Search Results (137)

The in situ emulsification synergistic self-profile control system has wide application prospects for efficient development on offshore oil reservoirs. During water flooding in Bohai heavy oil reservoirs, random emulsification occurs with superimposed Jamin effects. Effectively utilizing this phenomenon can enhance the efficient development of offshore oilfields. This study addresses the challenges hindering water flooding development in offshore oilfields by investigating the emulsification mechanism and key influencing factors based on oil–water emulsion characteristics, thereby proposing a novel in situ emulsification flooding method. Based on a fundamental analysis of oil–water properties, key factors affecting emulsion stability were examined. Core flooding experiments clarified the impact of spontaneous oil–water emulsification on water flooding recovery. Two-dimensional T1–T2 NMR spectroscopy was employed to detect pure fluid components, innovating the method for distinguishing oil–water distribution during flooding and revealing the characteristics of in situ emulsification interactions. The results indicate that emulsions formed between crude oil and formation water under varying rheometer rotational speeds (500–2500 r/min), water cuts (30–80%), and emulsification temperatures (40–85 °C) are all water-in-oil (W/O) type. Emulsion viscosity exhibits a positive correlation with shear rate, with droplet sizes primarily ranging between 2 and 7 μm and a viscosity amplification factor up to 25.8. Emulsion stability deteriorates with increasing water cut and temperature. Prolonged shearing initially increases viscosity until stabilization. In low-permeability cores, spontaneous oil–water emulsification occurs, yielding a recovery factor of only 30%. For medium- and high-permeability cores (water cuts of 80% and 50%, respectively), recovery factors increased by 9.7% and 12%. The in situ generation of micron-scale emulsions in porous media achieved a recovery factor of approximately 50%, demonstrating significantly enhanced oil recovery (EOR) potential. During emulsification flooding, the system emulsifies oil at pore walls, intensifying water–wall interactions and stripping wall-adhered oil, leading to increased T2 signal intensity and reduced relaxation time. Oil–wall interactions and collision frequencies are lower than those of water, which appears in high-relaxation regions (T1/T2 > 5). The two-dimensional NMR spectrum clearly distinguishes oil and water distributions. Full article

Gas voids inevitably form during the solidification of phase change materials (PCMs) due to volumetric contraction and thus deteriorate the thermal conductivity of solidified PCMs. In this work, the gas void morphology and distribution in solidified pure paraffin within a cubic thermal energy storage unit are experimentally studied. The three-dimensional structure of the solidified pure paraffin is reconstructed via computed tomography (CT) scanning with a resolution of up to 25 µm. Four distinct morphological types of gas voids are found, including irregular elliptical gas voids, elongated “needle-like” gas voids, micro gas voids, and large circular gas voids. The formation mechanisms of each type are analyzed. The morphology and distribution of gas voids indicate that the solidified pure paraffin structure is anisotropic. The effective thermal conductivity (ETC) of this solid–gas structure is numerically evaluated using lattice Boltzmann simulations, and a two-term power equation is fitted. The results show that the ETC in the vertical direction is significantly lower than in the horizontal direction and the ETC could be reduced by as much as 31.5% due to the presence of gas voids. Full article

Guangxi is among China’s regions most severely affected by karst rocky desertification (KRD). Over the past two decades, global climate change and human activities have jointly led to significant changes in the extent and intensity of KRD in Guangxi. Given this context, it is crucial to comprehensively analyze the spatiotemporal evolution of KRD in Guangxi and its driving forces. This study proposed a novel three-dimensional feature space model for monitoring KRD in Guangxi. We then applied transition matrices, dynamic degree indices, and landscape metrics to analyze the spatiotemporal evolution of KRD. We also proposed a Spatiotemporal Interaction Intensity Index (STII) to quantify mutual influences among KRD patches. Finally, we used GeoDetector to analyze the driving factors of KRD. The results indicate the following: (1) The three-dimensional model showed high applicability for large-scale KRD monitoring, with an overall accuracy of 92.86%. (2) KRD in Guangxi exhibited an overall recovery–deterioration–recovery trend from 2000 to 2023. The main recovery phases were 2005–2015 and 2020–2023. During these phases, both severe and moderate KRD showed strong signals of recovery, including significant declines in area, number of patches, and Landscape Shape Index, along with persistently low STII values. In contrast, from 2015 to 2020, KRD predominantly deteriorated, primarily characterized by transitions from no KRD to potential KRD and from potential KRD to light KRD. (3) For severe KRD patches, the intensity of interaction required from neighboring patches to promote recovery exceeded that which led to deterioration, indicating the difficulty of reversing severe KRD. (4) Slope, land use, and elevation were the main drivers of KRD in Guangxi from 2000 to 2023. Erosive rainfall exhibited a higher explanatory power for KRD than average precipitation. Two-factor interactions significantly enhanced the driving forces of KRD. These findings provide a scientific basis for KRD management. Full article

Hollow electron beams are a promising tool for generating coherent radiation in various frequency ranges. Hollow beams have unique properties, including increased stability and the ability to achieve high current densities without significant deterioration of beam quality. This paper presents the results of a theoretical study on coherent grating transition radiation arising during the interaction between a relativistic hollow electron beam and a flat two-dimensional photonic crystal. The radiation field is calculated using the dipole approximation. Theoretical analysis has shown that, under certain conditions, a high degree of radiation coherence can be achieved. The results open up new possibilities for the creation of new sources of coherent terahertz radiation. Full article

The landslides caused by slope instability are very harmful and have a destructive effect on existing engineering structures such as tunnels, bridges, and houses. At present, the dynamic design of the anchorage structure is mainly based on traditional statics, which fails to fully consider the dynamic evolution process of landslide and its synergistic mechanism with anchorage structure. It is urgent to study the landslide–anchorage structure system considering both the catastrophic process and the evolution process. Based on the advanced combined finite–discrete element method (FDEM), the present study investigates the dynamic response characteristics and evolution process of the landslide–anchorage structure system by adding the dynamic strength reduction method considering the vibration deterioration effect of the structural plane and the combined one-dimensional and entity element model. The results show that the improved FDEM can accurately reproduce the characteristics of the dynamic response and the entire process of the landslide–anchorage structure system and can quantitatively evaluate the dynamic stability of the system. Through the setting of the two working conditions of unreinforced and reinforced slopes, it is verified that the addition of anchor cables can significantly reduce the dynamic response of the slopes. It is also found that the axial force is larger at the structural plane and the failure surface, and the PGA amplification factor positively correlates with the axial force of the anchor cables. The study reveals the dynamic response characteristics and evolution law of the landslide–anchorage structure system under earthquake, which can provide a scientific basis for the reasonable aseismic design of the landslide–anchorage structure system. Full article

This study evaluated the effects of print orientation and thermal aging on the flexural strength (FS) and flexural modulus (FM) of novel permanent three-dimensional (3D)-printed polymethyl methacrylate (PMMA) resins reinforced with nano-zirconia and nano-silica. Bar-shaped specimens (25 × 2 × 2 mm) were fabricated using a digital light processing (DLP) 3D printer (Asiga Max UV, Asiga Inc., Australia) in two orientations (0° and 90°). Specimens underwent three-point bending tests at 24 h and after artificial thermal aging (10,000 and 30,000 cycles) to simulate one and three years of intraoral conditions. Scanning electron microscopy (SEM) was used to analyze fracture patterns. Print orientation did not significantly affect FS or FM (p > 0.05). However, artificial aging significantly reduced FS and FM after 10,000 cycles (p < 0.001), with further deterioration after 30,000 cycles. The micro hybrid resin composite exhibited higher FS than the 3D-printed materials throughout aging. SEM analysis revealed distinct fracture patterns, with 3D-printed resins displaying radial fractures and the micro hybrid composite exhibiting horizontal fractures. These findings indicate that aging plays a more critical role in the long-term mechanical performance of 3D-printed restorative resins than print orientation. This study provides original data on the effects of print orientation and prolonged thermal aging on the mechanical behavior of permanent three-dimensional (3D)-printed dental resins. Furthermore, the comparative evaluation of aging protocols simulating one and three years of intraoral service represents a novel contribution to the existing literature. Further studies are required to optimize the mechanical durability of 3D-printed dental restorations. Full article

Urban lake degradation caused by intensive urbanization necessitates systematic solutions, with water connectivity being a crucial ecological restoration strategy. This study evaluates the two-year effects (2020–2022) of connectivity interventions on seven lakes in Yangshuo, Guilin, classified by connectivity: multi-channel (Mc), single-channel (Sc), and non-connected (Nc). Regular monitoring of the physicochemical parameters and microbial communities revealed significant patterns: multi-channel connected lakes exhibited superior water quality improvement, with trophic state downgrading (weak eutrophic → mesotrophic), but the water quality of Sc-BQ was deteriorating. Seasonal variations showed wet season peaks in pH, DO, COD_Mn, and Chl-a, versus dry season elevations in NH₃-N, NO₃-N, TN, and TP. Correlation analysis identified organic matter as the primary driver of eutrophication, with TN strongly linked to NH₃-N, indicating persistent domestic sewage contamination. Microbial community restructuring was accompanied by changes in water quality, and the abundance and diversity of OTUs decreased after restoration. Notably, Limnohabitans dominated Mc lakes (31.82–35.1%), while Pleurocapsa prevailed (37.85%) in Nc-LH under weak eutrophic conditions. These findings demonstrate that multi-channel connectivity effectively enhances hydrodynamic conditions and pollutant dispersion, whereas inadequate connectivity exacerbates nutrient accumulation. The study provides critical empirical evidence for optimizing urban lake management, emphasizing the necessity of multi-dimensional connectivity designs and targeted control of untreated sewage inputs in water system rehabilitation projects. Full article

Low-flow events significantly impact water users and ecosystems due to reduced flow rates and deteriorating water quality. Elevated water temperatures during these periods have led to economic and ecological consequences. Therefore, water temperature is a key aspect in the context of low-flow risk analysis, and it is essential to model it accurately. This study introduces a one-dimensional water temperature model optimized for integration into low-flow risk analysis frameworks. Results demonstrate good performance in simulating water temperatures for both rivers, with Nash–Sutcliffe efficiency values of 0.85–0.98 and root mean square errors of 0.96–1.96 K. The model was evaluated on two contrasting river systems: the small Selke River and the large Elbe River. The model effectively captures anthropogenic influences and altered environmental conditions. Key factors influencing water temperature varied by river size, with tributaries and shading having more impact on smaller rivers, while air temperature was the primary driver for larger rivers. The model’s computational efficiency enables the practical implementation of long-term risk assessments. This temperature model fulfills the requirements for integration into low-flow risk management frameworks, providing a valuable tool for assessing temperature-related impacts and evaluating mitigation strategies across diverse river systems. Full article

This study investigates the vehicle–bridge coupling vibration performance of corrugated steel web box girder bridges under three-dimensional pavement roughness conditions. To effectively account for these roughness characteristics, a three-dimensional contact constraint method is proposed. The accuracy of the proposed method is first verified, followed by an analysis of a 30 m span corrugated steel web box girder bridge to evaluate the influence of vehicle speed, pavement grade, roughness dimensions, and box girder configurations on the impact factor. The results show that the impact factor does not consistently increase with vehicle speed. As pavement conditions worsen, the impact factor shows an upward trend, with each grade of road surface deterioration resulting in an average 19.1% increase in the impact factor. In most scenarios, three-dimensional pavement roughness results in smaller impact factors compared to two-dimensional pavement roughness, with average reductions of 2.4%, 7.3%, and 13.5% for grade A, B, and C roads, respectively. Replacing the corrugated steel web with a flat steel web leads to an average reduction of 4.2% in the mid-span dynamic deflection of the bridge, despite the impact factors of both configurations being relatively similar. Substituting the concrete bottom slab with an equivalent steel bottom slab increases the mid-span dynamic deflection by an average of 28.4% and nearly doubles the impact factor. The impact factors determined by most national standards generally fall within the range for grade A pavement, suggesting that the calculation methods in these standards are mainly suited for newly constructed bridges or those in good maintenance. Full article

For large-scale multi-objective optimization, it is particularly challenging for evolutionary algorithms to converge to the Pareto Front. Most existing multi-objective evolutionary algorithms (MOEAs) handle convergence and diversity in a mutually dependent manner during the evolution process. In this case, the performance degradation of one solution may lead to the deterioration of the performance of the other solution. This paper proposes a two-stage multi-objective optimization algorithm based on decision variable clustering (LSMOEA-VT) to solve large-scale optimization problems. In LSMOEA-VT, decision variables are divided into two categories and use dimensionality reduction methods to optimize the variables that affect evolutionary convergence. Following this, we performed an interdependence analysis to break down the convergence variables into multiple subcomponents that are more tractable. Furthermore, a non-dominated dynamic weight aggregation method is used to enhance the diversity of the population. To evaluate the performance of our proposed algorithm, we performed extensive comparative experiments against four optimization algorithms across a diverse set of benchmark problems, including eight multi-objective optimization problems and nine large-scale optimization problems. The experimental results show that our proposed algorithm performs well on some test functions and has certain competitiveness. Full article

The combination of global climate change and the urban heat island effect has given rise to a deterioration in the livability of residential districts within cities, posing challenges to enhancing the health quality of urban environments. Meanwhile, the intensification of daytime changes in temperature and humidity in residential districts has rendered the sensory representation of the urban heat island effect more pronounced. This study selects the residential districts in Fuzhou City as the research case area, which have witnessed a discernible warming trend in recent years, and acquires temperature and humidity parameter data at three time periods (early morning, noon, and evening) to represent the daytime temperature and humidity change phase. Through aerial photography and field research, three types of spatial morphological indicators (buildings I, vegetation II, and the combination of buildings and vegetation II) of residential districts are quantified to represent the three-dimensional spatial form of the case study area. The analysis results show the following: ➀ Residential districts experience two phases of daytime changes in temperature and humidity: a warming and drying phase (WDP) in the morning and a cooling and humidifying phase (CHP) in the afternoon. The characteristics of changes in temperature and humidity show a spatial correlation with each other. ➁ The impact of urban three-dimensional morphology on changes in temperature and humidity in WDP is minor, whereas, in CHP, it is influenced by Class II and Class III indicators. The two types of urban morphology exert a synergistic regulatory effect on changes in temperature and humidity. ➂ Vegetation has a significant regulatory effect on temperature and humidity variations in residential areas through changes in its three-dimensional form. Enlarging the area of individual trees while reducing their canopy volume can restrain the warming and dehumidification of residential districts and promote cooling and humidification. In contrast to only planting trees, a vegetation configuration combining trees, shrubs, and grass can bring a more obvious cooling effect to residential districts. The research results can provide a reference for urban planners in the planning and design of residential areas as well as the optimization and improvement of urban living environments. Full article

Chemical modification is an environmentally friendly option for wood preservation. It can improve the performance and dimensional stability of wood, increase its resistance to deterioration and ensure safe disposal once out of service. Wood acetylation is the esterification of accessible hydroxyl groups in the cell wall with acetic anhydride, which reduces the hygroscopicity of wood. Acetic acid is obtained as a byproduct of the reaction. The aim of this work is to determine the best reaction conditions for the acetylation of Pinus taeda wood with acetic anhydride. The experimental design used was a 2² factorial design with three repetitions in the midpoints. Reaction temperature and reaction time were taken as independent variables, each at two levels. The weight gain percentage of wood (WPG) and its chemical changes were used as response variables. The durability of the wood acetylated under the best treatment conditions as determined before was tested against decay fungi (Gloeophyllum separium and Trametes versicolor). The results show that temperature was the most impactful variable on the WPG results. Higher WPGs were obtained at temperatures above 100 °C. The acetylated wood was highly resistant to fungal attack, with very low mass losses. Full article

Automotive millimeter-wave (MMW) synthetic aperture radar (SAR) systems can achieve high-resolution images of detection areas, providing environmental perceptions that facilitate intelligent driving. However, curved path is inevitable in complex urban road environments. Non-uniform spatial sampling, brought about by curved path, leads to cross-coupling and spatial variation deteriorates greatly, significantly impacting the imaging results. To deal with these issues, we developed an Extended Omega-K Algorithm (EOKA) for an automotive SAR with a curved path. First, an equivalent range model was constructed based on the relationship between the range history and Doppler frequency. Then, using azimuth time mapping, the echo data was reconstructed with a form similar to that of a uniform linear case. As a result, an analytical two-dimensional (2D) spectrum was easily derived without using of the method of series reversion (MSR) that could be exploited for EOKA. The results from the parking lot, open road, and obstacle experimental scenes demonstrate the performance and feasibility of an MMW SAR for environmental perception. Full article

Lithium ion (Li-ion) battery packs have become the most popular option for powering electric vehicles (EVs). However, they have certain drawbacks, such as high temperatures and potential safety concerns as a result of chemical reactions that occur during their charging and discharging processes. These can cause thermal runaway and sudden deterioration, and therefore, efficient thermal management systems are essential to boost battery life span and overall performance. An electrochemical-thermal (ECT) model for Li-ion batteries and a conjugate heat transfer model for three-dimensional (3D) fluid flow and heat transfer are developed using COMSOL Multiphysics^®. These are used within a novel computational fluid dynamics (CFD)-enabled multi-objective optimization approach, which is used to explore the effect of the mini-channel cold plates’ geometrical parameters on key performance metrics (battery maximum temperature ($T_{max}$), pressure drop ($∆P$), and temperature standard deviation ($T_{\sigma }$)). The performance of two machine learning (ML) surrogate methods, radial basis functions (RBFs) and Gaussian process (GP), is compared. The results indicate that the GP ML approach is the most effective. Global minima for the maximum temperature, temperature standard deviation, and pressure drop ($T_{max}$, $T_{\sigma }$, and $∆P$, respectively) are identified using single objective optimization. The third version of the generalized differential evaluation (GDE3) algorithm is then used along with the GP surrogate models to perform multi-objective design optimization (MODO). Pareto fronts are generated to demonstrate the potential trade-offs between $T_{max}$, $T_{\sigma }$, and $∆P$. The obtained optimization results show that the maximum temperature dropped from 36.38 to 35.98 °C, the pressure drop dramatically decreased from 782.82 to 487.16 Pa, and the temperature standard deviation decreased from 2.14 to 2.12 K; the corresponding optimum design parameters are the channel width of 8 mm and the horizontal spacing near the cold plate margin of 5 mm. Full article

Stereo matching technology, enabling the acquisition of three-dimensional data, holds profound implications for marine engineering. In underwater images, irregular object surfaces and the absence of texture information make it difficult for stereo matching algorithms that rely on discrete disparity values to accurately capture the 3D details of underwater targets. This paper proposes a stereo method based on an energy function of Markov random field (MRF) with 3D labels to fit the inclined plane of underwater objects. Through the integration of a cross-based patch alignment approach with two label optimization stages, the proposed method demonstrates features akin to segment-based stereo matching methods, enabling it to handle images with sparse textures effectively. Through experiments conducted on both simulated UW-Middlebury datasets and real deteriorated underwater images, our method demonstrates superiority compared to classical or state-of-the-art methods by analyzing the acquired disparity maps and observing the three-dimensional reconstruction of the underwater target. Full article