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Search Results (211)

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40 pages, 6841 KiB  
Article
Distributionally Robust Multivariate Stochastic Cone Order Portfolio Optimization: Theory and Evidence from Borsa Istanbul
by Larissa Margerata Batrancea, Mehmet Ali Balcı, Ömer Akgüller and Lucian Gaban
Mathematics 2025, 13(15), 2473; https://doi.org/10.3390/math13152473 (registering DOI) - 31 Jul 2025
Abstract
We introduce a novel portfolio optimization framework—Distributionally Robust Multivariate Stochastic Cone Order (DR-MSCO)—which integrates partial orders on random vectors with Wasserstein-metric ambiguity sets and adaptive cone structures to model multivariate investor preferences under distributional uncertainty. Grounded in measure theory and convex analysis, DR-MSCO [...] Read more.
We introduce a novel portfolio optimization framework—Distributionally Robust Multivariate Stochastic Cone Order (DR-MSCO)—which integrates partial orders on random vectors with Wasserstein-metric ambiguity sets and adaptive cone structures to model multivariate investor preferences under distributional uncertainty. Grounded in measure theory and convex analysis, DR-MSCO employs data-driven cone selection calibrated to market regimes, along with coherent tail-risk operators that generalize Conditional Value-at-Risk to the multivariate setting. We derive a tractable second-order cone programming reformulation and demonstrate statistical consistency under empirical ambiguity sets. Empirically, we apply DR-MSCO to 23 Borsa Istanbul equities from 2021–2024, using a rolling estimation window and realistic transaction costs. Compared to classical mean–variance and standard distributionally robust benchmarks, DR-MSCO achieves higher overall and crisis-period Sharpe ratios (2.18 vs. 2.09 full sample; 0.95 vs. 0.69 during crises), reduces maximum drawdown by 10%, and yields endogenous diversification without exogenous constraints. Our results underscore the practical benefits of combining multivariate preference modeling with distributional robustness, offering institutional investors a tractable tool for resilient portfolio construction in volatile emerging markets. Full article
(This article belongs to the Special Issue Modern Trends in Mathematics, Probability and Statistics for Finance)
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15 pages, 1846 KiB  
Article
Synthesis of Monothiacalix[4]arene Using the Fragment Condensation Approach
by Daniel Kortus, Oliver Moravec, Hynek Varga, Michal Churý, Kamil Mamleev, Jan Čejka, Hana Dvořáková and Pavel Lhoták
Molecules 2025, 30(15), 3145; https://doi.org/10.3390/molecules30153145 - 27 Jul 2025
Viewed by 206
Abstract
The article describes a simple and scalable preparation of 2-monothiacalix[4]arene 7, the simplest representative of the mixed-bridged (CH2 and S) calix[4]arenes. The synthesis is based on the condensation of linear building blocks (bisphenols), which are relatively readily available, and allows, depending [...] Read more.
The article describes a simple and scalable preparation of 2-monothiacalix[4]arene 7, the simplest representative of the mixed-bridged (CH2 and S) calix[4]arenes. The synthesis is based on the condensation of linear building blocks (bisphenols), which are relatively readily available, and allows, depending on the conditions, the use of two alternative reaction routes that provide macrocycle 7 in high yield. The dynamic behavior of the basic macrocyclic skeleton was investigated using NMR spectroscopy at variable temperatures. High-temperature measurements showed that compound 7 undergoes a conecone equilibrium with activation free energy ΔG# of the inversion process of 63 kJ·mol−1. Interestingly, the same barrier for the oxidized sulfone derivative 14 shows a value of 60 kJ·mol−1, indicating weakened hydrogen bonds at the lower rim of the calixarene. The same was also confirmed at low temperatures, when barriers to changing the direction of the cyclic hydrogen bond arrays (flip-flop mechanism) were determined (compare ΔG# = 44 kJ·mol−1 for 7 vs. ΔG# = 40 kJ·mol−1 for 14). Full article
(This article belongs to the Special Issue Organosulfur and Organoselenium Chemistry II)
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12 pages, 1153 KiB  
Article
Estimating Molar Root Volume from Panoramic Radiographs Using a Geometric Approach—An Experimental Method Comparison
by Katharina Hartmann, Markus Tröltzsch, Sven Otto and Matthias Tröltzsch
Medicina 2025, 61(7), 1261; https://doi.org/10.3390/medicina61071261 - 11 Jul 2025
Viewed by 282
Abstract
Background and Objectives: Evaluating jaw augmentation procedures usually necessitates pre- and postoperative tomographic imaging. Ethical considerations emphasize minimizing radiation exposure. Given that panoramic radiographs (PR, 2D) offer a lower radiation dose compared to cone-beam CT (CBCT, 3D), this study explores the feasibility [...] Read more.
Background and Objectives: Evaluating jaw augmentation procedures usually necessitates pre- and postoperative tomographic imaging. Ethical considerations emphasize minimizing radiation exposure. Given that panoramic radiographs (PR, 2D) offer a lower radiation dose compared to cone-beam CT (CBCT, 3D), this study explores the feasibility of estimating tooth root volume from PR, potentially allowing safer clinical assessments with reduced radiation exposure. Materials and Methods: To develop a mathematical approximation method, the 2D tooth root surface in PR was defined as an elliptical model and a cuboid (3D). The true root volume (mm3) was gathered from CBCTs. The missing link for tooth root volume assessment in 2D radiographs is the depth of the root (vestibulo-oral dimension). It was hypothesized that the tooth root surface and its volume are related. A correlation factor “r” corresponding to the tooth roots’ depths was then calculated. Descriptive and inferential statistics were computed (p < 0.05). Results: The mathematical model was performed on 27 molars with an average volume of 472.83 mm3 (±130.25–CBCT). The factor “r” (obtained by dividing the true root volume from CBCT by the total root surface from PR) was computed as 8.04 (±1.90). Using “r” for the volume calculation in the cuboid model, an average volume of 472.37 (±152.92) for the 27 molars was computed. These volumes did not differ significantly. Conclusions: This study demonstrates that a mathematical model using elliptical projections from panoramic radiographs reliably estimates molar root volume, yielding comparable results to CBCT while reducing radiation exposure. Full article
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20 pages, 800 KiB  
Article
The Influence of Plant Growth Regulators (PGRs) on Physical and Chemical Characteristics of Hops (Humulus lupulus L.)
by Mengzi Zhang, Nicholas A. Wendrick, Sean M. Campbell, Jacob E. Gazaleh, Heqiang Huo, Katherine A. Thompson-Witrick and Brian J. Pearson
Int. J. Plant Biol. 2025, 16(3), 79; https://doi.org/10.3390/ijpb16030079 - 8 Jul 2025
Viewed by 353
Abstract
Hops (Humulus lupulus L.) are a critical component in beer brewing. The growing demand for craft beer has increased interest in hop cultivation in non-traditional regions where unfavorable climatic conditions hinder optimal yield and quality. To address these challenges, this study investigates [...] Read more.
Hops (Humulus lupulus L.) are a critical component in beer brewing. The growing demand for craft beer has increased interest in hop cultivation in non-traditional regions where unfavorable climatic conditions hinder optimal yield and quality. To address these challenges, this study investigates the effects of plant growth regulators (PGRs) on hop cone yield and chemical compositions. In two separate studies, year-1 Cascade hops were subjected to various PGR treatments in the field. PGR treatments generally had minimal effect on the dry cone yield in study I. In study II, a combination of Ethephon at 45 mg/L and ProGibb at 3 mg/L significantly increased the cone yield by 125% compared to the control. While all treatments had a “good quality” hop storage index, a combination of Ethephon and ProGibb produced alpha acid percentages within the commercial standard range. Ethephon at 30 mg/L combined with ProGibb at 2 mg/L enhanced bitterness and aroma, delivering the highest concentration of volatile organic compounds at 569.7 mg/L, thereby enhancing aroma compounds associated with fruity esters, monoterpenes, and sesquiterpenes. This study demonstrates that specific PGR treatments can improve the chemical composition of hops grown in non-traditional regions, with implications for optimizing aroma and bitterness in beer. Full article
(This article belongs to the Section Plant Physiology)
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13 pages, 2837 KiB  
Article
Voxel Size and Field of View Influence on Periodontal Bone Assessment Using Four CBCT Systems: An Experimental Ex Vivo Analysis
by Victória Geisa Brito de Oliveira, Polyane Mazucatto Queiroz, Alessandra Rocha Simões, Mônica Ghislaine Oliveira Alves, Maria Aparecida Neves Jardini, André Luiz Ferreira Costa and Sérgio Lucio Pereira de Castro Lopes
Tomography 2025, 11(7), 74; https://doi.org/10.3390/tomography11070074 - 25 Jun 2025
Viewed by 331
Abstract
Objective: This ex vivo study aimed to evaluate the influence of different acquisition protocols, combining voxel size and field of view (FOV), across four cone-beam computed tomography (CBCT) systems, on the accuracy of alveolar bone level measurements for periodontal assessment. Materials and Methods: [...] Read more.
Objective: This ex vivo study aimed to evaluate the influence of different acquisition protocols, combining voxel size and field of view (FOV), across four cone-beam computed tomography (CBCT) systems, on the accuracy of alveolar bone level measurements for periodontal assessment. Materials and Methods: A dry human mandible was used, with standardized radiopaque markers placed on the cementoenamel junction (CEJ) of the buccal–mesial and buccal–distal aspects of teeth 34 and 43. CBCT scans were performed using four systems—Veraview® X800, OP300 Pro®, I-CAT Next Generation®, and Orthophos XG®—applying various combinations of field of view (FOV) and voxel resolution available in each device. Reference measurements were obtained in situ using a digital caliper. CBCT images were exported in DICOM format and analyzed with OnDemand3D software (version 4.6) to obtain paracoronal sections. Linear measurements from the CEJ to the alveolar crest were recorded in triplicate and compared to the gold standard using ANOVA and the Dunnett test (α = 0.05). Results: Protocols with smaller voxel sizes and limited FOVs generally yielded measurements closer to the gold standard. However, some larger-FOV protocols with intermediate voxel sizes also achieved comparable accuracy. Among the systems, the I-CAT showed lower agreement within in situ measurements, while others demonstrated reliable performance depending on the acquisition parameters. Conclusions: The findings suggest that CBCT protocols with smaller voxel sizes and reduced FOVs can enhance measurement accuracy in periodontal bone assessments. Nevertheless, intermediate protocols may offer a balance between diagnostic quality and radiation exposure, aligning with the ALADA principle. This study reinforces the need for standardized acquisition parameters tailored to periodontal imaging. Full article
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29 pages, 915 KiB  
Article
Measurement Along the Path of Unmanned Aerial Vehicles for Best Horizontal Dilution of Precision and Geometric Dilution of Precision
by Yanwu Ding, Dan Shen, Khanh Pham and Genshe Chen
Sensors 2025, 25(13), 3901; https://doi.org/10.3390/s25133901 - 23 Jun 2025
Viewed by 279
Abstract
In the zenith-horizon placement for achieving minimum geometric dilution of precision (GDOP), one access node or sensor is positioned along the z-axis, while the remaining nodes are placed symmetrically on a three-dimensional (3D) cone. This configuration yields the minimum GDOP at the cone’s [...] Read more.
In the zenith-horizon placement for achieving minimum geometric dilution of precision (GDOP), one access node or sensor is positioned along the z-axis, while the remaining nodes are placed symmetrically on a three-dimensional (3D) cone. This configuration yields the minimum GDOP at the cone’s tip, which we term the designated min-GDOP point. However, in practical localization applications, the unknown node is not necessarily located at this designated min-GDOP point; instead, it may be situated anywhere within an area. As a result, evaluating localization accuracy across the entire area, rather than at a single point, is more relevant. Averaged horizontal dilution of precision (HDOP) and GDOP across the region provide more meaningful metrics for system-wide performance than values computed only at a specific location. Although many recent positioning applications leverage multiple unmanned aerial vehicles (UAVs), many established fixed sensor deployments predate the widespread adoption of UAVs. This paper proposes a novel approach with a single UAV working in conjunction with existing fixed access nodes for positioning. This approach offers improved adaptability for fixed infrastructure while circumventing the expense of establishing entirely new UAV systems, thus providing a valuable compromise. We investigate the criteria of average HDOP and GDOP over the given area. The objective is to determine optimal UAV positions along the flight path that minimize the average HDOP and/or GDOP across the area. Due to the analytical complexity, we employ numerical methods. Our simulation results demonstrate that minimizing average HDOP and GDOP often requires different UAV positions, depending on the number of access nodes and the size of the area. Consequently, achieving simultaneous minimization of both metrics with a single UAV trajectory is generally infeasible. When minimizing the average HDOP with a small number of access nodes, aligning the UAV’s XY-plane angle with those of the stationary nodes, offset by 60, proves advantageous. This angular alignment becomes less critical as the number of access nodes increases. For scenarios where both HDOP and GDOP are important, UAV placement can be optimized by selecting appropriate trade-offs. Additionally, we quantify how increasing the number of access nodes improves the average HDOP and GDOP over the specified area. Full article
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22 pages, 27621 KiB  
Article
Exploration of the Effects of Different Beauveria bassiana Strains on Dioryctria sylvestrella Larvae from the Perspective of Oxidative Stress
by Ruting Chen, Meiling Wang, Hanwen Zhang, Jianjiao Xu, Xiaomei Wang, Defu Chi and Jia Yu
Insects 2025, 16(6), 640; https://doi.org/10.3390/insects16060640 - 18 Jun 2025
Viewed by 612
Abstract
(1) Background: The larvae of Dioryctria sylvestrella typically bore into the shoots and cones of Pinus koraiensis, increasing tree breakage risk and reducing cone yield. (2) Methods: Five Beauveria bassiana strains were evaluated for virulence against fourth-instar larvae. And the levels of [...] Read more.
(1) Background: The larvae of Dioryctria sylvestrella typically bore into the shoots and cones of Pinus koraiensis, increasing tree breakage risk and reducing cone yield. (2) Methods: Five Beauveria bassiana strains were evaluated for virulence against fourth-instar larvae. And the levels of T-AOC and MDA in the larvae infected by each strain were measured. To assess larval responses to different strains, we measured the activities of six enzymes (SOD, CAT, POD, PPO, CarE, GST) and the levels of GSH and H2O2 in larvae treated with each strain. Additionally, the infection process of highly pathogenic B. bassiana in larvae was explored using scanning electron microscopy (SEM). (3) Results: Strain CGMCC3.2055 demonstrated the highest toxicity to larvae, achieving a cumulative corrected mortality of 80.56% on the 4th day and an LT50 of 3.248 days. The T-AOC of larvae treated with strain CGMCC3.2055 was inhibited within 48 h. The relative MDA content in this group was significantly higher than that in other strain-treated groups at 6, 12, and 24 h. In Bb01-treated larvae, H2O2 accumulation at 6 and 24 h post-infection was influenced by POD activity rather than GSH levels; in BbZ1-treated larvae, the activities of CAT and POD were upregulated at 6 and 36 h, while the activity of SOD was downregulated, but the content of H2O2 increased significantly, resulting in accumulation; in CFCC81428-treated larvae, a decline in T-AOC coincided with substantial H2O2 accumulation over 48 h, while a concomitant increase in GSH content bolstered tolerance to lethal oxidative damage; in CGMCC3.2055-treated larvae, H2O2 only accumulated significantly at 24 and 48 h, yet upregulated CAT and POD were insufficient to effectively scavenge the excess H2O2; and in bio-21738-treated larvae, SOD-driven dismutation generated substantial H2O2 from 12 to 48 h, leading to pronounced accumulation from 6 to 48 h, yet limited upregulation of POD (only at 6 and 12 h) and CAT (only at 12 and 48 h) were insufficient to mitigate H2O2 buildup. PPO activity was upregulated within 48 h in all treatment groups except for BbZ1, where no upregulation was observed at 12 and 48 h. GST activity was upregulated in all treatment groups except for CGMCC3.2055, where a downregulation was observed at 12 h post-infection. CarE activity was significantly upregulated within 48 h in both CFCC81428 and CGMCC3.2055 groups; in the Bb01 group, CarE was upregulated only at 6 and 48 h; in the BbZ1 group, CarE was downregulated only at 48 h; and in the bio-21738 group, CarE showed no upregulation at 24 and 48 h. Through SEM, the infection process of the strain CGMCC3.2055 on the surface of the larvae was further determined, which mainly included adhesion, the appearance of bud-like protrusions, the growth of germ tubes along the epidermis and penetration of the epidermis, as well as the colonization of the strain and its emergence from the surface of the larvae. (4) Conclusions: This study first screened the highly pathogenic B. bassiana strain CGMCC3.2055 by evaluating its virulence to larvae and post-infection T-AOC and MDA levels. It also clarified the strain’s infection process and the larvae’s immune responses to various strains. Full article
(This article belongs to the Section Insect Behavior and Pathology)
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12 pages, 308 KiB  
Article
Projected Gradient Descent Method for Tropical Principal Component Analysis over Tree Space
by Ruriko Yoshida
Mathematics 2025, 13(11), 1776; https://doi.org/10.3390/math13111776 - 27 May 2025
Viewed by 367
Abstract
Tropical Principal Component Analysis (PCA) is an analogue of the classical PCA in the setting of tropical geometry, and applied it to visualize a set of gene trees over a space of phylogenetic trees, which is a union of lower-dimensional polyhedral cones in [...] Read more.
Tropical Principal Component Analysis (PCA) is an analogue of the classical PCA in the setting of tropical geometry, and applied it to visualize a set of gene trees over a space of phylogenetic trees, which is a union of lower-dimensional polyhedral cones in an Euclidean space with dimension m(m1)/2, where m is the number of leaves. In this paper, we introduce a projected gradient descent method to estimate the tropical principal polytope over the space of phylogenetic trees, and we apply it to an Apicomplexa dataset. With computational experiments against Markov Chain Monte Carlo (MCMC) samplers, we show that our projected gradient descent method yields a lower sum of tropical distances between observations and their projections onto the estimated best-fit tropical polytope, compared with the MCMC-based approach. Full article
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9 pages, 722 KiB  
Article
Accuracy of Patient-Specific Osteosynthesis in Bimaxillary Surgery: Comparative Feasibility Analysis of Four- and Two-Miniplate Fixation
by Hylke van der Wel, Haye Glas, Johan Jansma and Rutger Schepers
J. Pers. Med. 2025, 15(5), 186; https://doi.org/10.3390/jpm15050186 - 4 May 2025
Viewed by 476
Abstract
Background/Objectives: Patient-specific osteosynthesis (PSO) plates, in combination with virtual surgical planning (VSP), have significantly improved the accuracy of orthognathic surgery. This study aimed to compare the surgical accuracy of two-plate versus four-plate fixation methods in Le Fort I osteotomies using PSO. Methods [...] Read more.
Background/Objectives: Patient-specific osteosynthesis (PSO) plates, in combination with virtual surgical planning (VSP), have significantly improved the accuracy of orthognathic surgery. This study aimed to compare the surgical accuracy of two-plate versus four-plate fixation methods in Le Fort I osteotomies using PSO. Methods: A retrospective cohort study was conducted on 21 patients who underwent maxilla-first bimaxillary surgery at a single centre in 2024. Eight patients received two-plate fixation, while thirteen received four-plate fixation. All surgeries were planned using VSP. Postoperative cone beam computed tomography scans were used to assess the accuracy of maxillary positioning by comparing the planned versus achieved outcomes in terms of translation and rotation. Results: Both fixation methods yielded comparable results in maxillary positioning, with no significant differences observed between the two groups regarding translational or rotational deviations. The two-plate PSO approach demonstrated practical benefits, including reduced material usage and the potential for smaller surgical incisions, without compromising surgical accuracy. Conclusions: Two-plate PSO fixation is a viable alternative to the traditional four-plate method for Le Fort I osteotomies, offering similar accuracy with potential procedural advantages. While these findings support broader clinical adoption, further research is warranted to confirm the results in larger cohorts and to investigate biomechanical considerations. Full article
(This article belongs to the Section Personalized Therapy and Drug Delivery)
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18 pages, 3813 KiB  
Article
Optimizing Dense Medium Separation Pre-Concentration by Comparative Evaluation of High-Pressure Grinding Rolls vs. Conventional Crushing
by Tebogo Mokgomola, Getrude Marape and Rabelani Mariba
Minerals 2025, 15(4), 422; https://doi.org/10.3390/min15040422 - 18 Apr 2025
Viewed by 502
Abstract
This paper investigated pre-concentration of a low-grade Upper Group 2 (UG2) ore to assess the possibility of rejecting waste at a typical discard Platinum Group Metals (PGMs) grade of <0.4 g/t at mass rejection to floats greater than 16% by comparing feed prepared [...] Read more.
This paper investigated pre-concentration of a low-grade Upper Group 2 (UG2) ore to assess the possibility of rejecting waste at a typical discard Platinum Group Metals (PGMs) grade of <0.4 g/t at mass rejection to floats greater than 16% by comparing feed prepared by High pressure grinding rolls (HPGR) to Conventional crushers (Cone crushers). Heavy Liquid Separation (HLS) was conducted as a benchmark test to Dense Medium Separation (DMS) to determine the expected grade, recovery, and mass yield for various size classes and crusher. The comparison between fine size classes −9.5 + 1.18 mm and −6.7 + 1.18 mm crushed by HPGR and conventional crushing showed that, under the conditions tested, the conventional crusher outperformed HPGR in terms of high sinks grade and a higher percentage of material exposed to pre-concentration. Looking at coarser size fractions (+12 mm), HLS results showed that under the conditions tested, size fraction −20 + 1.18 mm crushed by a conventional crusher at an optimum density of 3.4 g/cm3 is an optimized size fraction to run the DMS plant. The pilot DMS cyclone testwork showed that 61.1% by mass could be rejected to the floats stream based on Run of Mine (ROM) feed at 1.12% Cr2O3 and 0.42 g/t Total PGMs + Au grade, a typical discardable PGMs grade. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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13 pages, 2235 KiB  
Article
Optimization of DD-110 Neutron Generator Output for Boron Neutron Capture Therapy Using Monte Carlo Simulation
by Hossam Donya and Muhammed Umer
Quantum Beam Sci. 2025, 9(2), 12; https://doi.org/10.3390/qubs9020012 - 15 Apr 2025
Cited by 2 | Viewed by 1399
Abstract
Boron neutron capture therapy (BNCT) is a specialized cancer treatment that leverages the high absorption cross-section of boron for thermal neutrons. When boron captures neutrons, it undergoes a nuclear reaction that produces alpha particles and lithium ions, which have high linear energy transfer [...] Read more.
Boron neutron capture therapy (BNCT) is a specialized cancer treatment that leverages the high absorption cross-section of boron for thermal neutrons. When boron captures neutrons, it undergoes a nuclear reaction that produces alpha particles and lithium ions, which have high linear energy transfer (LET) and can effectively damage nearby cancer cells while minimizing harm to surrounding healthy tissues. This targeted approach makes BNCT particularly advantageous for treating tumors situated in sensitive areas where traditional radiation therapies may pose risks to critical structures. In this study, the deuterium–deuterium (DD) neutron generator, specifically the DD-110 model (neutron yield Y = 1 × 1010 n/s), served as the neutron source for BNCT. The fast neutrons produced by this generator were thermalized to the epithermal energy range using a beam-shaping assembly (BSA). The BSA was designed with a moderator composed of 32 cm of MgF2, a reflector made of 76 cm of Pb, and filters including 3 cm of Pb and 1.52 cm of Bi. A collimator, featuring a 10 cm high Pb cone frustum with a 12 cm aperture diameter, was also employed to optimize beam characteristics. The entire system’s performance was modeled and simulated using the MCNPX code, focusing on parameters both in-air and in-phantom to evaluate its efficacy. The findings indicated that the BSA configuration yielded an optimal thermal-to-epithermal flux ratio (φther/φepth) of 0.19, a current-to-flux ratio of 0.87, and a gamma dose-to-epithermal flux ratio of 1.71 × 10−13 Gy/cm2, all aligning with IAEA recommendations. The simulated system showed acceptable ratios for φther/φepth, gamma dose to epithermal flux, and beam collimation. Notably, the advantage depth was recorded at 5.5 cm, with an advantage ratio of 2.29 and an advantage depth dose rate of 4.1 × 10−4 Gy.Eq/min. The epithermal neutron flux of D110 exceeded D109, but D110’s fast neutron contamination increased ~6.6 times. On the other hand, D110’s gamma contamination decreased by 30%. Based on these findings, optimizing neutron source characteristics is crucial for BNCT efficacy. Future research should focus on developing advanced neutron generators that balance these factors, aiming to produce optimal neutron yields for enhanced treatment outcomes and broader applicability. Full article
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17 pages, 8236 KiB  
Article
Polyvinyl Alcohol Composite Films Containing Flame-Retardant DOPO-VTES and α-ZrP
by Jiayou Xu, Minyi Luo, Riyan Lin and Shu Lv
Polymers 2025, 17(8), 1011; https://doi.org/10.3390/polym17081011 - 9 Apr 2025
Viewed by 589
Abstract
Polyvinyl alcohol (PVA) is used in various fields; however, its highly flammable property greatly limits its application. In order to improve the flame-retardant properties of PVA, one method is by adding flame retardants directly, while another method is through grafting, cross-linking and hydrogen [...] Read more.
Polyvinyl alcohol (PVA) is used in various fields; however, its highly flammable property greatly limits its application. In order to improve the flame-retardant properties of PVA, one method is by adding flame retardants directly, while another method is through grafting, cross-linking and hydrogen bonding. A flame retardant, 9, 10-dihydro-9, 10-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-vinyltrimethoxysilane (VTES), was synthesized through the addition reaction of a P–H bond on the DOPO and unsaturated carbon–carbon double bonds on the VTES. Then, the DOPO-VTES and zirconium phosphate (α-ZrP) were blended with PVA to cast a film, in which DOPO-VTES was grafted onto the PVA by cross-linking the hydroxyl group in the molecular structure of DOPO-VTES with the hydroxyl group in PVA; α-ZrP was used as a cooperative agent of DOPO-VTES. The cone calorimetry test (CCT) showed a significant reduction in both the heat release rate (HRR) and total heat release rate (THR) for the flame-retardant PVA films compared to pure PVA. Additionally, thermogravimetric analysis (TGA) revealed a higher residual char content in the flame-retardant PVA films than in pure PVA. These findings suggested that the combination of DOPO-VTES and α-ZrP could improve the flame retardancy of PVA. The cooperative flame-retardant mode of action at play was possibly that DOPO in the DOPO-VTES acted as a mainly gas-phase flame retardant, which yielded a PO radical; VTES in the DOPO-VTES produced silicon dioxide (SiO2), which acted as a thermal insulator; and α-ZrP catalyzed the carbonization of the PVA. By combining DOPO-VTES with α-ZrP, a continuous dense carbon layer was formed, which effectively inhibited oxygen and heat exchange, resulting in a flame-retardant effect. It is expected that flame-retardant films for PVA have a broad development prospect and potential in the fields of packaging materials, electronic appliances, and lithium-ion battery separators. Full article
(This article belongs to the Special Issue Advances in Flame Retardant Polymeric Materials and Composites)
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20 pages, 8027 KiB  
Article
Time-Frequency Feature Extraction Method for Weak Acoustic Signals from Drill Pipe of Seafloor Drill
by Jingwei Xu, Buyan Wan, Weicai Quan, Yi Xi and Xianglin Tian
J. Mar. Sci. Eng. 2025, 13(4), 740; https://doi.org/10.3390/jmse13040740 - 8 Apr 2025
Viewed by 407
Abstract
The acoustic signals of the drill pipe of a seafloor drill present weak features under noise interference such as marine environmental noise and the mechanical vibration of the seafloor drill. Accurately extracting the features of the weak acoustic signals of a drill pipe [...] Read more.
The acoustic signals of the drill pipe of a seafloor drill present weak features under noise interference such as marine environmental noise and the mechanical vibration of the seafloor drill. Accurately extracting the features of the weak acoustic signals of a drill pipe under a strong background noise is an effective means of realizing wireless acoustic communication for a seafloor drill. However, the existing short-time Fourier transform and wavelet transform methods have the defects of fixed window length, wavelet basis function, and decomposition layers, which lead to the inability to accurately extract the weak acoustic signal features of a drill pipe. To overcome these challenges, this study investigates the application of S-transform (ST) in the weak acoustic signal feature extraction of a seafloor drill pipe based on its fundamental principles. Firstly, a time-frequency analysis of the drill pipe’s acoustic signal using ST is conducted, which yields the distribution of the signal across the time and frequency axes. Secondly, singular value decomposition (SVD) is applied to mitigate the noise within the time-frequency matrix. Finally, the noise-reduced time-frequency matrix is analyzed to extract the subtle features of the acoustic wave present within the signal. In order to more accurately assess the differences between the different time-frequency analysis methods in the extraction of weak acoustic wave signals, short-time Fourier transform, wavelet transform, and ST are used to extract the weak acoustic wave characteristics of the drill pipe, respectively. The results show that the ST-based method can effectively improve the accuracy of weak acoustic wave signal feature extraction and provide strong support for reliable transmission of cone penetration test data from the seafloor drill. Full article
(This article belongs to the Section Ocean Engineering)
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16 pages, 3088 KiB  
Article
Relationship Between Dynamics of Plant Biometric Parameters and Leaf Area Index of Hop (Humulus lupulus L.) Plants
by Václav Brant, Karel Krofta, Petr Zábranský, Pavel Hamouz, Pavel Procházka, Jiří Dreksler, Milan Kroulík and Gabriela Fritschová
Agronomy 2025, 15(4), 823; https://doi.org/10.3390/agronomy15040823 - 26 Mar 2025
Viewed by 470
Abstract
Biometric parameters of hop plants were studied over a three-year period on the Czech variety Premiant grown in the Žatec (Saaz) hop-growing region under an organic farming regime. Initially, only bine leaves developed, with lateral leaves emerging during the third growing month (June). [...] Read more.
Biometric parameters of hop plants were studied over a three-year period on the Czech variety Premiant grown in the Žatec (Saaz) hop-growing region under an organic farming regime. Initially, only bine leaves developed, with lateral leaves emerging during the third growing month (June). Their leaf area at the time of harvest was larger than the bine leaves. The moment when the area size of both leaf categories was the same, designated as the breaking point (BP), was determined in the interval 181–195 DOY (day of year). The leaf area (LA) measured using infrared imaging and gravimetric methods yielded comparable results, with correlation coefficients of 0.93 and 0.96, respectively. The total leaf area of one hop plant (LA) with four trained bines, which developed dynamically during ontogeny, was 10.45 m2 (2019), 6.65 m2 (2020), and 12.04 m2 (2021) in the harvest period. With a spacing of 3 m × 1 m, the corresponding Leaf Area Index (LAI) values were 3.5, 2.2 and 4.0 in the harvest season. Therefore, they are comparable to other crops such as maize or sorghum. Regression equations were calculated to determine the dry biomass of bine and lateral leaves depending on DOY. Correlations between the dry mass of leaves and the size of the leaf area for both bine and lateral leaves were also evaluated. This work also contains data on the mass proportions of the main plant organs (bine, leaves, cones). Full article
(This article belongs to the Section Horticultural and Floricultural Crops)
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13 pages, 2405 KiB  
Article
Development of Electrode of Electric Impulse Chamber for Coal Grinding
by Ayanbergen Kairbekovich Khassenov, Dana Zhilkibaevna Karabekova, Madina Muratovna Bolatbekova, Arystan Satybaldinovich Kudussov, Serik S. Kassymov and Lyubov Vasilyevna Chirkova
Appl. Sci. 2025, 15(7), 3607; https://doi.org/10.3390/app15073607 - 25 Mar 2025
Cited by 1 | Viewed by 324
Abstract
The coal industry remains a significant source of environmental pollution. Development of coal–water fuel allows for the reduction of harmful emissions (CO2, SO2, etc.) due to a more complete and environmentally friendly combustion of the fuel, making it an [...] Read more.
The coal industry remains a significant source of environmental pollution. Development of coal–water fuel allows for the reduction of harmful emissions (CO2, SO2, etc.) due to a more complete and environmentally friendly combustion of the fuel, making it an attractive transition solution towards cleaner energy. This study uses electropulse processing, which significantly increased the efficiency of the coal grinding process compared to mechanical action methods (cone mills, drum mills, etc.). The main advantages of electropulse technology are grinding efficiency, reduced high environmental impact (no need for chemical reagents and waste minimization), and the ability to produce coal powder with improved porosity and a larger surface area. The electrode in electropulse devices plays a decisive role in obtaining coal powder for coal–water fuel. The positive electrode must be resistant to high temperatures and aggressive conditions arising during the pulse processing. We have developed an optimal electrode design, including a gap between the metal rod and insulation, which ensures high resistance to pulse discharges. Increasing the capacity of the capacitor and the number of pulse discharges has had a positive effect on the yield of the finished product. The developed technology of electric impulse coal grinding helps to reduce the negative impact of the coal industry on the environment. Full article
(This article belongs to the Section Mechanical Engineering)
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