Search Results (150)

With the rapid evolution of 5G wireless communications, millimeter-wave (mmWave) technology has become a crucial enabler for high-speed, low-latency, and large-scale connectivity. As the critical interface for signal transmission, mmWave antennas directly affect system performance, reliability, and application scope. This paper reviews the current state of mmWave antenna technologies in 5G systems, focusing on antenna types, design considerations, and integration strategies. We discuss how the multiple-input multiple-output (MIMO) architectures and advanced beamforming techniques enhance system capacity and link robustness. State-of-the-art integration methods, such as antenna-in-package (AiP) and chip-level integration, are examined for their importance in achieving compact and high-performance mmWave systems. Material selection and fabrication technologies—including low-loss substrates like polytetrafluoroethylene (PTFE), hydrocarbon-based materials, liquid crystal polymer (LCP), and microwave dielectric ceramics, as well as emerging processes such as low-temperature co-fired ceramics (LTCC), 3D printing, and micro-electro-mechanical systems (MEMS)—are also analyzed. Key challenges include propagation path limitations, power consumption and thermal management in highly integrated systems, cost–performance trade-offs for mass production, and interoperability standardization across vendors. Finally, we outline future research directions, including intelligent beam management, reconfigurable antennas, AI-driven designs, and hybrid mmWave–sub-6 GHz systems, highlighting the vital role of mmWave antennas in shaping next-generation wireless networks. Full article

In order to enhance the heat dissipation of a chip, this work investigates the enhancement of the thermal homogenization effect of a ceramic substrate with a high-thermal-conductivity graphene material to improve the interfacial heat transfer performance. AgCuTi-activated brazing material is used to connect the graphene film/AlN. The mechanism of the influence of brazing temperatures on the microstructure and thermal conductivity of joints is discussed. The thermal conductivity of the graphene/AlN double layer composite brazed at 890 °C for 10 min holding time was the highest at 482.3 W m⁻¹ K⁻¹. This study provides a new solution for the application of AlN ceramics in high-heat-flow scenarios. Full article

Background/Objectives: Anterior dental trauma in adolescents presents complex restorative challenges due to ongoing craniofacial development and high aesthetic expectations. This study evaluated the long-term clinical performance of feldspathic ceramic veneers and lithium disilicate crowns used in the anterior region following dental trauma in adolescents. Methods: A total of 209 restorations were placed in 85 adolescents (50 females, 35 males), aged 11.1–17.9 years (mean age: 15.1 years). Of these, 144 were lithium disilicate crowns, and 65 were feldspathic ceramic veneers. All restorations were fabricated using minimally invasive protocols and followed up for periods ranging from 3 to 60 months. Outcomes were assessed based on standardized clinical criteria for success and failure. Results: Lithium disilicate crowns exhibited superior long-term performance, with the majority of failures occurring in feldspathic veneers (p < 0.001), primarily due to chipping or structural fracture. Age and gender had no statistically significant influence on failure rates. Conclusions: Both feldspathic and lithium disilicate ceramic restorations represent viable treatment options for anterior dental trauma in adolescents. However, lithium disilicate demonstrates greater mechanical reliability, particularly in teeth with significant hard tissue loss. These results support the use of durable ceramic materials in adolescent restorative protocols involving dental trauma. Full article

Stainless steel is recognized for its excellent durability and anti-corrosion properties, which are essential qualities across various industrial applications. The machining of stainless steel, particularly under a dry environment to attain sustainability, poses several challenges. The poor heat conductivity and high ductility of stainless steel results in poor heat distribution, accelerating tool wear and problematic chip formation. To mitigate these challenges, the implementation of surface texturing has been identified as a beneficial strategy. This study investigates the impact of wave-type texturing patterns, developed on the flank surface of tungsten carbide ceramic tool inserts, on the machinability of AISI 316 stainless steel under dry cutting conditions. In this investigation, chip morphology and surface roughness were used as key indicators of machinability. Analysis of Variance (ANOVA) was conducted for chip thickness, chip thickness ratio, and surface roughness, while Taguchi mono-objective optimization was applied to chip thickness. The ANOVA results showed that linear models accounted for 71.92%, 83.13%, and 82.86% of the variability in chip thickness, chip thickness ratio, and surface roughness, respectively, indicating a strong fit to the experimental data. Microscopic analysis confirmed a substantial reduction in chip thickness, with a minimum observed value of 457.64 µm. The corresponding average surface roughness Ra value 1.645 µm represented the best finish across all experimental runs, highlighting the relationship between thinner chips and enhanced surface quality. In conclusion, wave textures on the cutting tool’s flank face have the potential to facilitate the dry machining of AISI 316 stainless steel to obtain favorable machinability. Full article

Background/Objectives: Full-arch implant-supported prostheses have become a widely accepted solution for edentulous patients, yet long-term biological and mechanical complications remain a clinical concern. Methods: This retrospective study included 70 fully edentulous patients (362 implants) rehabilitated with either fixed or removable implant-supported prostheses. Data were collected on demographics, medical status, type and location of prostheses, implant type, abutments, method of fixation, and complications. Statistical analysis included Fisher’s exact test, the Mann–Whitney U test, and chi-squared tests, with a significance level set at p < 0.05. Results: Mechanical complications occurred in 41.4% of patients (29 out of 70), with framework fractures reported in eight cases (27.6%), ceramic chipping in six cases (20.7%), and resin discoloration in four cases (13.8%). The prostheses were fabricated using monolithic zirconia, metal–ceramic crowns, zirconia on titanium bars, and hybrid resin/PMMA on cobalt–chromium frameworks. Gingival inflammation was also noted in 41.4% of cases (n = 29), predominantly in posterior implant regions. Younger patients and those without systemic diseases showed a significantly higher incidence of mechanical complications. Conclusions: Two years post-treatment, mechanical and biological complications appear to be independent phenomena, not significantly associated with most prosthetic variables. Patient-specific factors, particularly age and general health status, may have greater predictive value than prosthetic design. Limitations of the study include its retrospective design and the lack of radiographic data to assess peri-implant bone changes. Full article

Recycled materials have gained extensive recognition in many industrial sectors for enhancing sustainability and reducing environmental impacts. Combining ceramic tile waste (CTW) in concrete mixes with recycled aggregate will help lower natural aggregate demand and reduce the amount sent to landfill. This paper aims to study the mechanical properties of CTW in concrete mixes as a brick aggregate replacement and its impact on concrete strength and durability. To evaluate and assess their strength and durability, three types of concrete cubes were prepared using 20%, 40%, and 70% of waste ceramic tiles as a replacement for coarse aggregate. Two kinds of concrete samples were also prepared with conventional coarse aggregate as the control specimen (CC). A 1:2:4 concrete mixed ratio was used in this research with a 0.50 water–cement ratio. The samples were tested after 14 days and 28 days to assess their mechanical properties, including strength and durability. When CTW was added to concrete mixtures instead of brick chips, the mechanical strength rose considerably, and the water absorption performance increased. Moreover, replacing brick chips with ceramic waste in concrete could have significant environmental benefits. Full article

This study aimed to evaluate prosthetic complications, implant survival rates, and marginal bone loss in implant-supported monolithic restorations compared to metal-ceramic restorations. The study was registered in PROSPERO (CRD420251022336) and conducted following the Cochrane Handbook for Systematic Reviews of Interventions and PRISMA guidelines. A systematic search was conducted in the electronic databases MEDLINE/PubMed, Web of Science, Scopus, Embase, and ProQuest for articles published up to December 2024. The inclusion criteria comprised studies evaluating only randomized clinical trials that evaluated implant-supported monolithic restorations directly compared to metal-ceramic restorations, considering any type of ceramic material and regardless of the fixation system (screw-retained or cemented), with a minimum follow-up of one year. A meta-analysis was performed using RevMan 5.4 software, and the risk of bias and certainty of evidence were assessed using the RoB 2.0 and GRADE tools, respectively. A total of six studies were included, all of which exclusively evaluated monolithic zirconia single crowns over follow-up periods ranging from 1 to 3 years. None of the included studies evaluated fixed partial dentures or restorative materials other than monolithic zirconia. In total, 267 patients (mean age range: 18–57 years) were analyzed, with a total of 174 implant-supported monolithic zirconia crowns and 165 metal-ceramic single crowns in the posterior region (premolars and molars). The meta-analysis revealed that implant-supported monolithic zirconia single crowns exhibited significantly fewer prosthetic complications compared to metal-ceramic single crowns (p < 0.0001; Risk Ratio [RR]: 0.26; Confidence Interval [CI]: 0.14–0.47). However, no statistically significant differences were observed between implant-supported monolithic zirconia and metal-ceramic single crowns regarding implant survival rates (p = 0.36; RR: 1.66; CI: 0.56–4.94) or marginal bone loss (p = 0.15; Mean Difference [MD]: −0.05; CI: −0.11–0.02). The risk of bias assessment indicated that four studies had a low risk of bias. However, the certainty of evidence was classified as low for prosthetic complications and implant survival rates and very low for marginal bone loss. Within the limitations of this review, it can be concluded that implant-supported monolithic zirconia single crowns can be considered a favorable treatment option as they show comparable implant survival and bone stability to metal-ceramic crowns, with a potential reduction in short-term prosthetic complications such as screw loosening and ceramic chipping. However, due to the limited number of studies included and low certainty of evidence, further long-term research is still needed to confirm their clinical performance over time. Full article

Artificial retinal devices require a high-density electrode array and mechanical flexibility to effectively stimulate retinal cells. However, designing such devices presents significant challenges, including the need to conform to the curvature of the eyeball and cover a large area using a single platform. To address these issues, we developed a parylene-based multi-module retinal device (MMRD) integrating a complementary metal-oxide semiconductor (CMOS) system. The proposed device is designed for suprachoroidal transretinal stimulation, with each module comprising a parylene-C thin-film substrate, a CMOS chip, and a ceramic substrate housing seven platinum electrodes. The smart CMOS system significantly reduces wiring complexity, enhancing the device’s practicality. To improve fabrication reliability, we optimized the encapsulation process, introduced multiple silane coupling modifications, and utilized polyvinyl alcohol (PVA) for easier detachment in flip-chip bonding. This study demonstrates the fabrication and evaluation of the MMRD through in vitro and in vivo experiments. The device successfully generated the expected current stimulation waveforms in both settings, highlighting its potential as a promising candidate for future artificial vision applications. Full article

Effective thermal management of electronic modules is crucial to the reliable operation of variable frequency air conditioners. For this reason, two types of plate-finned heat sinks of electronic modules were selected. The experiments utilized ceramic heating plates to simulate chip heating, conducted in an enthalpy difference laboratory with controlled environments. Four installation cases were analyzed to evaluate the impact of heat sink orientation, airflow direction, and structural layout. The results showed that when multiple chips were arranged on the same heat dissipation substrate, the heat dissipation process of the chips would be coupled with each other, and the rational layout of the chips played an important role in heat dissipation. In the case of cooling air impacting the jet, the heat dissipation performance of the heat sink was significantly improved, and the heat transfer coefficient of the heat sink was as high as 316.5 W·m⁻²·°C⁻¹, representing a 6.9% improvement over conventional designs (case I: 296.1 W·m⁻²·°C⁻¹). The maximum temperature of the chips could be reduced by 11.1%, which is 10.1 °C lower. This study will provide a reference for the optimization design of the heat sink of the electric control module in inverter air conditioners. Full article

This paper presents research findings on the turning of AZ31B magnesium alloy using ceramic-coated tungsten carbide tool inserts in a dry environment. Fifteen experiments were conducted according to the Box–Behnken design (BBD) for the straight turning of AZ31B magnesium alloy to investigate the variations in two important machinability indicators, i.e., material removal rate ‘MRR’ and mean roughness depth ‘R_Z’, with variations in cutting speed ‘C_S’, feed rate ‘f_r’, and depth of cut ‘DoC’. The cutting speed and feed rate had the maximum influence on the mean roughness depth and material removal rate, respectively. To address the challenge of optimizing conflicting machining responses, desirability function analysis (DFA) and grey relational analysis (GRA) were employed to identify the optimal turning parameters for conflicting machinability indicators or responses. These techniques enabled the simultaneous maximization of the material removal rate and the minimization of the mean roughness depth, ensuring an effective balance between productivity and surface quality. The optimal turning conditions—cutting speed of 90 m/min, feed rate of 0.2 mm/rev, and depth of cut of 1.0 mm—yielded the best multiperformance results with an MRR of 18,000 mm³/min and an R_Z of 2.21 µm. Scanning electron microscope (SEM) analysis of the chip and flank surface of the cutting tool insert used in the confirmation tests revealed the formation of band-saw-type continuous chips and tool wear caused by adhesion and abrasion. Full article

This paper aims to investigate the effectiveness of cutting fluid during the high-speed face-turning of superalloy Inconel 718 using chamfered whisker-reinforced ceramic inserts. It addresses this topic by providing a comprehensive understanding of the machinability of Inconel 718 under both dry and wet conditions through analytical friction modeling and a detailed analysis of the chip formation process. Two new indexes, named the Area Function (AF) and the Shape Function (SF), were derived to assess the serration intensity of the chips. Particular attention was paid to the interaction between the cutting speed and the cutting fluid. The results showed that wet conditions promote uniform chip formation, more stable forces, a lower coefficient of friction, and the absence of notch wear. At low cutting speed (60 m/min) and dry machining results in high serration intensity (SF = 0.7) and segmentation frequency ($f_{seg}$ = 22.08 kHz) compared to the SF of 0.4 and $f_{seg}$ = 19.69 kHz in wet conditions. The segmentation frequency increases significantly with cutting speed, reaching 71.03 kHz and 63.32 kHz at a cutting speed of 225 m/min for dry and wet conditions, respectively. It was also found that the rate of increase in the tangential force was lower (20.49 N/s) when using cutting fluid at a high cutting speed (225 m/min) compared to dry conditions (27.37 N/s). Full article

The impact of ice and snow in seasonally frozen regions has led to a significant decline in the flatness and skid resistance of highway pavements, creating severe traffic safety hazards. With economic development driving the transition from road construction to maintenance, this study proposes enhancing Ultra-Thin Wearing Course (UTWC) maintenance materials with anti-icing performance and snow-melting properties. The study first employed the Marshall mix design method to develop gradations for two common types of UTWC asphalt mixtures: the dense-graded GT-8 and the open-graded NovaChip^® Type-B. Using the volume substitution method, aggregates were replaced with equivalent volumes of ceramic grains. The optimal asphalt–aggregate ratios for the mixtures with varying ceramic grain contents were determined, and the influence of ceramic grains content on the asphalt–aggregate ratio was analyzed. The results indicate that the optimal asphalt–aggregate ratio increases with higher ceramic grains content. Subsequently, the high-temperature performance, low-temperature performance, and water stability of UTWC with varying ceramic grain contents were evaluated. Overall, NovaChip^® gradation mixtures demonstrated superior road performance compared to GT-8 gradation mixtures. Moreover, an increase in ceramic grains content enhanced the high-temperature performance of UTWC but moderately reduced its low-temperature performance and water stability. Finally, the effects of different ceramic grain contents and snowmelt agent types on the anti-icing and snowmelt properties of UTWC were examined. The results revealed that higher ceramic grains content improved snowmelt effectiveness. Considering the road performance of the specimens, a ceramic grains content of 40% was recommended. Furthermore, calcium chloride (CaCl₂) exhibited superior anti-icing performance compared to other snowmelt agents. Full article

In this article, hot-pressed PZT ceramics were used as a sensitive element material and made into a pyroelectric chip. Three current mode sensors were fabricated using a pyroelectric chip of different thicknesses (80 μm, 40 μm, and 30 μm). The voltage responsivity of sensors reached the order of magnitude of 10⁵. The size effect resulting from varying the thickness was studied. The results indicate that as the thickness decreases, the performance significantly increases. When the modulation frequency is 10 Hz, the specific detectivity of the sensor with a 30 μm PZT ceramic pyroelectric chip reaches 5.3 × 10⁸ cm·Hz^1/2/W. Full article

Background and Objectives: This five-year retrospective study evaluated the survival and clinical performance of 1143 zirconium oxide restorations, including both monolithic (144) and layered (999) restorations. Materials and Methods: The analysis included clinical records and follow-up data of patients treated with zirconium oxide restorations. Failures in layered restorations were examined, particularly focusing on chipping caused by unsupported feldspathic ceramic exceeding 1.5 mm. Monolithic restorations were used as a benchmark for durability. Results: The results demonstrated a high overall survival rate of 96.3%, with monolithic restorations achieving a perfect survival rate of 100%, while layered restorations had a survival rate of 95.8%. Failures in the layered restorations were primarily associated with chipping, especially when the unsupported feldspathic ceramic exceeded 1.5 mm. Conclusions: This finding highlights the importance of maintaining adequate support for the ceramic layer to prevent such complications. Monolithic restorations, in contrast, showed superior durability, with no failures reported, making them a more reliable option for long-term success. These findings emphasize the need for the careful selection of zirconium oxide restoration types based on the clinical context, particularly in cases where durability is critical. Full article

Sandblasting and acid etching are common procedures used to treat implant surfaces, enhancing osseointegration and improving clinical success rates. This clinical study aimed to evaluate the long-term outcomes of sandblasted and acid-etched implants. A total of 303 implants were placed in 114 partially and totally edentulous patients using a two-stage surgical technique and an early loading protocol (6–8 weeks). Clinical findings for implants and prosthetics were evaluated over a 12-year follow-up period. A total of 12 implants (3.9%) failed, with 3 failures occurring during the healing period before loading and 9 due to peri-implantitis. The cumulative survival rate for all implants was 96.1%. A total of 156 prostheses were placed on 300 implants, 87 single crowns, 45 partial fixed bridges, 9 full-arch fixed restorations, and 15 overdentures. The mean marginal bone loss was 1.18 mm. (SD. 0.64 mm.). Thirty-nine implants (13%) in twenty-four patients exhibited peri-implantitis. Technical complications, including prosthetic screw loosening or fracture, ceramic chipping, and acrylic fractures, were observed in 24 subjects (21.1%). Sandblasted and acid-etched surface implants placed in the maxilla and mandible reported favorable outcomes and stable tissue conditions with an early loading protocol. Full article