Search Results (1,545)

While shielding gas selection significantly impacts gas metal arc directed energy deposition (GMA-DED), current industrial practices often rely on ad hoc decisions. This study proposes a logical and reproducible selection methodology that prioritizes geometric outcomes (such as layer height, width, and surface waviness) for HSLA thin walls. The performance of three Argon-based blends was examined with the constraints of the same wire, contact tip-to-work distance, wire feed, and deposition speeds. However, to ensure a scientifically ‘fair comparison’ between gas blends, the methodology prioritized maintaining optimal metal transfer regularity for each composition by adjusting the proper voltage setting with a constant-voltage power source. Results showed that increasing CO₂ content requires higher arc voltage but lower average current to maintain a constant wire feed speed. This shift leads to shorter and wider layers, while lateral surface waviness remains largely unaffected by gas composition. The primary contribution of this work is the establishment of a multifaceted decision-making system that enables users to balance these geometric and operational outcomes against specific production goals. As a demonstration, an Ar + 8% CO₂ blend was successfully selected using a criterion that balances high productivity with low thermal stress, providing a justified alternative to conventional trial-and-error selection. Full article

The main aim of this study was to evaluate the applicability of a low-cost, double-wall gas metal arc welding (GMAW)-based wire arc additive manufacturing (WAAM) process for aluminum alloy AlMg5, with an emphasis on microstructural heterogeneity, layer-dependent defect formation, and their implications for mechanical performance and geometric characteristics. A Taguchi L9 (3³) design of experiments was employed to investigate the influence of welding current (40–60 A), shielding gas flow (10–20 L/min), and arc correction (0–40%) on wall geometry, material utilization, and overall process quality through multi-response optimization. The optimal parameter set (60 A, 15 L/min, 0% arc correction) resulted in a 54.9% improvement in the Grey Relational Grade compared to the lowest-performing configuration. Metallographic analysis revealed heterogeneous grain evolution governed by the multilayer thermal history, with porosity levels ranging from 3.20% to 3.49% and lack-of-fusion defects preferentially concentrated in interlayer and mid-height regions. The fabricated high-wall structure exhibited hardness values between 72 and 85 HV and an average ultimate tensile strength of 175 MPa. The observed mechanical scatter was consistent with localized microstructural heterogeneity and spatial defect distribution. The results demonstrate that geometric evaluation alone is insufficient as a quality metric for WAAM components and must be complemented by metallographic integrity assessment. Overall, the study highlights the importance of direct parameter optimization in double-wall WAAM structures to mitigate defect formation and enhance mechanical reliability under industrially accessible deposition conditions. Full article

This study assessed the carbonation-related durability of an existing reinforced concrete building in Seoul scheduled for demolition to examine the level of durability performance commonly assumed for building structures. The compressive strength of concrete core specimens was compared with the estimated compressive strength derived from the rebound hammer, showing similar overall trends despite noticeable scatter, indicating that rebound testing can serve as a supplementary indicator when interpreted with caution. Carbonation depth measurements revealed that indoor locations tended to exhibit the greatest carbonation depths, likely reflecting higher CO₂ concentrations associated with occupancy and daily activities, as well as indoor ventilation and moisture conditions. For exterior walls, orientation affected carbonation progress; carbonation depths were greater on the southwest-facing wall than on the northwest-facing wall, suggesting that higher solar radiation may promote drying and facilitate CO₂ diffusion, thereby accelerating carbonation. When the carbonation rate coefficients were compared under similar compressive strength conditions, the southeast-facing wall exhibited a coefficient approximately 1.1 times greater than that of the northwest-facing wall. These results indicate that carbonation cannot be explained by strength alone and highlight the importance of incorporating exposure-related factors (e.g., solar radiation, drying, rainfall, and shielding) into carbonation behavior assessment. Full article

High salinity and hardness in flowback fluids from tight reservoirs severely degrade the performance of conventional fracturing fluids, leading to formation damage and imposing major constraints on water recycling. An innovative in situ molecular interface regulation strategy that bypasses the need for costly pretreatment was proposed. A novel zwitterionic polymer was synthesized by grafting trimethylamine N-oxide (TMAO) onto hydrolyzed polyacrylamide. This hydrolyzed polyacrylamide grafted with trimethylamine N-oxide polymer (HPAMT) leverages zwitterionic TMAO groups to form a robust hydration layer approximately 0.25 nm thick on the polymer chains. Each TMAO group can immobilize up to 22.2 water molecules, effectively shielding the polymer from the detrimental effects of ions like Ca²⁺ and Na⁺, thereby preventing chain curling and preserving cross-linking sites. Experimental results demonstrate that HPAMT fracturing fluid prepared with untreated flowback fluids retains over 70% of its initial viscosity. The HPAMT fracturing fluid exhibits superior thermal and shear stability, maintaining more than 90% viscosity after exposure to 90 °C and the shear rate of 170 s⁻¹ for 60 min. Furthermore, HPAMT provides excellent proppant suspension, exceeding 60 min of static settling time. The broken gel viscosity remains below 5 mPa·s, enabling the direct reuse of flowback water. This technology overcomes the critical compatibility issue between traditional polymers and challenging brine chemistry, significantly reducing freshwater consumption and operational costs, thus presenting a viable and innovative solution for enhancing the environmental sustainability of unconventional resource development. Full article

Reasonable adjustment of construction parameters is of great value to reduce surface settlement and ensure the safety of shield construction. A novel hybrid intelligent optimization framework based on combination weighting and gray correlation analysis methods (CWG), a long short-term memory (LSTM) model and a chaotic particle swarm optimization with sigmoid-based acceleration coefficients (CPSOS) algorithm was proposed. The CWG method was employed to screen key construction parameters and determine the weights of various influencing factors of surface settlement, thereby constructing a CWG-LSTM prediction model for surface settlement. On this basis, the prediction model served as the objective function for optimizing construction parameters, and the CPSOS algorithm was used for the optimization of shield construction parameters. Based on the Qingdao Metro Line 4 in China, sample sets were collected to verify the performance of the developed framework. The CWG-LSTM model achieved coefficients of determination (R²) of 0.92 and 0.91 on the train and test sets, respectively, along with root mean square errors (RMSE) of 1.29 and 1.03, and mean absolute percentage errors (MAPE) of 15.60% and 17.18%. Its prediction ability surpasses that of other comparison models, such as the Gated Recurrent Unit, Random Forest, Transformer, and Multiple Linear Regression, demonstrating higher accuracy. Optimized construction parameters derived from the CWG-LSTM-CPSOS facilitated shield tunneling in the unconstructed section. All surface settlement monitoring results recorded during excavation fell within the safety threshold, demonstrating that the proposed hybrid intelligent optimization framework effectively manages surface settlement during shield tunneling and serves as a reliable optimization approach for construction parameters. Full article

The hanging net shielding system, employing a suspended cage-type enclosed structure to restrict the high-voltage transmission wire, has seen increasingly widespread application in transmission line crossing construction. However, the lack of a comprehensive dynamic analysis methodology has limited the standardization of its design and usage. In this investigation, a systematical dynamic modeling and analysis procedure of the hanging net shielding system is proposed based on the absolute nodal coordinate formulation (ANCF). The carrier cable, slings and transmission wire are discretized by the ANCF cable element. The spatial flexible beam–beam contact model and the assumption of a single contact area are adopted to perform the contact searching between the transmission wire and the horizontal pulley. The system dynamics analysis equation is assembled and solved by generalized alpha method. A full-scale model is simulated for the transmission wire impact condition and the variation history of the tension in carrier cable and the sling cable are given. The peak value of the tension in carrier cable could be 110 kN, while the largest tension in sling cable is 9 kN. Results could help to ensure construction safety, shorten the design cycle of the protection system and reduce the development cost at the same time. Full article

In-space manufacturing is essential for achieving long-term planetary colonization, particularly on Mars, where material transport from Earth is both costly and logistically restrictive. Traditional subtractive manufacturing methods are highly equipment-, energy-, and material-intensive, making additive manufacturing (AM) a more practical and sustainable alternative for extraterrestrial production. Among various AM technologies, laser beam powder bed fusion (PBF-LB) stands out due to its exceptional versatility, precision, and capability to produce dense metallic parts with complex geometries. However, conventional PBF-LB processes rely heavily on inert argon environments to prevent oxidation and ensure high-quality part formation—conditions that are difficult to reproduce on Mars. CO₂ makes up over 95% of the Martian atmosphere, meaning printing in a majority-CO₂ environment is of great interest for in situ manufacturing in a Martian colonization effort. This study investigates the feasibility of using pure carbon dioxide (CO₂) as a potential substitute for argon in PBF-LB manufacturing. Single-track and two-dimensional 316L stainless steel specimens were fabricated under argon, CO₂, and ambient air environments with a wide range of laser parameters to evaluate the influence of atmospheric composition on surface morphology, microstructural cohesion, and oxidation behavior. The results reveal that no single parameter controls the overall part quality; rather, a balance of parameters is essential to maintain thermal equilibrium during fabrication. Although parts produced in CO₂ exhibited slightly inferior surface finish, cohesion, and oxidation resistance compared to argon, they performed significantly better than those fabricated in ambient air in terms of balling effects and overall cohesion. These findings suggest that CO₂-assisted PBF-LB could enable sustainable in situ manufacturing on Mars and may also serve as a cost-effective alternative shielding gas for terrestrial applications. Full article

Shutdown dose rate (SDDR) assessments have been performed for the DEMO tokamak model, including the latest design and environmental configurations. The main objective of this study was to evaluate the shutdown radiation fields and establish dose rate limits to ensure safe personnel access to the Vacuum Vessel (VV) and nearby components. The simulations were based on the DEMO baseline model, further refined with the minor updates of the lower port, equatorial port limiter, and upper port assemblies. The computational approach employed the Monte Carlo particle transport code MCNP for neutron and photon transport calculations, coupled with the activation and decay code FISPACT-II to determine time-dependent decay gamma source terms. The mesh-coupled Rigorous Two-Step (R2Smesh) methodology developed in KIT was applied to achieve spatially resolved decay of photon source distributions and to compute corresponding SDDR 3D maps within the DEMO reactor configuration. The results provide a detailed characterization of the residual radiation environment inside the VV, offering insight into the accumulated activity, shielding performance of different materials, and potential access scenarios for maintenance operations in next-generation fusion devices. Full article

Conventional synchronous grouting materials often exhibit low early strength, delayed setting, and insufficient utilization of excavated soil, hindering the green and efficient advancement of metro shield tunneling technology. To overcome these challenges, this study developed a high-performance grouting material by utilizing shield muck—primarily composed of quartz (71.47%) and calcite (15.3%)—as the main raw material, with sodium trimethylsilanolate (TMS-Na) introduced as a performance enhancer. Through orthogonal experiments and range analysis, the influences of cement content, slag content, and TMS-Na dosage on the workability and mechanical properties of synchronous grouting materials were systematically evaluated. Microstructural evolution was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric (TG) analysis, and mercury intrusion porosimetry (MIP) to elucidate the mechanism by which TMS-Na modifies the grout microstructure. The results demonstrate that incorporating 8% slag and 0.2% TMS-Na increases the utilization rate of shield muck to 60.8%. Compared with conventional grouts, the novel material exhibits approximately 97.4% and 93.3% enhancements in 3-day and 28-day compressive strength, respectively, alongside an impermeability grade reaching P10. The addition of slag improves the apparent density and early strength of the grout, although its contribution diminishes at later ages. TMS-Na effectively activates the hydration reactivity of slag, accelerates early hydration, reduces the setting time, and participates in a secondary hydration reaction with argillaceous siltstone present in the excavated soil, promoting the formation of additional calcium silicate hydrate (C-S-H). This process densifies the hardened grout matrix, refines the pore structure, and significantly enhances both mechanical performance and impermeability. Field application in a trial tunnel section confirms that the proposed grouting material achieves complete cavity filling, eliminates water leakage, controls ground deformation effectively, and offers favorable economic viability, demonstrating strong potential for large-scale engineering application. Full article

Hydraulic supports, being the pivotal equipment in coal mining face operations, exhibit complex installation procedure knowledge that impedes efficient knowledge extraction and utilization, thereby hindering the provision of scientifically grounded installation guidance and ultimately affecting equipment installation efficiency. This study proposes the development of a domain-specific large-scale model utilizing named entity recognition (NER) for knowledge extraction to enhance the efficiency of hydraulic shield installation. Initially, a few-shot data augmentation method is introduced to enrich hydraulic shield assembly process data, thereby providing a robust dataset for fine-tuning the large language model (LLM). Subsequently, Low-Rank Adaptation (LoRA) fine-tuning techniques are leveraged to optimize large-scale model adaptation. Comparative analysis of the model’s performance post-fine-tuning was conducted using multiple evaluation metrics, revealing that the fine-tuned Deepseek-R1-7b-Distill model exhibited the most superior performance indicators. Ultimately, the fine-tuned Deepseek-R1-7b-Distill model was selected as the domain-specific LLM for NER in hydraulic support installation processes. The experimental results demonstrate that the entity recognition F1 score across all entity types reached 0.8887, validating the efficacy of the methodology. This provides technical support for enhancing the installation efficiency of hydraulic supports. Full article

Intentional high-power electromagnetic (EM) interference poses a serious threat to sensitive electronic systems and often manifests as ultra-wideband (UWB) sub- and nanosecond pulses. Metallic shielding enclosures with technological apertures are commonly used for protection; however, apertures enable electromagnetic coupling into the enclosure and limit shielding performance. While most existing studies focus on transient disturbances with durations exceeding the enclosure transit time, this work addresses an ultrashort high-power subnanosecond UWB plane-wave pulse whose duration is significantly shorter than the enclosure transit time, a regime that remains insufficiently explored. A time-domain numerical analysis is performed for a low-profile rectangular metallic enclosure with a front-wall aperture, focusing on internal EM field evolution, internal pulse formation, and polarization-dependent shielding effectiveness. Three-dimensional full-wave simulations were carried out using CST Microwave Studio over a 90 ns observation window. The results show that the incident pulse excites primary subnanosecond EM waves inside the enclosure, which subsequently generate secondary waves through multiple reflections from the enclosure walls. Their interaction produces complex, long-lasting, time-varying internal field patterns. Although attenuated, the resulting internal subnanosecond pulses repeatedly traverse the enclosure interior, forming a pulse train-like sequence that may pose a cumulative electromagnetic threat to internal electronics. A key contribution of this work is the quantification of time-dependent local shielding effectiveness for both electric and magnetic fields, derived directly from the internal pulse train-like series obtained in the time domain. The concept of local, time-dependent shielding effectiveness provides physical insight that cannot be obtained from a single globally averaged SE value. In the case of ultrashort electromagnetic pulse excitation, the internal field response of an enclosure is strongly non-stationary and highly non-uniform in space, with local field maxima occurring at specific times and locations despite good average shielding performance. Time-dependent local SE enables identification of worst-case temporal conditions, repeated high-amplitude internal exposures, and critical regions inside the enclosure where shielding is significantly weaker than suggested by global metrics. Therefore, while conventional SE remains useful as a summary measurand, local time-dependent SE is essential for assessing the actual electromagnetic risk to sensitive electronics under ultrashort pulse disturbances. In addition, a global shielding effectiveness metric mapped over selected enclosure cross-sections is introduced to enable rapid visual assessment of shielding performance. The analysis demonstrates a strong dependence of internal wave propagation, internal pulse formation, and both local and global shielding effectiveness on the polarization of the incident subnanosecond EM pulse. These findings provide new physical insight into aperture coupling and shielding behavior in the ultrashort-pulse regime and offer practical guidance for the assessment and design of compact shielding enclosures exposed to high-power UWB EM threats. Full article

Titanium-based alloys are widely used in dental implantology; however, the mechanical limitations of commercially pure titanium (cpTi) and unresolved concerns regarding stress shielding remain. This study evaluated the structure–property–function relationship of a novel β-type titanium-niobium-zirconium (Ti-Nb-Zr; TNZ) alloy for dental implant applications. Laboratory testing assessed the elemental composition, tensile properties, and fatigue resistance of the cpTi, compared with modified Grade 4 cpTi (MG4T). In parallel, a randomized, single-blind, controlled clinical trial was conducted over 12 months to compare the clinical performance of TNZ and MG4T implants under functional loading. A total of 80 participants (mean age: 54.2 years; 43 females, 37 males) were enrolled, with 77 completing the 12-month follow-up (TNZ: n = 38; MG4T: n = 39). Clinical outcomes included implant success and survival, peri-implant soft tissue parameters, marginal bone levels, fractal dimension (FD) analysis of trabecular bone, and adverse events. TNZ implants demonstrated superior fatigue resistance without an increase in the elastic modulus relative to MG4T. Clinically, both groups achieved 100% implant success and survival, with no implant-related adverse events. FD analysis revealed time-dependent bone remodeling without evidence of pathological adaptation. These findings support the functional viability of TNZ as a mechanically robust, biocompatible implant material. Further long-term, multicenter trials are warranted to confirm sustained clinical benefits and broader applicability. Full article

Background: Artesunate (ART), a natural product derivative of artemisinin, exhibits striking antitumor activity. However, the clinical translation of ART is limited by rapid clearance, poor tumor selectivity, and severe off-target toxicity. To address these limitations, we developed an unsaturated aliphatic chain-driven nanoassembly strategy to optimize the therapeutic performance of ART. Methods: We designed and synthesized two ART derivatives by conjugating saturated aliphatic chains (ART-SAs) or unsaturated aliphatic chains (ART-LAs) to ART, which subsequently self-assembled into carrier-free nanoassemblies (NAs). These NAs were characterized for their self-assembly capacity and colloidal stability. Biological evaluations included studies on cellular uptake efficiency, in vivo pharmacokinetics, and antitumor efficacy in a tumor-bearing mouse model. Results: The saturated aliphatic chain is found to drive nanoassembly of ART-SA but significantly shields the antitumor activity of ART. Interestingly, the conjugate of an unsaturated aliphatic chain to ART (ART-LA) not only shows outstanding self-assembly capacities but also retains the native antitumor activity of ART. The P-AL NAs with improved pharmacokinetics and tumor-specific biodistribution exert potent antitumor activity and favorable safety. Conclusions: We successfully applied ART for highly effective antitumor therapy by employing an unsaturated aliphatic chain-driven strategy. This study is conducive to promoting the clinical application of ART. Full article

Efficient on-site connection of power cable conductors is critical for ensuring the safe operation of the power grid. Traditional thermite welding methods pose significant safety risks, including open flames and fumes. Meanwhile, induction heating, when applied to cable conductors, faces challenges of severe magnetic field dispersion, low heating efficiency, and a high risk of damaging adjacent insulation layers. This paper proposes a novel magnetic flux control system based on gradient permeability ceramics to address these issues. The core of this system is the synergistic utilization of a gradient permeability composite ceramic mold and a high-permeability shielding shell. A 2D axisymmetric multiphysics coupled model was established to compare the performance of the optimized system with a conventional case and single control components. Simulation results demonstrate that the optimized system increases the magnetic flux density at the weld seam to 3.7 times that of the conventional setup (0.263 T). Consequently, the weld seam of the 240 mm² copper conductor is rapidly heated to the melting point of copper (1083 °C) within 7.78 s. Due to the high heating rate, upon completion of the welding process, the temperatures of the inner shielding and insulation layers are only 48.8 °C and 24.3 °C, respectively, well below the materials’ safety thresholds. These findings suggest that the proposed magnetic flux control strategy achieves rapid and precise heating, offering a theoretical foundation for the development of high-performance on-site equipment for fabricating cable joints. Full article

Background/Objectives: Dental implants are a preferred solution for missing teeth, but peri-implantitis remains a major challenge in implant dentistry. This narrative review provides an overview of the therapeutic interventions for peri-implantitis based on the current literature and illustrates a new clinical approach using novel magnesium membrane through three case presentations. Methods: A comprehensive literature search on peri-implantitis management was conducted, with emphasis on current clinical practice guidelines. In addition, three clinical cases were presented to demonstrate the use of a fully resorbable magnesium membrane in combination with a bovine xenograft with hyaluronate. Results: The narrative review identified and summarized a wide range of non-surgical and surgical therapeutic strategies for treatment of peri-implantitis. Additionally, three case reports with novel magnesium membrane highlighted distinct clinical scenarios: (1) bone defect reconstruction without implant removal, (2) reconstruction following implant removal, and (3) a minimally invasive shield technique performed without removal of the implant or crown. All cases demonstrated favorable clinical outcomes following the novel biomaterial approach. Conclusions: The combination of a resorbable magnesium membrane with bovine xenograft with hyaluronate represents a promising therapeutic strategy for treatment of peri-implantitis. This approach may improve clinical outcomes and potentially set new standards in implant dentistry. Further studies with larger cohorts and control groups are required to confirm these preliminary findings. Full article