Search Results (9,464)

We report on tool wear and surface roughness for hybrid additive manufacturing of Inconel 718 components. The hybrid additive manufacturing comprises laser powder bed fusion (PBF-LB/M) and an in situ high-speed milling process, i.e., milling is performed within the powderbed, which deteriorates the surface quality by additionally occurring wear mechanisms. Therefore, in this comparative study milling path suction is used to improve tool wear characteristics and thus enhance surface quality. As a result, we quantify the improvement of the maximum tool life according to the flank wear, which is granted by the milling path suction. Additionally, the dominant wear mechanisms are investigated, revealing adherence and abrasion as the main contributing factors to wear. Furthermore, surface analysis shows an improvement of surface quality by the use of the milling path suction. Specifically, a reduction in surface roughness of hybrid manufactured Inconel 718 components down to a minimum of $Ra$ = 0.55 μm is highlighted. Full article

In this note, we study the Hopf-algebra-based (HAB) formula of Yang–Mills-Scalar (YMS) amplitudes, which expands a YMS amplitude with massive scalars as a combination of propagator matrices that mix massless scalars corresponding to gluons with the original massive scalars. We propose a recursive formula that conveniently expresses the HAB formula. In this formula, gluons are converted into massless scalars. Thus it expresses a YMS amplitude with massive scalars by amplitudes with fewer gluons, massive scalars and massless scalars. We verify this formula by using the soft behavior of amplitudes. We further show the equivalence between the massless limit of the HAB formula and an earlier proposed recursive expansion formula through explicit calculations on amplitudes with one and two gluons. Full article

Brazil, as one of the world’s leading fruit producers, faces increasing challenges arising from climate change, particularly in avocado cultivation, where excessive solar radiation and high temperatures impair plant metabolism, yield, and fruit quality. This study evaluated the use of a calcium and magnesium hydroxide-based sunscreen in mitigating heat stress in eight-year-old ‘Hass’ avocado trees. The experimental design was a randomized complete block design in a 4 × 8 factorial arrangement, with five replicates. Sunscreen applications were performed at full bloom and at the initial fruit development stage (18 mm). Leaf temperature, fruit drop rate, yield-related traits, fruit classification, and the percentage of fruit lesions were evaluated. Applications of the calcium and magnesium hydroxide-based sunscreen at concentrations of 3.0% and 4.5% (w/v) reduced leaf temperature and improved fruit biometric attributes compared to the control, although the maximum fruit diameter was achieved at the 2.6% concentration. The 4.5% sunscreen concentration reduced leaf temperature and fruit drop in ‘Hass’ avocado trees by 1.5 °C and 24.5%, respectively, compared with the control and decreased the percentage of small and damaged fruits. The application of sunscreen improved fruit weight and the percentage of fruits with higher market value, while the fruit diameter presented higher values at intermediate concentrations. Full article

Background and aim: The influence of fabrication techniques, cement type, and cyclic loading on the marginal adaptation of lithium disilicate crowns remains a clinical concern that may affect their long-term performance. This study aimed to evaluate the effects of cyclic loading and cement type on the marginal fit of milled and pressed lithium disilicate crowns. Methods: Twenty lithium disilicate crowns were fabricated and divided into two groups based on the manufacturing technique: milled and pressed (n = 10 each). Each group was further subdivided according to the cement type: resin or resin-modified glass ionomer (n = 5 per group). Crowns were cemented on standardized epoxy resin dies, and the marginal gap was measured using a stereomicroscope before and after cyclic loading. Cyclic loading was performed at 50 N for 37,000 cycles. Data were statistically analyzed using a three-way ANOVA (α = 0.05). Results: Milled crowns showed marginal gaps ranging from 52 to 57 µm, whereas the pressed crowns exhibited smaller gaps ranging from 39 to 47 µm. Neither the cement type nor the cyclic loading produced a significant difference in the marginal gap values (p > 0.05). Conclusions: Pressed lithium disilicate crowns exhibited superior marginal adaptation compared with the milled crowns. Neither the type of cement nor the cyclic loading had a significant effect on the marginal gap. Both fabrication techniques yielded clinically acceptable fits (<100 µm). Full article

The preventive maintenance (PM) of asphalt pavements reduces life-cycle costs and minimizes resource consumption compared with reactive rehabilitation, yet its cost-effectiveness is highly sensitive to application timing. This study develops a data-driven framework for determining optimal PM timing on Korean expressways by integrating network-level pavement management system (PMS) deterioration modeling with life-cycle cost analysis (LCCA). Using 10-year PMS time-series data from approximately 2200 asphalt pavement sections (2012–2021), a nonlinear regression of the Highway Pavement Condition Index (HPCI) yielded an exponential deterioration model with exponent β = 1.87 (R² = 0.996), confirming accelerating deterioration beyond a critical service age. The HPCI inflection coincides with the Grade-2 boundary (3.5–4.0), where surface distress growth—dominated by linear cracking (91.3% of total SD)—also peaks. A LCCA across 44 scenarios demonstrated that PM applied immediately before this acceleration onset minimizes the 40-year net present value (NPV; discount rate 4.5%). The optimal first PM application time was estimated at 10.8 years (≈56% of the 19.3-year average service life), reducing the 40-year NPV by up to 7 million KRW per section relative to the milling and overlay baseline (up to 16 million KRW in absolute NPV terms for concrete overlay sections). These findings provide a quantitative, reproducible basis for PM timing decisions applicable to the approximately 4000 km of expressway pavement managed by Korea Expressway Corporation. Full article

High-performance cutting materials are central to modern production engineering. Cemented carbides dominate industrial tooling, while polycrystalline boron nitride (PcBN) is established for hard turning and finishing nickel-based alloys. The associated tool manufacturing chains are energy- and effort-intensive, motivating approaches that reduce material losses and primary energy demand. This study quantifies energy consumption across the production of solid carbide cutting tools with a focus on near-net-shape green machining, its impact on subsequent grinding and material recirculation. It also quantifies energy consumption for regrinding PcBN cutting tools. Power measurements were recorded during green machining and tool grinding of cylindrical versus pre-contoured (green-machined) blanks, including coolant units for the carbide tools during operation. Tool performance of the carbide tools was assessed via milling tests in 42CrMo4; PcBN reground tools were evaluated in Inconel 718. In the process chain of carbide tool production, specific energy decreased from 6.98 to 6.36 kWh/kg (−8.88%) despite +0.461 kWh/kg for green machining; direct recirculation of green-machined material saved an additional 5.861 kWh/kg. Reground PcBN inserts achieved comparable tool life to new tools while reducing energy by ≈85% per insert. The dominant levers for energy reduction are shorter grinding times in the presence of high machine and coolant base loads and systematic regrinding of high-embodied-energy tools. Full article

Tool wear remains a critical limiting factor in machining performance, particularly in dry cutting conditions where friction and tribological interactions dominate. This study investigates the influence of a 5–8 μm PVD-deposited TiN coating on the wear behavior of high-speed steel (HSS) end mills during milling of three representative wood species (oak, beech, and fir). A spatially resolved wear evaluation methodology was employed, based on ten measurement points distributed along a 20 mm active cutting edge, enabling simultaneous assessment of mean wear and maximum localized wear (Umax). A factorial experimental design combining material type and feed rate (1500–2500 mm/min) was analyzed using two-way ANOVA with effect size quantification (η²). The results reveal a statistically significant reduction in mean wear for TiN-coated tools (F = 7.46, p = 0.0195, η² = 0.34), corresponding to an average decrease of approximately 46% compared to uncoated tools. Maximum wear was influenced by both coating (F = 14.73, p = 0.0028, η² = 0.399) and material (F = 4.37, p = 0.040, η² = 0.237). The experimental findings are interpreted through a tribological framework, indicating a transition from abrasion- and micro-chipping-dominated degradation in uncoated tools to a controlled wear regime in TiN-coated tools, characterized by reduced asperity penetration, delayed crack initiation, and limited tribochemical interactions. These results demonstrate that coating effects dominate global wear evolution, while material properties influence localized degradation. The proposed combined experimental–statistical–mechanistic approach provides a robust framework for understanding and optimizing tool performance in dry machining environments. Full article

Surface quality of machined wood-based panels plays a key role in subsequent processing and product performance; however, its formation during CNC edge milling remains insufficiently understood, particularly for materials with different structural characteristics, including recycled content. This study investigates the influence of feed per tooth, milling strategy, and material structure on surface quality during CNC edge milling of particleboards manufactured from alternative lignocellulosic resources. Six board variants were experimentally produced and machined on a five-axis CNC machining center Morbidelli m100 using a single-edge milling cutter, with feed per tooth varied at three levels and both climb and conventional milling strategies applied. Surface quality was evaluated using a non-contact 3D optical profilometer Keyence VR-6000, and roughness (R_a) and waviness (W_z) parameters were analyzed. The results showed that surface roughness increased with increasing feed per tooth for all materials, with an increase of approximately 30%–70%. Statistical analysis confirmed a significant effect of feed per tooth and material type, while milling strategy and its interaction with material were not statistically significant. Materials with higher surface heterogeneity (CVR_a) showed increased roughness and greater sensitivity to feed. A statistically significant positive relationship was found between surface heterogeneity (CVR_a) and roughness sensitivity (ΔR_a), indicating that materials with higher surface heterogeneity (CVR_a), which likely reflects variability in their internal structure, are more sensitive to changes in feed per tooth. Full article

This paper addresses the stability and stabilization problems of rolling mill main drive systems with time delay. The complete stability problem with respect to the delay parameter is investigated for linearized systems with and without control. The systems are first formulated in the characteristic function form, and the corresponding complete stability problem is introduced. By employing the frequency-sweeping approach, the complete stability properties are systematically analyzed. As a result, several analytical properties related to the local asymptotic behavior of critical imaginary roots are derived. Finally, numerical examples demonstrate that the whole stability set with respect to delay can be accurately determined. Full article

Growing concerns over food waste and the increasing demand for gluten-free products highlight the need for sustainable food innovations. This study investigated the valorization of tomato processing by-products as functional ingredients in gluten-free crackers. Tomato by-products were dehydrated, milled into powder, and incorporated into cracker formulations at 10%, 20%, and 30% (w/w). The crackers were evaluated for bioactive compound content (lycopene, total carotenoids, and total phenolics), antioxidant activity (DPPH radical scavenging), and sensory acceptability using a 5-point hedonic test with 50 consumers. Increasing the level of tomato by-product incorporation significantly enhanced the nutritional profile of the crackers. Lycopene content increased from 0.65 mg/100 g in the control to 9.43 mg/100 g at 30% enrichment, while total phenolic content increased from 52.60 to 154.76 mg GAE/100 g. Sensory evaluation indicated that the 10% enrichment achieved the highest overall acceptability score, whereas higher enrichment levels resulted in slightly reduced taste preference. These findings demonstrate that tomato by-products can be effectively used to improve the nutritional quality of gluten-free crackers while maintaining acceptable sensory properties at moderate enrichment levels, supporting the sustainable valorization of tomato processing residues. Full article

Robotic milling offers flexibility and lower capital cost than conventional CNC machining but is limited by low, pose-dependent structural stiffness. This study experimentally investigates how pose, cutting orientation, and engagement conditions govern dynamic response and machining accuracy, benchmarked against a CNC machine under matched conditions. Tool-point frequency response functions show that the robot exhibits dominant low-frequency structural modes at 8–15 Hz with compliances on the order of 10⁻⁵ m/N, one to two orders of magnitude more flexible than higher-frequency tool–holder modes (~10⁻⁶ m/N). In contrast, the CNC system is dominated by a stiff mode near 600 Hz (~2 × 10⁻⁷ m/N) with negligible low-frequency compliance. During cutting, the response is not resonance-driven; instead, low-frequency compliance induces modulation of spindle-synchronous vibrations, resulting in broadband spectral spreading and cycle-to-cycle variability. Poincaré analysis captures this modulation, which increases with spindle speed and depth of cut. Orientation-dependent alignment with compliant directions amplifies vibration and cross-axis coupling. Regression analysis shows a significant association between Z-direction vibration and depth-of-cut deviation (R = 0.739 locally; R = 0.363 globally). The results establish a framework linking compliance, modulation, and machining performance in robotic milling. Full article

This study evaluates the potential of marc, a by-product of clitoria (Clitoria ternatea L.) and borage (Borago officinalis L.) infusions, as a preliminary step toward their subsequent conversion into functional food ingredients. After infusion, the marc was collected and processed by carrier-assisted crushing, aqueous maceration, and subsequent separation into extract and residue fractions. The impact of flower pretreatment by milling and marc matrix modification by inulin and maltodextrin was studied on the physical (dry matter (DM), water activity, color), chemical (total phenolic content (TPC), sum of individual phenolic compounds, and antioxidant capacity), and solubility of the microencapsulated fractions. Inulin-formulated powders derived from intact flowers’ marc were characterized by higher dry matter, decreased water activity, and improved chemical profiles. Under these conditions, clitoria by-products exhibited mean dry matter 94.17 ± 0.20%, water activity 0.301 ± 0.003, TPC 3.285 ± 0.052 mg GAE/g DM, sum of individual phenolic compounds 6.267 ± 0.103 mg/g DM, and ABTS-determined antioxidant capacity 0.100 ± 0.001 mmol Trolox/g DM. For borage by-products under identical conditions, dry matter content (−1.60%), water activity (−12.62%), TPC (−39.82%), sum of individual phenolic compounds (−67.55%), and antioxidant capacity (−65.00%) were lower compared with clitoria by-products. An efficient extraction and stabilization approach can open opportunities for upcycling post-extraction herbal residues into high-value food ingredients. Full article

Pruning residues from medicinal and aromatic plant cultivations represent an under-exploited biomass rich in bioactive metabolites. In this study, pruning by-products from Lavandula angustifolia Mill. ‘Essence Purple’ and Helichrysum italicum (Roth) G.Don were investigated as sources of essential oils (EOs) within a circular economy perspective. Micromorphological analyses confirmed the presence of secretory glandular trichomes in the residual biomass. EOs were obtained by steam distillation (0.33% and 0.15% yield for lavender and helichrysum, respectively) and chemically characterized by GC-FID and GC-MS. A total of 51 and 55 compounds were identified, accounting for 99.68% and 99.57% of the total composition. The main constituents were τ-cadinol (23.09%) and linalyl acetate (14.07%) in lavender EO and γ-curcumene (15.47%) and eudesm-4(14)-en-11-ol (10.71%) in helichrysum EO. Pruning-derived EOs showed a higher sesquiterpene content than those from conventional plant organs, indicating a compositional shift. Phytotoxic assays on Hordeum vulgare, Raphanus sativus, Lolium multiflorum, and Sinapis alba revealed concentration-dependent effects, with a stronger inhibition of radicle elongation than seed germination. These concentrations should be interpreted as indicative of intrinsic phytotoxic potential under controlled conditions. Ecotoxicological tests showed no significant reduction in viability in Artemia salina, whereas concentration- and time-dependent immobilization was observed in Daphnia magna, highlighting species-specific sensitivity, likely related to differences in the uptake and membrane interactions of lipophilic compounds. These findings highlight pruning residues as a promising biomass for the recovery of bioactive phytocomplexes with potential applications in sustainable weed management, although further studies under agronomically relevant conditions and comprehensive environmental assessments are required to validate their practical applicability. Full article

Invasive plant species are increasingly recognized not only as ecological threats but also as potential sources of bioactive compounds with agricultural applications. However, the combined allelopathic and insecticidal potential of Ailanthus altissima’s different plant parts remains insufficiently explored. This study evaluated the bioactivity of different plant part (leaf, bark, and branch) extracts of A. altissima. Secondary metabolites were characterized by HPLC–DAD–MS, while ethanol extracts (0.5–5%) were tested on wheat (Triticum aestivum) seed germination, seedling growth, oxidative status, and on the survival and repellency of the rice weevil (Sitophilus oryzae). Biological responses were strongly plant part and concentration-dependent. Leaf extracts contained the highest phenolic levels, dominated by caffeoylquinic acids and quercetin derivatives, whereas bark and branch extracts showed lower but compositionally distinct profiles. Despite this, bark and branch extracts produced the strongest biological effects, inhibiting germination energy and root growth at higher concentrations, while leaf extracts stimulated seedling performance, including increased vigor index, while in insect bioassays, bark and branch extracts caused higher mortality and stronger suppression of rice weevil populations. This study provides new evidence that biomass extracts of the invasive species A. altissima represent a promising source of biologically active compounds with both allelopathic and insecticidal properties, highlighting its potential valorization as a plant-based biopesticide for sustainable pest management. Full article

The present study examined the interactions between the structure, microstructure and mechanical properties of CrMnFeCoNi, CrMnFeCoNiV_0.5 and CrMnFeCoNiMo_0.5 High-Entropy Alloys (HEAs). Starting from elemental powders, the HEAs were obtained by high-energy ball milling, followed by vacuum annealing at 1373 K for 1 h. After milling, a binary FCC-BCC solid solution was formed; the samples showed hardness values ranging from 800 to 973 HV. Evidence shows that annealing HEAs reduced the solubility of V and Mo in the alloys’ FCC structure. Additionally, the Cr content in the FCC phase also decreases. The carbon derived from the decomposition of the process control agent was trapped in the interstices of the HEA structure during mechanical alloying. This amount of carbon is sufficient to form carbides during annealing. The thermodynamic stability of the precursor elements in HEAs is a determining factor in M_xC_y-type formation. The hardness response of HEAs was associated with the HEAs’ structure, while the elastic modulus was affected by their microstructure. Full article