately predict the rate of penetration (ROP) for steeply inclined coal seam blocks, this paper proposes a data-driven ROP prediction method incorporating feature processing. First, Savitzky–Golay (SG) filtering is applied to key continuous monitoring parameters to mitigate the impact of noise on model training. Subsequently, features are comprehensively screened across linear, monotonic, and nonlinear dependency dimensions using the Pearson correlation coefficient, Spearman correlation coefficient, and mutual information evaluation, identifying structural parameters significantly contributing to ROP. Based on this, a Time Convolution Network (TCN)-Bidirectional Long Short-Term Memory (BiLSTM)-Attention prediction model is constructed: TCN extracts local temporal patterns, BiLSTM captures forward and backward dependencies, and the attention mechanism adapts weight distribution for information across different time steps. This architecture significantly enhances the model’s ability to capture complex operational variations and improves prediction accuracy. Experimental results demonstrate that compared to benchmark models such as BiLSTM, TCN-BiLSTM, and BiLSTM-Attention, our method achieves superior performance across all evaluation metrics and exhibits strong generalization capabilities on diverse operational datasets. Full article

This study addresses the problem of optimal resource allocation in nonlinear multi-module dynamic systems arising in complex computational and techno-economic processes, where numerical stability and strict enforcement of structural constraints are critical. The objective is to develop a computationally efficient optimal control algorithm capable of handling bilateral control constraints and external balance conditions without resorting to large-scale nonlinear programming or boundary-value shooting. The proposed method is based on a modified Lagrangian formulation, in which bilateral Karush–Kuhn–Tucker (KKT) conditions are analytically embedded into the optimality system. The resulting computational scheme consists of a coupled system of matrix and vector differential equations solved through a non-iterative backward–forward integration procedure. Numerical experiments conducted on a nonlinear model with Cobb–Douglas-type operators demonstrate the stable convergence of the trajectories toward a stationary regime, strict satisfaction of bilateral constraints, and consistent enforcement of balance relations throughout the planning horizon. Empirical scalability analysis indicates approximately cubic computational complexity with respect to the state dimension, while sensitivity tests confirm the numerical robustness across different integration tolerances and ODE solvers. These results demonstrate that the proposed structure-preserving framework provides a computationally stable and practically implementable approach to constrained optimal control in nonlinear multi-module systems. Full article

Accurate carbon price forecasting is essential for transforming complex carbon trading markets into efficiently managed and stably operating systems. Existing long-term time series forecasting methods struggle to capture the nonlinear and non-stationary characteristics inherent in carbon prices. To address this limitation, we propose the Temporal Trend and Fluctuation Learning (TTFL) model for interval-valued carbon price forecasting. The model first uses wavelet decomposition to separate the forecasting task into two branches: Price Trend Learning (PTL) and Price Fluctuation Learning (PFL). The PTL branch adopts a forward–backward enhanced Mamba architecture to extract low-frequency, long-term trend features. This design facilitates price interactions across time steps. The enhanced Mamba module leverages a state space model (SSM) to preserve historical information selectively and employs a forgetting gate to recover missing information. As a result, the model captures complementary dependencies across different price points, improving prediction reliability. The PFL branch integrates an attention mechanism with the standard Mamba architecture to model high-frequency temporal dynamics. It provides fine-grained short-term volatility information essential for market participants. We also introduce an interval-valued recovery loss function. This loss quantifies the overlap between predicted and actual interval prices, emphasizes trend learning, and stabilizes model training. We evaluate the TTFL model on three real-world carbon trading markets. Comparative experiments demonstrate that TTFL achieves superior prediction accuracy and robustness relative to baseline methods. Through collaborative learning and selective state space modeling, our approach not only outperforms traditional forecasting models but also offers stakeholders a practical tool for navigating complex carbon market environments. This work contributes a novel forecasting paradigm that integrates multivariate collaborative learning with selective state space modeling. It provides actionable insights for policymaking, investment strategy development, and risk management in the energy and environmental sectors. Full article

In this study, a three-dimensional (3D) model is developed based on an actual small forestry crawler tractor, to analyze its overturning and rollover behaviors, and a corresponding simulation model is constructed. The accuracy of the 3D model is validated by comparing its dimensions and center of gravity with those of the physical tractor, and the fidelity of the simulation model is verified using static sidelong falling angle, minimum turning radius, and driving tests. The developed simulation framework was employed to investigate the dynamic behavior of the small forestry crawler tractor, focusing on roll and pitch angular velocities across different obstacle heights, slope angles, and driving speeds. Backward rollover was not observed within the tractor’s realistic operating speed range, indicating that backward rollover is not the dominant risk mode. In contrast, lateral overturning occurs under all driving scenarios, and increases in driving speed and obstacle height lead to higher roll angular velocities, increasing the risk of lateral overturning. Across all conditions, the likelihood of lateral overturning surges when the roll angular velocity enters the 80–100°/s range, with obstacle height exerting the greatest influence. In conclusion, the small forestry crawler tractor is more prone to lateral overturning than backward rollover when driving on inclined surfaces. A distinct threshold roll angular velocity is identified as the onset point of lateral overturning, which will vary according to the tractor’s specifications. This study is a quantitative study of a small forestry crawler tractor and does not correlate with a full-scale tractor. While angular velocity values vary during lateral overturning and backward rollover, this study was conducted to identify trends under various driving conditions. Further work is required to apply the proposed analysis methodology to full-scale agricultural and forestry machinery and validate it with real-world operational data. Full article

This paper presents a dual four-port circularly polarized (CP) MIMO antenna based on substrate integrated waveguide (SIW) technology for sub-6 GHz applications. The design consists of two identical four-port SIW-based CP-MIMO antennas arranged in a mirror-symmetric configuration with an air gap of 15 mm. Each antenna employs four symmetrically arranged cross-shaped SIW patches excited by coaxial probes. Bidirectional radiation is achieved by applying a 180° phase difference between corresponding ports of the mirror symmetric configuration, referred to as the Backward-Radiating Unit (BRU) and the Forward-Radiating Unit (FRU). The bidirectional radiation mechanism is supported by array-factor-based theoretical modelling, which explains the constructive and destructive interference under phase-controlled excitation. To ensure high isolation and stable polarization performance, the antenna design incorporates defected ground structures, inter-element decoupling strips, and vertical metallic vias. Simulations indicate an operating band from 5.1 to 5.4 GHz. Measurements show a −10 dB bandwidth from 5.25 to 5.55 GHz, with the frequency shift attributed to fabrication tolerances and measurement uncertainties. The antenna achieves inter-port isolation better than −15 dB. A 3 dB axial-ratio bandwidth is maintained across the operating band. Measured axial-ratio values remain below 3 dB from 5.25 to 5.55 GHz, while simulations predict a corresponding range from 5.1 to 5.4 GHz. The proposed configuration achieves a peak gain exceeding 4 dBi and maintains an envelope correlation coefficient below 0.05. These results confirm its suitability for CP-MIMO systems with controlled spatial coverage. With a physical size of 0.733λ₀ × 0.733λ₀ per array, the proposed antenna is well-suited for vehicular and space-constrained wireless systems requiring bidirectional CP-MIMO coverage. Full article

Recent advances in mobile robotics have emphasized the need for systems capable of operating in unstructured environments, combining obstacle negotiation, stability, and adaptability. This study presents the preliminary design and testing of Brush.Q, an articulated ground robot featuring a novel structure distinct from existing wheel-legged robots, equipped with compliant brush-like wheels composed of multiple spokes. The main contribution is the experimental analysis of suspension capability across different wheel geometric profiles, combined with the assessment of obstacle-climbing performance. A simplified prototype was constructed to evaluate the effects of wheel rotation direction, spoke number, and spoke tapering. Results show that reducing the number of spokes improves obstacle-climbing at the expense of suspension, while higher spoke count and compliant geometry enhance suspension and stability. Spoke tapering improves obstacle climbing in the backward-facing configuration but consistently reduces suspension. Overall, these findings highlight the critical role of wheel geometry and the potential for reconfigurable spoked wheels to enhance adaptability and versatility in unstructured terrains. Full article

This review provides a comprehensive analysis of the technological, environmental, economic, regulatory, and social dimensions shaping the development and operation of agricultural biogas plants. The paper adopts a primarily European perspective, reflecting the comparatively high share of agricultural inputs in anaerobic digestion (AD) across EU Member States, while drawing selective comparisons with global contexts to indicate where socio-geographical conditions may lead to different outcomes. It outlines core principles of the AD process and recent innovations—such as enzyme supplementation, microbial carriers, and multistage digestion systems—that enhance process efficiency and cost-effectiveness. The study emphasises substrate optimisation involving both crop- and livestock-derived materials, together with the critical management of water resources and digestate within a circular-economy framework to promote sustainability and minimise environmental risks. Economic viability, regulatory frameworks, and social dynamics are examined as key factors underpinning successful biogas implementation. The paper synthesises evidence on cost–benefit performance, investment drivers, regulatory challenges, and support mechanisms, alongside the importance of community engagement and participatory governance to mitigate land-use conflicts and ensure equitable rural development. Finally, it addresses persistent technical, institutional, environmental, and social barriers that constrain biogas deployment, underscoring the need for integrated solutions that combine technological advances with policy support and stakeholder cooperation. This analysis offers practical insights for advancing sustainable biogas use in agriculture, balancing energy production with environmental stewardship, food security, and rural equity. The review is based on literature identified in Scopus and Web of Science for 2007 to 2025 using predefined keyword sets and supplemented by EU policy and guidance documents and backward- and forward-citation searches. Full article

Background: Patients with multiple sclerosis (PwMS) frequently experience dysphagia, which affects their quality of life. The swallowing disturbance questionnaire (SDQ) has demonstrated potential in screening dysphagia in different disorders. The objective of this study was to evaluate the validity and reliability of the Persian version of SDQ in PwMS. Methods: In this cross-sectional study, 198 PwMS were enrolled. The translation of SDQ into Persian was performed using the forward–backward method. Participants completed both the SDQ and the Dysphagia in Multiple Sclerosis (DYMUS) questionnaires. Convergent validity was assessed using the Spearman correlation, construct validity was evaluated by principal component analysis (PCA), and reliability was assessed by Cronbach’s alpha. Screening ability was evaluated with receiver operating characteristic (ROC) curve analysis, using DYMUS as the reference measure. Results: The Persian SDQ showed high internal consistency (Cronbach’s alpha = 0.913) after removing one item. PCA revealed a single dominant factor accounting for 49.4% of the variance. The 14-item SDQ correlated strongly with both DYMUS (Spearman’s rho = 0.62, p < 0.001) and Expanded Disability Status Scale (EDSS) (Spearman’s rho = 0.388, p < 0.001). The area under the curve of 0.957 revealed high screening power with a sensitivity of 91.7% and a specificity of 88.9%. Conclusions: The Persian SDQ is a valid and reliable tool for early detection and quick monitoring of dysphagia in PwMS. Full article

Given the projection of the impact of climate change and the uncertainty caused by geopolitical volatility, minimising emissions has become an urgent priority for the shipping industry. In this context, the aim of the present study is the calculation and estimation of emissions generated by ship operations within a maritime transportation network, as well as the identification of the optimal route that minimises both emissions and travel time. Emission estimation is carried out using methodologies and assumptions from the Fourth IMO GHG Study. The decision-making, along with the optimisation process, is performed through backward dynamic programming, following a multi-objective optimisation framework. Specifically, the analysis is carried out on both a theoretical and a realistic network. In both cases, various scenarios are examined, including different approaches to vessel speed, some of which incorporate probabilistic speed distributions, as well as scenarios involving uncertainty regarding port availability. Additionally, the resilience of the network is examined, focusing on the additional burden in terms of emissions and travel time when a port is unexpectedly unavailable and a route adjustment is required. The calculations and optimisation are carried out using Excel and the @Risk software by Palisade, with the latter enabling the incorporation of probability distributions and the execution of Monte Carlo simulations. Full article

Background/Objectives. Patient-Reported Outcome Measures (PROMs) capture patients’ perspectives about their health status, quality of life, and medical care outcomes. LIMB-Q Kids is a validated PROM designed to assess health-related quality of life (HRQL) in children with lower limb differences. It evaluates physical, social, and psychological function; symptoms related to the leg, hip, knee, foot and ankle; leg-related distress, appearance, and school-related concerns. It has now been translated and culturally adapted from English to other languages. The aim of this study was to translate and culturally adapt LIMB-Q Kids to Hebrew. Methods. Following international guidelines, two independent forward translations from English to Hebrew were produced and reconciled into a single version. A backward translation was then compared with the original to identify discrepancies. This draft underwent cognitive debriefing interviews (CDIs) with 11 children (ages 8–15) having lower limb differences to assess comprehension and cultural relevance. Results. CDIs revealed general issues including lengthy or unclear text, high-level language, cultural unfamiliarity and duplication of descriptors. Specific to Hebrew, issues included gender inflections and the need for vowel diacritics to support younger, less proficient readers. Revisions to 14 items were made. Conclusions. A translation and cultural adaption (TCA) process led to a linguistically validated and culturally adapted Hebrew version of LIMB-Q Kids. It can now be used for the clinical follow-up of children with lower limb differences including pre- and post-operatively, and as an aid to decision-making for surgery. Full article

Using the Laplace transform and the Gamma function, we obtain the Laplace-type transform, with the property of mapping a function to a functional sequence, which cannot be realized by the Laplace transform. In addition, we construct a backward difference as a generalization of the backward difference operator ∇. By connecting it to the Laplace-type transform, we deduce a method for solving difference equations and, relying on classical orthogonal polynomials, for obtaining combinatorial identities. A table of some elementary functions and their images is at the end of the text. Full article

This paper presents the design of a circularly polarized RFID ground mat antenna for UHF-band sports-event applications. Considering a practical sports-event timing system, the ground-based mat antenna with characteristics of a low-backward radiation and circular polarization is proposed. A multilayer square patch antenna using an acrylic dielectric substrate with a wideband branch-line coupler feeding network is employed to improve overall radiation efficiency, which, in turn, provides two excitation port with a phase difference of 90°. Thus, right-hand circular polarization can be obtained. Instead of a conventional FR4–air–FR4 structure, the proposed FR4–acrylic–FR4 composite configuration is adopted to substantially increase the antenna’s mechanical strength and durability against external pressure from runners. The antenna’s performance is attributed to the use of an effective composite dielectric constant and an optimized design of its parameters. Additionally, the patch antenna’s low-backward radiation characteristic helps reduce multipath interference in real-world applications. The measured results are in good agreement with the simulated data, validating the proposed antenna design. In order to further assess the practical performance of the antenna, outdoor measurements are carried out to validate the estimated reading distances derived from controlled anechoic chamber tests. The measured return loss remained below −10 dB across the frequency range of 755–990 MHz, exhibiting a slight discrepancy compared to the simulated bandwidth of 800–1030 MHz. For the characteristic of the circular polarization, the measured axial ratio is below 3 dB within the range of 860–920 MHz. While a more relaxed criterion of an axial ratio below 6 dB is considered, the operating frequency range extends from 560 MHz to 985 MHz, which falls within the frequency band relevant for RFID reader applications. Full article

Efficient simulation of multiphase, multicomponent fluid flow in heterogeneous reservoirs is critical for optimizing hydrocarbon recovery. In this study, we investigate advanced linearization techniques for fully implicit compositional reservoir simulations, a problem characterized by highly nonlinear governing equations that challenge both accuracy and computational efficiency. We implement four methods—finite backward difference (FDB), finite central difference (FDC), operator-based linearization (OBL), and residual accelerated Jacobian (RAJ)—within an MPI-based parallel framework and benchmark their performance against a legacy simulator across three test cases: (i) a five-component hydrocarbon gas field with CO₂ injection, (ii) a ten-component gas field with CO₂ injection, and (iii) a ten-component gas field case without injection. Key quantitative findings include: in the five-component case, OBL achieved convergence with only 770 nonlinear iterations (compared to 841–843 for other methods) and reduced operator computation time to 9.6 of total simulation time, highlighting its speed for simpler systems; in contrast, for the more complex ten-component injection, FDB proved most robust with 706 nonlinear iterations versus 723 for RAJ, while OBL failed to converge; in noninjection scenarios, RAJ effectively captured nonlinear dynamics with comparable iteration counts but lower overall computational expense. These results demonstrate that the optimal linearization strategy is context-dependent—OBL is advantageous for simpler problems requiring rapid solutions, whereas FDB and RAJ are preferable for complex systems demanding higher accuracy. The novelty of this work lies in integrating these advanced linearization schemes into a scalable, parallel simulation framework and providing a comprehensive, quantitative comparison that extends beyond previous efforts in reservoir simulation literature. Full article

A rotating imperfect ring resonator of the gyroscope is modeled by a rotating thin ring with evenly distributed point masses. The free response of the rotating ring structure at constant speed is investigated, including the steady elastic deformation and wave response. The dynamic equations are formulated by using Hamilton’s principle in the ground-fixed coordinates. The coordinate transformation is applied to facilitate the solution of the steady deformation, and the displacements and tangential tension for the deformation are calculated by the perturbation method. Employing Galerkin’s method, the governing equation of the free vibration is casted in matrix differential operator form after the separation of the real and imaginary parts with the inextensional assumption. The natural frequencies are calculated through the eigenvalue analysis, and the numerical results are obtained. The effects of the point masses on the natural frequencies of the forward and backward traveling wave curves of different orders are discussed, especially on the measurement accuracy of gyroscopes for different cases. In the ground-fixed coordinates, the frequency splitting results in a crosspoint of the natural frequencies of the forward and backward traveling waves. The finite element method is applied to demonstrate the validity and accuracy of the model. Full article