Search Results (579)

Background/Objectives: Molar distalization with clear aligners is increasingly used for Class II malocclusions, yet the associated periodontal ligament (PDL) stress and potential root resorption risk remain unclear. Three-dimensional finite element analysis (3D FEA) provides insight into these factors, but variations in attachments and anchorage strategies merit systematic evaluation. To determine whether molar distalization with clear aligners exceeds the PDL stress thresholds for root resorption and to assess how different attachments and anchorage methods influence stress distribution. Methods: In accordance with the PRISMA 2020 guidelines, four electronic databases were searched without language or date restrictions. Studies were included if they (1) employed 3D FEA, (2) analyzed PDL stress during aligner-based molar distalization, and (3) assessed root resorption risk or stress thresholds. Two reviewers independently screened and extracted data, yielding eight studies. Results: Attachments lowered PDL stress and distributed forces more evenly, reducing root resorption risk compared with no attachment cases. Micro-implants shifted stress to molars and protected anterior teeth; palatal mini-screws achieved greater distalization but higher stress, requiring caution, while buccal mini-screws showed lower stress in first premolar roots. Placing a mini-screw between first and second molars yielded the lowest, most uniform stress. Class II elastics—with precision cuts—demonstrated low compressive stress and improved anchorage, although some resorption risk persisted in maxillary anteriors. Conclusions: Clear aligner–based molar distalization can elevate PDL stress to potentially resorptive levels. Although attachments, micro-implants, and Class II elastics improve stress distribution and lessen root resorption risk, it is not fully eliminated. Careful, individualized treatment planning remains essential, and further clinical validation is needed to establish definitive guidelines. Full article

This paper investigates the critical filling height of embankments over soft soil using three-dimensional (3D) upper-bound limit analysis based on a rotational log-spiral failure mechanism. Soft soils are characterized by low shear strength and high compressibility, making the accurate determination of critical filling height essential for evaluating embankment stability. Unlike conventional two-dimensional (2D) analyses, the proposed 3D method captures the true failure mechanism of embankments, providing more realistic and reliable results. The upper-bound analysis equations are derived using the principle of virtual work and solved efficiently through the genetic algorithm (GA), which avoids the limitations of traditional loop and random searching algorithms. The proposed solution is validated by comparing it with existing studies on slope stability and demonstrates higher accuracy and computational efficiency. Parametric studies are conducted to evaluate the influence of the depth–height ratio (the ratio of soft soil depth to embankment height) on the failure width of the embankment, the critical failure surface, and the critical filling height. Results show that the critical failure surface is tangential to the bottom of the soft soil layer and the critical filling height increases as the depth–height ratio decreases. The findings provide a set of critical filling heights calculated under various soft soil depths, strength parameters, and embankment geometries, offering practical guidance for embankment design. Full article

Convolutional neural networks (CNNs) have been widely and successfully demonstrated for closed set recognition in gait identification, but they still lack robustness in open set recognition for unknown classes. To improve the disadvantage, we proposed a convolutional neural network autoencoder (CNN-AE) architecture for user classification based on plantar pressure gait recognition. The model extracted gait features using pressure-sensitive mats, focusing on foot pressure distribution and foot size during walking. Preprocessing techniques, including region of interest (ROI) selection, feature image extraction, and data horizontal flipping, were utilized to establish a CNN model that assessed gait recognition accuracy under two conditions: without carried items and carrying a 500 g object. To extend the application of the CNN to open set recognition for unauthorized personnel, the proposed convolutional neural network-autoencoder (CNN-AE) architecture compressed the average foot pressure map into a 64-dimensional feature vector and facilitated identity determination based on the distances between these vectors. Among 60 participants, 48 were classified as authorized individuals and 12 as unauthorized. Under the condition of not carrying an object, an accuracy of 91.218%, precision of 93.676%, recall of 90.369%, and an F1-Score of 91.993% were achieved, indicating that the model successfully identified most actual positives. However, when carrying a 500 g object, the accuracy was 85.648%, precision was 94.459%, recall was 84.423%, and the F1-Score was 89.603%. Full article

Miscible gas flooding improves oil displacement through mass exchange between oil and gas phases. It is one of the most efficient enhanced oil recovery methods for intermediate density oil reservoirs. In this work, analytical solutions for saturation, concentration and pressure are derived for oil displacement by a partially miscible gas injection at a constant rate. The mathematical model considers two-phase, three-component fluid flow in a one-dimensional homogeneous reservoir initially saturated by a single oil phase. Phase saturations and component concentrations are described by a 2×2 hyperbolic system of partial differential equations, which is solved by the method of characteristics. Once this Goursat–Riemann problem is solved, the pressure drop between two points in the porous media is obtained by the integration of Darcy’s law. The solution of this problem may present three different fluid regions depending on the rock–fluid parameters: a single-phase gas region near the injection point, followed by a two-phase region where mass transfer takes place and a single-phase oil region. We considered the single-phase gas and the two-phase gas/oil regions as incompressible, while the single-phase oil region may be incompressible or slightly compressible. The solutions derived in this work are applied for a specific set of rock and fluid properties. For this data set, the two-phase region displays rarefaction waves, shock waves and constant states. The pressure behavior depends on the physical model (incompressible, compressible and finite or infinite porous media). In all cases, the injection pressure is the result of the sum of two terms: one represents the effect of the mobility contrast between phases and the other represents the single-phase oil solution. The solutions obtained in this work are compared to an equivalent immiscible solution, which shows that the miscible displacement is more efficient. Full article

A novel concept of cold neutron source employing chessboard or staircase assemblies of high-aspect-ratio rectangular para-hydrogen moderators with well-developed and practically fully illuminated surfaces of the individual moderators is proposed. An analytic approach for calculating the brightness of para-hydrogen moderators is introduced. Because the brightness gain originates from a near-surface effect resulting from the prevailing single-collision process during thermal-to-cold neutron conversion, high-aspect-ratio rectangular cold moderators offer a significant increase, up to a factor of 10, in cold neutron brightness compared to a voluminous moderator. The obtained results are in excellent agreement with MCNP calculations. The chessboard or staircase assemblies of such moderators facilitate the generation of wide neutron beams with simultaneously higher brightness and intensity compared to a para-hydrogen-based cold neutron source made of a single moderator (either flat or voluminous) of the same cross-section. Analytic model calculations indicate that gains of up to approximately 2.5 in both brightness and intensity can be achieved compared to a source made of a single moderator of the same width. However, these gains are affected by details of the moderator–reflector assembly and should be estimated through dedicated Monte Carlo simulations, which can only be conducted for a particular neutron source and are beyond the scope of this general study. The gain reduction in our study, from a higher value to 2.5, is mostly caused by these two factors: the limited volume of the high-density thermal neutron region surrounding the reactor core or spallation target, which restricts the total length of the moderator assembly, and the finite width of moderator walls. The relatively large length of moderator assemblies results in a significant increase in pulse duration at short pulse neutron sources, making their straightforward use very problematic, though some applications are not excluded. The concept of “low-dimensionality” in moderators is explored, demonstrating that achieving a substantial increase in brightness necessitates moderators to be low-dimensional both geometrically, implying a high aspect ratio, and physically, requiring the moderator’s smallest dimension to be smaller than the characteristic scale of moderator medium (about the mean free path for thermal neutrons). This explains why additional compression of the moderator along the longest direction, effectively giving it a tube-like shape, does not result in a significant brightness increase comparable to the flattening of the moderator. Full article

This study analyzed the influence of the mechanical properties of two-step backfill on the stability of mining sites. The study focused on the one-step adhesive backfill of segmented backfill mining in a mine in Shandong Province, where the front wall was exposed and the back wall was compressed. A three-dimensional mechanical model of the front wall exposed, back wall compressed cemented filling material considering the mechanical properties of the two-step weakly cemented filling material was established through theoretical analysis. On this basis, considering the influence of different mechanical properties (elastic modulus, internal friction angle, cohesion, and Poisson’s ratio) of two-step weakly cemented filling on one-step cemented filling, FLAC 3D 6.00.60 numerical simulation software was used to study the influence of various factors on the horizontal displacement distribution of cemented filling under single-sided exposure conditions using numerical simulation methods. The results show that the adhesive filling material exposed on one side is subjected to lateral pressure from adjacent weak adhesive filling materials, and its stability is affected by the contact area and mechanical properties of the weak adhesive filling material. Increasing the elastic modulus of the two-step weak adhesive filling material from 100 MPa to 500 MPa can reduce the maximum horizontal displacement of the one-step adhesive filling material from 116 mm to 32 mm, a decrease of about 72%. Similarly, increasing the cohesive force from 0.09 MPa to 0.21 MPa can reduce displacement from 96 mm to 33 mm, a decrease of 66%. Improving the mechanical properties of the two-step weakly cemented filling material can reduce the tendency of tailings to slide and collapse, and can reduce the lateral pressure applied by the cemented filling material. The horizontal displacement law of the two-step cemented filling material with front wall exposure and rear wall compression is basically similar under different mechanical properties of the one-step weakly cemented filling material. In the vertical direction, as the height of the filling material increases, the horizontal displacement first slowly increases to the maximum value and then slowly decreases. As the mechanical properties of the two-step weakly cemented filling increase, the horizontal displacement of the one-step cemented filling decreases. Full article

This study investigates the aroma characterization of unique white tea varieties from the Lüchun county of Yunnan province, Mainland China. These include shaken, unshaken, steam-cooked, and compressed varieties. The aroma profile of white tea varieties was analyzed using two-dimensional gas chromatography–olfactometry–mass spectrometry (GC×GC-O-MS), electronic nose (e-nose), and descriptive sensory evaluation. A chemometric approach was used to compare sensory scores to instrumental data. A total of 154 volatile compounds were detected in 16 white tea varieties through GC×GC-O-MS. Among these, 133 compounds were successfully identified through the National Institute of Standards and Technology (NIST) library, and 21 were listed as unknown. The identified volatile classes include aldehydes, such as hexanal and heptanal, which contribute to the green aroma of white tea, and alcohols like 2-heptanol and 3-hexen-1-ol, which exhibit fresh and floral odor notes. The content and relative odor active values (r-OAVs) of the volatile compounds were calculated. The chemometric data revealed significant variations in volatile contents between shaken and unshaken white tea varieties. The orthogonal partial least squares discriminant analysis (OPLS-DA) model showed strong validity and stability. This study describes the impact of processing conditions on the flavor profile of white tea and provides a solid foundation for monitoring the aroma quality of different processed white tea varieties. Full article

Five-dimensional (5-D) light field videos (LFVs) capture spatial, angular, and temporal variations in light rays emanating from scenes. This leads to a significantly large amount of data compared to conventional three-dimensional videos, which capture only spatial and temporal variations in light rays. In this paper, we propose an LFV compression technique using low-complexity 5-D approximate discrete cosine transform (ADCT). To further reduce the computational complexity, our algorithm exploits the partial separability of LFV representations. It applies two-dimensional (2-D) ADCT for sub-aperture images of LFV frames with intra-view and inter-view configurations. Furthermore, we apply one-dimensional ADCT to the temporal dimension. We evaluate the performance of the proposed LFV compression technique using several 5-D ADCT algorithms, and the exact 5-D discrete cosine transform (DCT). The experimental results obtained with LFVs confirm that the proposed LFV compression technique provides a more than 250 times reduction in the data size with near-lossless fidelity with a peak-signal-to-noise ratio greater than 40 dB and structural similarity index greater than 0.9. Furthermore, compared to the exact DCT, our algorithms requires approximately 10 times less computational complexity. Full article

The effects of high-temperature modified phosphogypsum (HPG), incorporated at contents of 40%, 50%, and 60%, on the compressive strength and elastic modulus of mortar and concrete were investigated. Additionally, the influence of graded granulated blast furnace slag powder (GGBS), quicklime, and silica fume on the mechanical properties of HPG-based mortar (HPGM) and HPG-based concrete (HPGC) was discussed. Moreover, the microstructure of HPGM was analyzed using scanning electron microscopy (SEM). A two-dimensional mesoscale model of HPGC was developed to predict how variations in HPG content, coarse aggregate characteristics, and interfacial transition zone (ITZ) characteristics influence the compressive strength and elastic modulus of HPGC. The experimental results showed that high volumes of HPG weakened the mechanical properties of HPGM and HPGC, while appropriate amounts of mineral admixtures offset the negative effects caused by calcium hydroxide (Ca(OH)₂) crystals and impurities within the system. The simulation results indicated that the maximum deviation between the mesoscale model prediction and experimental data was only 8.38%, which verified the accuracy of the mesoscale model prediction. The compressive strength of HPGC initially decreased and subsequently increased with the rise in the modulus and content of coarse aggregate, whereas it declined with higher HPG dosage and increased ITZ thickness. In contrast, the elastic modulus of HPGC showed a gradual increase with rising coarse aggregate content and improved ITZ mechanical properties, while it decreased as HPG content and ITZ thickness increased. Full article

Hyperspectral video acquisition requires a precise balance between spectral and temporal resolution, often achieved through compressive sampling using two-dimensional detectors and spectral reconstruction algorithms. However, the reliance on spatial light modulators for coding reduces optical efficiency, while complex recovery algorithms hinder real-time reconstruction. To address these challenges, we propose a digital-micromirror-device-based complementary dual-channel hyperspectral (DMD-CDH) video imaging system. This system employs a DMD for simultaneous light splitting and spatial encoding, enabling one channel to perform non-aliasing spectral sampling at lower frame rates while the other provides complementary high-rate sampling for panchromatic video. Featuring high optical throughput and efficient complementary sampling, the system ensures reliable hyperspectral video reconstruction and serves as a robust ground-based validation platform for remote sensing applications. Additionally, we introduce tailored optical error calibration and fixation techniques alongside a lightweight hyperspectral fusion network for reconstruction, achieving hyperspectral frame rates exceeding 30 fps. Compared to the existing models, this system simplifies the calibration process and provides a practical high-performance solution for real-time hyperspectral video imaging. Full article

This study seeks to improve the performance of a low-temperature differential free-piston Stirling air conditioner (FPSAC). To achieve this, a novel approach is proposed, which replaces the conventional simple harmonic drive with a multi-harmonic drive. This modification aims to optimize the motion of the driving piston, bringing it closer to the ideal movement pattern. The research involves both thermodynamic and dynamic coupling simulations of the FPSAC, complemented by experimental verification of its key performance parameters. A thermodynamic model for the gas medium, employing a quasi-one-dimensional dynamic approach for compressible fluids, and a nonlinear two-dimensional vibration dynamic model for the solid piston are developed, focusing on the low-temperature differential FPSAC physical model. The finite difference method is employed to numerically simulate the entire system, including the electromagnetic thrust of the multi-harmonic-driven linear oscillating motor, fluid transport equations, and the nonlinear dynamic equations of the power and gas control pistons. Variations in displacement, velocity, and pressure for each control volume at any given time are obtained, along with the indicator and temperature–entropy diagrams after the system stabilizes. The simulation results show that, in cooling mode, assuming no heat loss or mechanical friction, the Stirling cooler operates at a frequency of 80 Hz. Using the COP_sin value for the simple harmonic drive as a baseline, performance is improved by altering the driving method. Under the multi-harmonic drive, the COP_c5 increased by 10.03% and COP_c7 by 14.23%. In heating mode, the COP under the multi-harmonic drive improved by 0.51% for COP_h5 and 2.61% for COP_h7. Performance experiments were conducted on the low-temperature differential FPSAC, and the key parameter test results showed good agreement with the simulation outcomes. The maximum deviation at the trough was found to be less than 2.45%, while at the peak, the maximum error did not exceed 3.61%. When compared to the simple harmonic drive, the application of the multi-harmonic drive significantly enhances the overall efficiency of the FPSAC, demonstrating its superior performance. The simulation analysis and experimental results indicate a significant improvement in the coefficient of performance of the Stirling cooler under the multi-harmonic drive at the same power level, demonstrating that the multi-harmonic drive is an effective approach for enhancing FPSAC performance. Furthermore, it should be noted that the method proposed in this study is applicable to other types of low-temperature differential free-piston Stirling air conditioners. Full article

Recent research has shown the potential of polyhydroxyalkanoates (PHAs), particularly poly(3–hydroxybutyrate) (P3HB), to form nonwoven structures with fine fiber diameter distributions ranging from 2.5 µm to 20 µm during the meltblow process. The shortcomings of existing fabrics of this type include high brittleness, low elongation at break (max. 3%), and a lack of flexibility. Furthermore, the high melt adhesion and the special crystallization kinetics of PHAs have commonly been regarded as constraints in filament and nonwoven processing so far. However, these two properties have now been used to elaborate a three-dimensional fiber arrangement on a matrix, resulting in the creation of dimensionally and temperature-stable “nonwoven-parts”. Moreover, this study investigated the PHA copolymer poly(3–hydroxybutyrate–co–3–hydroxyhexanoate) (PHBH), revealing a similar processability to P3HB and PHBV in the meltblow process. A significant increase in the (peak load) elongation in the machine direction was observed, reaching values between 5% and 10%, while the tensile strength retained unaltered. The addition of the bio-based plasticizer acetyltributylcitrate (ATBC) to PHBH resulted on an increase in elongation up to 15%. The three-dimensional fabric structure of PHBH exhibited complete resilience to compression, a property that differentiates it from both P3HB and PHBV. However, the addition of the plasticizer to P3HB did not lead to any improvements. This interesting array of properties results in moderate air permeability and hydrophobicity, leading to impermeability to water. Full article

The loofah sponge has a complex, three-dimensional, porous mesh fiber structure characterized by markedly low density and excellent vibration isolation properties. In this study, loofah sponges made from dried Luffa cylindrica were divided into two components: the core unit and the shell unit, which were further subdivided into five regions. Static compression performance tests and vibration isolation analysis were conducted on the loofah sponge and its individual parts. Scanning models of the loofah sponge were generated using the RX Solutions nano-CT system in France, and finite element analysis was performed using the ANSYS Workbench. This study focused on the vibration isolation performance of the loofah sponge, examining energy absorption and isolation, as well as the vibrational strength of its isolation performance. The goal was to explore the functions and vibration isolation mechanisms of its different components. The results demonstrated that the loofah sponge structure exhibits rigid–flexible coupling, with the coordinated action of multiple parts producing highly effective energy absorption and isolation of the vibration intensity effect. Specifically, the core unit of the loofah sponge provides the best isolation effect of axial vibration intensity, with an acceleration vibration transfer of −60 dB at 300 Hz. Furthermore, both the core and shell unit structures combine to provide multidirectional low-frequency vibration isolation. This study of the loofah sponge’s vibration isolation mechanism provides a theoretical foundation and new insights for the design of bionic low-frequency vibration isolation devices. Full article

High slopes with multi-layer weak interlayers are a type of special slope that tends to fail due to the unfavorable mechanical properties of interlayers. In this study, the influence of the position, length, diameter, and ratio of on-center spacing to the pile diameter on the stability of such slopes is investigated using the three-dimensional strength reduction elastoplastic finite element method. Based on a high slope with multi-layer weak interlayers, two models were created, and three states (an initial state, a state with a safety factor of 1.35, and a limit equilibrium state) were considered. The pile can improve slope stability when the it is located at the lower to lower-middle part of a high slope. The resistance effect no longer has a strengthening property if it exceeds a critical pile length (28 m and 30 m in the two models); 30 m was found to be the optimal pile length for the high slope. As the diameter increased, the safety factor increased from 1.38 (1.37) to 1.41 (1.40) in Model 1 (or in Model 2), while the maximum compressive stress, the maximum shear stress of the pile, and the maximum displacement of the pile head decreased in the two models from 20.84 (81.24) MPa to 16.15 (18.8) MPa, 11.19 (42.02) MPa to 7.77 (10.43) MPa, and 714.1 (4585.00) mm to 396.3 (1272.00) mm, respectively. The pile diameter should be >1.4 m in such cases. When stress and displacement increased, the arching effect and the pile group effect weakened, and the safety factor decreased as the ratio of on-center spacing to diameter increased. The ratio should be <3 to ensure slope ability. Full article

With the depletion of fossil fuels, more and more green products are appearing in daily necessities. Bamboo is a common sustainable biomaterial with the characteristics of fast growth, easy bending, low cost, and easy processing, and it is widely used in furniture design. However, the poor aging resistance and UV resistance of natural bamboo materials limit their application in outdoor furniture. In order to improve the service life of outdoor bamboo furniture, this study prepared bamboo boards from bamboo powder and utilized them in the design of outdoor furniture. The research was conducted in two stages. In the first stage, functional modification was carried out on the surface of bamboo fibers (BF). Epoxy resin and UV absorber ZnO were introduced into the bamboo powder matrix, and a three-dimensional network structure of bamboo powder-based polymer material was formed by adjusting the material ratio and reaction conditions. With the increase of ZnO content, the absorption of moisture by the bamboo powder-based polymer materials decreased. The compressive strength of 1.5%ZnO-Board reached 36.8 MPa, exceeding the compressive strength of C30 concrete. In the second stage, 1.5% ZnO-Board was selected for solidification and demolding, and used as the seat surface for outdoor chairs. Through the car crushing experiment, the chair panel did not undergo significant deformation during the car crushing process. The anti-aging experiment showed that the structure and morphology of the panel would not be damaged by long-term UV irradiation. The panel did not show any weight changes in the anti-water-absorption experiment. By using low-contrast color combinations, the seats can be organically integrated into the environmental background, effectively enhancing the coordination and unity of the overall aesthetic harmony of the space. Compared with the commonly used plastic outdoor seats, the outdoor seats prepared in this study showed a 144% increase in carbon reduction effect. This study highlights the potential of modified bamboo powder for the design of outdoor furniture, which is of great significance to reducing outdoor plastic products and promoting sustainable life. Full article