Search Results (110)

This study explores the miniaturization of the Controlled Reception Pattern Antenna (CRPA) for Global Positioning System (GPS) receivers, addressing the challenge of mutual coupling, which adversely affects antenna performance. In this work, a miniaturized CRPA is designed and manufactured by using Rogers RO3006 substrate. To provide a performance benchmark, a four-element reference CRPA array was also designed with a 0.5 λ inter-element spacing, yielding an overall aperture size of 149.58 mm × 150.24 mm and a worst-case inter-element isolation larger than 14.4 dB. For the miniaturized CRPA, the target inter-element spacing was set to be 0.3 λ. To overcome isolation limitations, several coupling-mitigation techniques were developed and integrated into the miniaturized design. The final configuration consisted of a four-element CRPA, with each element rotated by 90° relative to its neighbor, inter-element slots incorporated into the shared ground-plane, and an individual ground plane segmentation to reduce surface–wave coupling. The proposed miniaturized CRPA achieved an overall footprint of 104.21 mm × 104.55 mm with the worst-case isolation exceeding 18.36 dB, surpassing the isolation performance of the reference array. This work demonstrates that it is possible to realize a compact CRPA with enhanced inter-element isolation by integrating tailored coupling suppression methods. Full article

In terrestrial environments, nest site selection by birds and mammals is often related to the physical attributes of surrounding vegetation. Similarly, some elasmobranchs use different habitats, including kelps, as oviposition sites. However, habitat features that drive oviposition site selection remain poorly understood. We examined the relationship between kelp morphology (holdfast diameter, number of stripes, and total length) and kelp forest configuration (density, size structure, predator density) with egg presence to identify the factors influencing oviposition choice in the redspotted catshark (Schroederichthys chilensis). We conducted surveys over a latitudinal gradient (19° S to 39° S), encompassing much of the overlap between the kelp, Lessonia trabeculata and S. chilensis in Chile. Eggs were exclusively attached between the upper stipe and basal fronds of Lessonia trabeculata in all sites. At the individual scale, S. chilensis selected larger kelps within a patch, independent of the general population size structure. The number of eggs and clutches was positively associated with stipe length and holdfast diameter. Across all sites, egg-bearing kelps were consistently clustered at a similar depth in the kelp forest rather than being randomly distributed. At the site scale, egg number had a negative correlation with their main predator abundance, Taliepus dentatus, and juvenile kelp density. These results suggest that S. chilensis shows low plasticity in substrate use, as evidenced by non-random, consistent oviposition in kelp morphology along a latitudinal gradient. Our results underscore the need to incorporate kelp size thresholds and the protection of egg-bearing aggregations into harvesting regulations, as overexploitation of L. trabeculata directly threatens the reproductive viability of S. chilensis. Full article

This study investigates how processing parameters and powder characteristics influence the mechanical performance of thermal barrier coatings (TBCs) applied to a Ti-6Al-4V alloy. Two TBCs were deposited by Atmospheric Plasma Spray (APS) using different processing conditions, feedstock characteristics, and coating thicknesses (thin and thick configurations). TBC characterization included powder size analysis, scanning electron microscopy (SEM), surface roughness, X-ray diffraction, instrumented indentation, and scratch testing. Mechanical behavior was assessed using creep testing at 125 MPa and 500 °C for coated and uncoated samples. Fracture surfaces of crept samples were analyzed by SEM and stereomicroscopy. Thicker TBC exhibited higher elastic modulus but contained microcracks and higher porosity, resulting in a higher steady-state creep rate (0.0006 h⁻¹, approximately 167% above the uncoated substrate) and reduced rupture time. Conversely, thinner TBC remained initially crack-free, promoting stress redistribution and leading to a lower creep rate (0.0002 h⁻¹, about 67% below the substrate) and delayed failure. Fractographic analysis revealed ductile fracture of Ti-6Al-4V in all conditions, indicating that coatings influenced damage accumulation rather than fracture mode. These findings underscore the combined effect of processing parameters and coating architecture on TBC performance for aerospace applications. Full article

This paper presents the design of a compact four-element MIMO antenna based on a metamaterial structure and a reactive load generated by an open-circuit stub. The radiator array, arranged in an axial symmetry configuration, provides high inter-element isolation despite a sub-millimeter separation. The design is optimized for 5G n77/n78 band applications and employs a metamaterial structure composed of embedded octagonal split-ring resonators (SRRs) integrated on a Duroid RT5880 0500 (${ϵ}_r=2.2,h=1.27 \mathrm{m}\mathrm{m}$) substrate. This configuration achieves high miniaturization, with individual radiators of $19\times 9.53 \mathrm{m}{\mathrm{m}}^2$. Furthermore, through a stub-loading technique, the array is enhanced in two significant aspects: (a) it exhibits an increased impedance bandwidth, rising from a 23% fractional bandwidth in the stub-less design to 39% in the final architecture; and (b) a shift of the lower cut-off frequency toward lower values is obtained, resulting in a reduction of the radiator’s electrical length, which translates into physical size diminution. The total array has a size of only $28.8\times 28.8 \mathrm{m}{\mathrm{m}}^2$ ($0.24{\lambda }_0\times 0.24{\lambda }_0$, considering the lower cut-off frequency). Despite the proximity between radiators and the absence of electromagnetic decoupling structures, the design ensures inter-element isolation exceeding 15 dB in the lower band and reaching values above 20 dB in the mid and upper bands. Diversity metric analysis confirms high performance, yielding an Envelope Correlation Coefficient (ECC) $\ll 0.005$, Diversity Gain (DG) close to the ideal value ($\ge 9.9$), Total Active Reflection Coefficient (TARC) below −10 dB (converging in random phase analysis), and a Channel Capacity Loss (CCL) of less than $0.4$ bits/s/Hz. Therefore, the proposed antenna stands as an ideal design for compact 5G communication devices. Full article

This study introduces two compact wideband substrate-integrated waveguide (SIW) filters fabricated using thin-film technology. The wideband bandpass response is achieved by incorporating interdigital capacitor (IDC) structures into a half-mode SIW (HMSIW) transmission line. An equivalent LC circuit model is formulated to analyze the influence of IDC parameters on the generation of transmission zeros. For the first filter (BPF 1), a third-order IDC coupling configuration is employed, resulting in a 1 dB passband spanning 11 GHz to 18 GHz, a minimum insertion loss of 0.66 dB, three transmission zeros that enhance stopband performance, and a compact core dimension of $0.49{\lambda }_g\times 0.29{\lambda }_g$. For further miniaturization, a modified HMSIW transmission line incorporating a metal-insulator-metal (MIM) capacitor at the equivalent magnetic wall is proposed. This design effectively reduces the transverse dimension of the waveguide while maintaining the original cutoff frequency. Utilizing this configuration, the second bandpass filter (BPF 2) was designed and fabricated employing double-layer ceramic thin-film technology. The resulting filter exhibits a 1 dB passband spanning 10 GHz to 18 GHz, a compact footprint measuring $0.44{\lambda }_g\times 0.23{\lambda }_g$, a minimum insertion loss of 0.58 dB, and features three transmission zeros. The fabricated and measured results of both filters show good agreement with simulations. Compared with previously reported wideband SIW filters, the proposed designs demonstrate comprehensive advantages in fractional bandwidth, insertion loss, out-of-band suppression, and circuit size, providing effective filtering solutions for high-density integration of microwave and millimeter-wave RF systems. Full article

This article introduces a novel right-angle coax to Substrate Integrated Coaxial (SIC) transition, offering featured characteristics and performance in a compact size. An air-filled K-connector is used to ensure optimal transition in a compact form factor. The proposed transition covers the Ku-band up to 18 GHz, achieving a deep matching level below 20 dB. The transition is fabricated and tested in a back-to-back configuration, where it demonstrates impressive characteristics, including a matching level of −15 dB and an insertion loss of −0.22 dB/inch across the entire bandwidth for the back-to-back configuration. Full article

This work presents the design of a compact, wideband circular microstrip patch antenna for microwave imaging-based brain tumor detection. The main contribution is the development of a compact antenna structure incorporating enhanced ground-plane slot modifications, which significantly improves impedance bandwidth while maintaining a small electrical size, making it highly suitable for medical imaging systems. In addition, the study integrates antenna design, safety evaluation, and microwave imaging analysis within a unified framework to assess tumor localization feasibility using a realistic head model in CST Microwave Studio. The proposed antenna is fabricated on an FR-4 substrate with dimensions of 37 × 54.5 × 1.6 mm³, corresponding to an electrical size of 0.176λ × 0.260λ × 0.0076λ at the lowest operating frequency of 1.43 GHz. Ground-plane slot enhancements are introduced to achieve wideband performance, resulting in an impedance bandwidth from 1.43 to 4 GHz and a fractional bandwidth of 94.7%. The antenna exhibits a maximum realized gain of 3.7 dB. To evaluate its suitability for medical applications, specific absorption rate (SAR) analysis is performed using a realistic human head model at multiple antenna positions and at 1.5, 2.1, 2.5, 3.3, and 3.9 GHz frequencies. The computed SAR values range from 0.109 to 1.56 W/kg averaged over 10 g of tissue, satisfying the IEEE C95.1 safety guideline limit of 2 W/kg. For tumor detection assessment, time-domain simulations are conducted in CST Microwave Studio using a monostatic radar configuration, where the antenna operates as both transmitter and receiver at twelve angular positions around the head with 30° increments. The collected scattered signals are processed using the Delay-and-Sum (DAS) beamforming algorithm to reconstruct dielectric contrast maps and localize the tumor. It should be noted that the tumor-imaging demonstrations presented in this work are based on numerical simulations, while experimental validation is limited to the characterization of the fabricated antenna. Nevertheless, the findings indicate that the proposed antenna is a promising candidate for noninvasive, low-cost microwave brain tumor imaging applications. Full article

This paper presents a compact multi-beam dual-circularly polarized phased array receiving system operating in the 10.7–12.7 GHz frequency band is designed and implemented, which can generate eight reconfigurable receiving beams with independently configurable polarization modes and scanning directions for each beam. To improve the aperture utilization efficiency of the array and reduce the array size, the proposed phased array architecture adopts a “full-aperture multiplexing” beamforming method, where all beams share the same array aperture. For cost-effective phased array architecture with two-dimensional scalability, the array is divided into several identical receiving subarrays, with the control and power supply modules arranged beneath the array aperture. In addition, a heterogeneous integration scheme is introduced to realize high-density integration of various receiving functional chips, which reduces the overall array footprint by approximately 30% while maintaining the basic performance of the system gain-to-noise-temperature ratio (G/T). Meanwhile, different dielectric substrates are adopted to implement multi-level combining networks, optimizing the trade-off between overall efficiency and cost. To verify the feasibility of the proposed architecture, a prototype with a 16 × 16 array configuration is developed and tested. The measured results show that the array gain reduction is no more than 4 dB at a maximum scanning angle of 60°, and the G/T value of all beams in the boresight direction is not less than 0.9 dB/K at 11.7 GHz. The experimental results validate the effectiveness of the proposed multi-beam dual-circularly polarized phased array architecture in terms of engineering implementation and system performance. Full article

Laser beam powder bed fusion (PBF-LB) enables the fabrication of complex rotational metallic components for aerospace applications, such as engine exhaust nozzles and combustion liners, but the localized thermal cycles inherent to the process often lead to residual stress accumulation and geometry-dependent distortion, particularly in low-stiffness and open structures. This study investigates the thermo-mechanical response of three representative 316L stainless steel rotational geometries—dumbbell-shaped, cylindrical, and drum-shaped—in both closed and open configurations using a transient, fully coupled thermo-mechanical finite element model validated by high-resolution three-dimensional deformation measurements. The results reveal pronounced geometry- and size-dependent distortion mechanisms: for closed structures, the drum-shaped geometry exhibits the largest radial contraction and stress concentration due to its larger characteristic size and lower stiffness, with a maximum deformation of approximately 0.14 mm, whereas the dumbbell-shaped and cylindrical geometries show smaller and more uniform deformations of about 0.09 mm and 0.12 mm; open configurations experience substantially amplified distortion, with both the magnitude and vertical location of bulging governed by geometric stiffness and substrate constraint, and the open drum-shaped structure reaching a maximum displacement of approximately 1.6 mm. These findings clarify how geometric size and stiffness control stress relaxation and shape stability in PBF-LB-fabricated rotational components and provide transferable guidance for geometry-informed design and distortion mitigation in high-precision additive manufacturing. Full article

Two approaches are described for construction of a screen-printed planar electrode (SPE) for potentiometric determination of iodide ion. The first, involves preparation and application of iron(II) bathophenanthroline tetraiodoplumbate complex ([Fe(bphen)₃][PbI₄]), as a sensitive and selective electroactive sensing material in a potentiometric electrode for iodide determination. The second is the use of a nano-sized poly(aniline-co-thiophene) (PANI-co-PT) as a solid-contact material in a planar miniaturized configuration. The SPE displays a Nernstian response for iodide ion with a calibration slope of −58.81 ± 0.69 mV/decade (R² = 0.9998) over a wide concentration range (9.17 × 10⁻⁷–6.94 × 10⁻³ mol/L), low detection limit (6.09 × 10⁻⁷ mol/L), rapid response time (5.0 ± 1.0 s) and long-life span (75 ± 3.0 d). The use of PANI-co-PT solid-contact layer significantly improves the ion-to-electron transduction, eliminates the formation of undesired thin water layer between the sensing membrane and the conducting substrate, prevents membrane delamination, enhances potential stability with a significantly reduced potential drift (8.32 ± 0.12 µV/min) and displays high redox capacitance (2.560 ± 0.040 mF). Water contact angle measurements confirm the increased hydrophobicity of the modified membrane electrode (from 44 ± 0.8° to 93 ± 1.4°) and demonstrate the membrane ability to repel moisture and further stabilize the sensor response. The proposed sensor is successfully integrated into a flow injection analysis (FIA) system to enable real-time and continuous iodide monitoring with high precision, high sample throughput and applicability for quality control of pharmaceuticals and environmental monitoring. Full article

In silicon–carbon (Si-C) anode materials fabricated via chemical vapor deposition (CVD), the pore size distribution of porous carbon is a critical parameter that strongly affects the overall electrochemical performance. In this study, biomass-derived hard carbon was employed as the precursor, and porous carbon materials with distinct pore size characteristics were prepared via fluidized bed porosimetry after carbonization at different temperatures. Based on these porous carbon substrates, three types of Si-C anodes corresponding to low-, medium-, and high-temperature treatments were synthesized through a combination of SiH₄ deposition and carbon coating processes. Electrochemical evaluation demonstrated that all three Si-C anodes exhibited favorable electrochemical performance and suppressed volume expansion. Among them, the Si-C anode prepared at a medium temperature of 1100 °C, denoted as NT-P-SC, delivered the most balanced performance, achieving an initial coulombic efficiency of 94.47% together with excellent rate capability. Furthermore, when Si-C anodes derived from different porous carbon matrices were blended with graphite to achieve a composite capacity of 500 mAh/g and evaluated in full-cell configurations, the NT-P-SC silicon-based composite exhibited superior cycling stability. The composite delivered an initial discharge capacity of 3.53 mAh and maintained a capacity of 2.74 mAh after 1628 cycles, corresponding to a capacity retention of 77.62%. The improved electrochemical performance of the Si-C anode is primarily attributed to the optimized pore structure of the porous carbon matrix synergistically combined with the carbon coating process. Full article

This paper presents a dual four-port circularly polarized (CP) MIMO antenna based on substrate integrated waveguide (SIW) technology for sub-6 GHz applications. The design consists of two identical four-port SIW-based CP-MIMO antennas arranged in a mirror-symmetric configuration with an air gap of 15 mm. Each antenna employs four symmetrically arranged cross-shaped SIW patches excited by coaxial probes. Bidirectional radiation is achieved by applying a 180° phase difference between corresponding ports of the mirror symmetric configuration, referred to as the Backward-Radiating Unit (BRU) and the Forward-Radiating Unit (FRU). The bidirectional radiation mechanism is supported by array-factor-based theoretical modelling, which explains the constructive and destructive interference under phase-controlled excitation. To ensure high isolation and stable polarization performance, the antenna design incorporates defected ground structures, inter-element decoupling strips, and vertical metallic vias. Simulations indicate an operating band from 5.1 to 5.4 GHz. Measurements show a −10 dB bandwidth from 5.25 to 5.55 GHz, with the frequency shift attributed to fabrication tolerances and measurement uncertainties. The antenna achieves inter-port isolation better than −15 dB. A 3 dB axial-ratio bandwidth is maintained across the operating band. Measured axial-ratio values remain below 3 dB from 5.25 to 5.55 GHz, while simulations predict a corresponding range from 5.1 to 5.4 GHz. The proposed configuration achieves a peak gain exceeding 4 dBi and maintains an envelope correlation coefficient below 0.05. These results confirm its suitability for CP-MIMO systems with controlled spatial coverage. With a physical size of 0.733λ₀ × 0.733λ₀ per array, the proposed antenna is well-suited for vehicular and space-constrained wireless systems requiring bidirectional CP-MIMO coverage. Full article

Widely used in treating oil mist aerosols generated from metalworking processes, conventional gas–liquid coalescing filters face drawbacks such as increased energy consumption, performance limitations, and shortened service life due to high steady-state pressure drop. To address these issues, this study proposes an innovative design for a filter based on wettability-regulated gradient pore structure. Using glass fiber filter media with different pore size parameters as the substrate and incorporating an intermediate mesh layer, a three-layer filtration structure of “large-pore filtration layer—mesh layer—small-pore filtration layer” was constructed. The surface wettability of each layer was regulated by a self-developed surface modifier, producing gradient pore structure filters with different wettability configurations. The variations in key performance parameters, including steady-state pressure drop, filtration efficiency, saturation, and service life, were systematically evaluated for these configurations. Experimental results demonstrated that the configuration with an “oleophobic large-pore filtration layer—mesh layer—oleophilic small-pore filtration layer” yielded the best overall performance. Analysis based on the “jump-channel” model indicated that the gradient pore structure achieves progressive droplet filtration and optimizes droplet coalescence and capture through wettability differences. Consequently, while maintaining exceptional filtration efficiency (>99%), this configuration significantly reduces the steady-state pressure drop by over 34% and effectively extends the service life by more than 66%. This wettability-regulated gradient pore structure provides a novel technical pathway for addressing the challenges of balancing pressure drop and filtration efficiency, as well as extending the service life, in gas–liquid coalescing filters. Full article

To advance “bamboo-as-plastic-substitute” initiatives and the sustainable use of furniture materials, this study investigates flattened bamboo sheets by determining their principal-direction elastic constants and evaluating two common furniture T-joints—dowel-jointed panel-type and right-angle mortise-and-tenon frame-type—through tensile and bending load-bearing tests alongside finite element (FE) comparisons. The results show a pronounced anisotropy, with the longitudinal elastic modulus markedly higher than in other directions. At the joint level, the average ultimate load-bearing capacities were 4.06 kN (panel-type tension), 3.70 kN (frame-type tension), 0.264 kN (panel-type bending), and 0.589 kN (frame-type bending). Under identical structural configurations and boundary conditions, the tensile and bending capacities of flattened bamboo sheets were comparable to or exceeded those of the comparator materials (MDF, cherry wood, bamboo-based composites), and failures predominantly occurred in the adhesive layer rather than the bamboo substrate. Across four representative cases, FE predictions achieved a mean absolute percentage error (MAPE) of 6.5% with a maximum relative error of 12.5%; the regression correlation was R² ≈ 0.999 based on four paired observations, which should be interpreted with caution due to the small sample size. The study validates that FE models driven by experimentally measured anisotropic parameters can effectively reproduce the mechanical response of flattened bamboo T-joints, providing a basis for structural design, lightweighting, and parameter optimization in furniture applications. Further work should characterize adhesive systems, environmental durability, and interfacial failure mechanisms to enhance the model’s general applicability. Full article

We investigate crosstalk effects in a dual-modality tactile–proximity sensing system based on Time-of-Flight (ToF) technology integrated within a flat poly(methyl methacrylate) (PMMA) light guide. Building on the OptoSkin framework, we employ two commercially available TMF8828 multi-zone ToF sensors, one configured for tactile detection via frustrated total internal reflection (FTIR) and the other for external proximity measurements through the same transparent substrate. Controlled experiments were conducted using a 2 cm² silicone pad for tactile interaction and an A4-sized diffuse white target for proximity detection. Additional measurements with a movable PMMA sheet were performed to quantify signal attenuation, peak broadening, and confidence degradation under transparent-substrate conditions. The results demonstrate that the TMF8828 can simultaneously resolve both contact-induced scattering and distant reflections, but that localized interference zones occur when sensor fields of view overlap within the substrate. Histogram analysis reveals the underlying multi-path contributions, providing diagnostic insight not available from black-box ToF devices. These findings highlight both the opportunities and limitations of integrating multiple ToF sensors into transparent waveguides and inform design strategies for scalable robotic skins, wearable interfaces, and multi-modal human–machine interaction systems. Full article